I have a GE L-640 which has had all of the caps and resistors replaced by a previous owner. The radio comes on and gets great reception, BUT the volume coming from the speaker is very low and is not affected at all by the volume knob. Moving, wiggling.. nothing. No affect to the sound at all. Judging by other posts in this forum, Im a little out of my league here but I have been able to perform some little repairs successfully so Im hoping to find a possible reason why this could be happening and how to fix it. It almost seems like the resistance set by the volume control was replaced by a resistor but the volume control appears to be wired like the schematic calls for.
Any ideas are appreciated (I've been searching the web and reading a LOT of stuff with no luck. Thanks in advance. -Bob
:
:I have a GE L-640 which has had all of the caps and resistors replaced by a previous owner. The radio comes on and gets great reception, BUT the volume coming from the speaker is very low and is not affected at all by the volume knob. Moving, wiggling.. nothing. No affect to the sound at all. Judging by other posts in this forum, Im a little out of my league here but I have been able to perform some little repairs successfully so Im hoping to find a possible reason why this could be happening and how to fix it. It almost seems like the resistance set by the volume control was replaced by a resistor but the volume control appears to be wired like the schematic calls for.
:
:Any ideas are appreciated (I've been searching the web and reading a LOT of stuff with no luck. Thanks in advance. -Bob
:
Clean your radio/phono switch; I think it's a pushbutton switch. Turn the volume down before powering up the radio.
Johnnysan-
::HI.
::
::I have a GE L-640 which has had all of the caps and resistors replaced by a previous owner. The radio comes on and gets great reception, BUT the volume coming from the speaker is very low and is not affected at all by the volume knob. Moving, wiggling.. nothing. No affect to the sound at all. Judging by other posts in this forum, Im a little out of my league here but I have been able to perform some little repairs successfully so Im hoping to find a possible reason why this could be happening and how to fix it. It almost seems like the resistance set by the volume control was replaced by a resistor but the volume control appears to be wired like the schematic calls for.
::
::Any ideas are appreciated (I've been searching the web and reading a LOT of stuff with no luck. Thanks in advance. -Bob
::
:
:
:Clean your radio/phono switch; I think it's a pushbutton switch. Turn the volume down before powering up the radio.
:Johnnysan-
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:I have a GE L-640 which has had all of the caps and resistors replaced by a previous owner. The radio comes on and gets great reception, BUT the volume coming from the speaker is very low and is not affected at all by the volume knob. Moving, wiggling.. nothing. No affect to the sound at all. Judging by other posts in this forum, Im a little out of my league here but I have been able to perform some little repairs successfully so Im hoping to find a possible reason why this could be happening and how to fix it. It almost seems like the resistance set by the volume control was replaced by a resistor but the volume control appears to be wired like the schematic calls for.
:
:Any ideas are appreciated (I've been searching the web and reading a LOT of stuff with no luck. Thanks in advance. -Bob
:
Clean your radio/phono switch; I think it's a pushbutton switch. Turn the volume down before powering up the radio.
Johnnysan-
:
:I have a GE L-640 which has had all of the caps and resistors replaced by a previous owner. The radio comes on and gets great reception, BUT the volume coming from the speaker is very low and is not affected at all by the volume knob. Moving, wiggling.. nothing. No affect to the sound at all. Judging by other posts in this forum, Im a little out of my league here but I have been able to perform some little repairs successfully so Im hoping to find a possible reason why this could be happening and how to fix it. It almost seems like the resistance set by the volume control was replaced by a resistor but the volume control appears to be wired like the schematic calls for.
:
:Any ideas are appreciated (I've been searching the web and reading a LOT of stuff with no luck. Thanks in advance. -Bob
:
Hope this helps.
Terry
::
::I have a GE L-640 which has had all of the caps and resistors replaced by a previous owner. The radio comes on and gets great reception, BUT the volume coming from the speaker is very low and is not affected at all by the volume knob. Moving, wiggling.. nothing. No affect to the sound at all. Judging by other posts in this forum, Im a little out of my league here but I have been able to perform some little repairs successfully so Im hoping to find a possible reason why this could be happening and how to fix it. It almost seems like the resistance set by the volume control was replaced by a resistor but the volume control appears to be wired like the schematic calls for.
::
::Any ideas are appreciated (I've been searching the web and reading a LOT of stuff with no luck. Thanks in advance. -Bob
::
:
:This COULD, (and I'm not saying IS), be a shorted or leaky cap. Does it have one of those "compensator" caps across the output? How about a grid bias resistor that changed value? The coupling cap from the detector to the output? I'd pull all of the leads off of the control and see what it does using an analogue meter.
:Hope this helps.
:Terry
:
:::
:::I have a GE L-640 which has had all of the caps and resistors replaced by a previous owner. The radio comes on and gets great reception, BUT the volume coming from the speaker is very low and is not affected at all by the volume knob. Moving, wiggling.. nothing. No affect to the sound at all. Judging by other posts in this forum, Im a little out of my league here but I have been able to perform some little repairs successfully so Im hoping to find a possible reason why this could be happening and how to fix it. It almost seems like the resistance set by the volume control was replaced by a resistor but the volume control appears to be wired like the schematic calls for.
:::
:::Any ideas are appreciated (I've been searching the web and reading a LOT of stuff with no luck. Thanks in advance. -Bob
:::
::
::This COULD, (and I'm not saying IS), be a shorted or leaky cap. Does it have one of those "compensator" caps across the output? How about a grid bias resistor that changed value? The coupling cap from the detector to the output? I'd pull all of the leads off of the control and see what it does using an analogue meter.
::Hope this helps.
::Terry
::
:
::::
::::I have a GE L-640 which has had all of the caps and resistors replaced by a previous owner. The radio comes on and gets great reception, BUT the volume coming from the speaker is very low and is not affected at all by the volume knob. Moving, wiggling.. nothing. No affect to the sound at all. Judging by other posts in this forum, Im a little out of my league here but I have been able to perform some little repairs successfully so Im hoping to find a possible reason why this could be happening and how to fix it. It almost seems like the resistance set by the volume control was replaced by a resistor but the volume control appears to be wired like the schematic calls for.
::::
::::Any ideas are appreciated (I've been searching the web and reading a LOT of stuff with no luck. Thanks in advance. -Bob
::::
:::
:::This COULD, (and I'm not saying IS), be a shorted or leaky cap. Does it have one of those "compensator" caps across the output? How about a grid bias resistor that changed value? The coupling cap from the detector to the output? I'd pull all of the leads off of the control and see what it does using an analogue meter.
:::Hope this helps.
:::Terry
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if you short the tube grid to ground? Short the center tap of the volume control to ground? Short the center of the volume control to high side of volume control? Short across the volume control? Try these things, and we'll have a better idea of where to go from here.
Lewis
:::::HI.
:::::
:::::I have a GE L-640 which has had all of the caps and resistors replaced by a previous owner. The radio comes on and gets great reception, BUT the volume coming from the speaker is very low and is not affected at all by the volume knob. Moving, wiggling.. nothing. No affect to the sound at all. Judging by other posts in this forum, Im a little out of my league here but I have been able to perform some little repairs successfully so Im hoping to find a possible reason why this could be happening and how to fix it. It almost seems like the resistance set by the volume control was replaced by a resistor but the volume control appears to be wired like the schematic calls for.
:::::
:::::Any ideas are appreciated (I've been searching the web and reading a LOT of stuff with no luck. Thanks in advance. -Bob
:::::
::::
::::This COULD, (and I'm not saying IS), be a shorted or leaky cap. Does it have one of those "compensator" caps across the output? How about a grid bias resistor that changed value? The coupling cap from the detector to the output? I'd pull all of the leads off of the control and see what it does using an analogue meter.
::::Hope this helps.
::::Terry
::::
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:I got to learn that you don't hit the "enter" key when you are starting with your name, it posts nothing.
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:O. K. now, lesee What happens if you put something in the phono jack and touch it with your finger (switch in phono position, of course)? Does the volume control work then? Do you lose the audio
:if you short the tube grid to ground? Short the center tap of the volume control to ground? Short the center of the volume control to high side of volume control? Short across the volume control? Try these things, and we'll have a better idea of where to go from here.
:Lewis
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Wire in phono jack, radio on phono, touch the wire and nothing. No sound so no volume control. I even put an audio input into the jack and I get no sound. Someone else mentioned the phono switch, maybe you are both onto something there.
Center tap of volume control to ground: No effect.
Center of volume control to high side: No effect.
Short across the volume control: No effect.
Now when it comes to shorting the tube grid to ground, well this is where I fall into the "Amateur Question" catagory. I don't think I know enough regarding which is the grid wire, and I know there's some pretty high voltage in there.
So... I'm going to research the switch for the phono control because I know there obviously is a problem there and maybe the two are related (hopefully).
I want to know what Im touch before I touch any wires going into the tube socket.
Thank you for the ideas and if anything I said gives you another idea, bring it on! THANK you so much. -Bob
:O. K. now, lesee What happens if you put something in the phono jack and touch it with your finger (switch in phono position, of course)? Does the volume control work then? Do you lose the audio
:if you short the tube grid to ground? Short the center tap of the volume control to ground? Short the center of the volume control to high side of volume control? Short across the volume control? Try these things, and we'll have a better idea of where to go from here.
:Lewis
:
:
:
Hope that helps! Thanks again. -Bob
::O. K. now, lesee What happens if you put something in the phono jack and touch it with your finger (switch in phono position, of course)? Does the volume control work then? Do you lose the audio
::if you short the tube grid to ground? Short the center tap of the volume control to ground? Short the center of the volume control to high side of volume control? Short across the volume control? Try these things, and we'll have a better idea of where to go from here.
::Lewis
::
::
::
:
Some preliminaries: The sets tone control assuredly has already been moved around, but does the positioning of that separate tone control have any noticable effect on the volume level. Standing by . . . . and contemplating |
::HI.
::
::I have a GE L-640 which has had all of the caps and resistors replaced by a previous owner. The radio comes on and gets great reception, BUT the volume coming from the speaker is very low and is not affected at all by the volume knob. Moving, wiggling.. nothing. No affect to the sound at all. Judging by other posts in this forum, Im a little out of my league here but I have been able to perform some little repairs successfully so Im hoping to find a possible reason why this could be happening and how to fix it. It almost seems like the resistance set by the volume control was replaced by a resistor but the volume control appears to be wired like the schematic calls for.
::
::Any ideas are appreciated (I've been searching the web and reading a LOT of stuff with no luck. Thanks in advance. -Bob
::
:
:This COULD, (and I'm not saying IS), be a shorted or leaky cap. Does it have one of those "compensator" caps across the output? How about a grid bias resistor that changed value? The coupling cap from the detector to the output? I'd pull all of the leads off of the control and see what it does using an analogue meter.
:Hope this helps.
:Terry
:
Some answers:
Some soldering was done when the resistors and caps were replaced but everything seems to be where it belongs. It does make the full 270 deg rotation smoothly.
I have zipped the vol from one extreme to the other, bass and treble remain the same. It's as if I wasn't doing anything.
Bass and treble do correctly fluctuate when I turn the tone knob (incorporated with on/off switch).
If I had to guess, I'd say the volume is at about 10%. You can hear it and tune a station so it's loud enough for that, but really you have to be very close to hear it clearly. It should go MUCH louder (judging by the volume on my GE J-71).
Testee . . .testee: |
:Thanks for the responses!
:Some answers:
:Some soldering was done when the resistors and caps were replaced but everything seems to be where it belongs. It does make the full 270 deg rotation smoothly.
:
:I have zipped the vol from one extreme to the other, bass and treble remain the same. It's as if I wasn't doing anything.
:
:Bass and treble do correctly fluctuate when I turn the tone knob (incorporated with on/off switch).
:
:If I had to guess, I'd say the volume is at about 10%. You can hear it and tune a station so it's loud enough for that, but really you have to be very close to hear it clearly. It should go MUCH louder (judging by the volume on my GE J-71).
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Yellow wire from 2nd IF xformer to 1st grid of 6SQ7: Volume goes almost completely off. Barely hearable.
Same lead to 1st grid of 6V6 output toobie and the volume bumps UP a touch, a little louder.
Whatcha think? Thanks again for your help. -Bob
|
:Hi Edd. Learning as we go here, scouring the internet to get your answers. I appreciate the questions.
:
:Yellow wire from 2nd IF xformer to 1st grid of 6SQ7: Volume goes almost completely off. Barely hearable.
:
:Same lead to 1st grid of 6V6 output toobie and the volume bumps UP a touch, a little louder.
:
:Whatcha think? Thanks again for your help. -Bob
:
I looked up the values, one is silver/red/green/gold, the other is red/black/green/gold.
If I'm figuring this correctly, thats 10,200k or 10,200,000 ohms. The schematic calls for a 1 megaohm resistor which if Im not mistaken would be 1,000,000 ohms. So either Im wrong or there's 10 times too much resistance? So that could be the problem, right?
Also I did swap out a known good 6SQ7 from my J-71 but it made no difference. Of course that was before the switch was fixed but I'll wait to see what you think about the resistor before I do anything else.
Retiring for the evening, again I appreciate you sharing your knowledge with me. -Bob
Powered up and volume is notably LOUDER probably about 50% now.
Now, when I run the jumper (with cap) from yellow wire to grid 1 on 6SQ7 the sound dies.
When I run the jumper to grid 1 on 6V6, volume cuts in half.
And for the record even though I know everything is making contact in the switch, the phono jack still doesn't react to incoming signal.
Still confused but learning and glad the switch is fixed...
Any ideas are welcome!! Thanks, Bob
:Hi Edd. Learning as we go here, scouring the internet to get your answers. I appreciate the questions.
:
:Yellow wire from 2nd IF xformer to 1st grid of 6SQ7: Volume goes almost completely off. Barely hearable.
:
:Same lead to 1st grid of 6V6 output toobie and the volume bumps UP a touch, a little louder.
:
:Whatcha think? Thanks again for your help. -Bob
:
:
:Powered up and volume is notably LOUDER probably about 50% now.
:
:Now, when I run the jumper (with cap) from yellow wire to grid 1 on 6SQ7 the sound dies.
:
:When I run the jumper to grid 1 on 6V6, volume cuts in half.
:
:And for the record even though I know everything is making contact in the switch, the phono jack still doesn't react to incoming signal.
:
:Still confused but learning and glad the switch is fixed...
:
:Any ideas are welcome!! Thanks, Bob
:
::Hi Edd. Learning as we go here, scouring the internet to get your answers. I appreciate the questions.
::
::Yellow wire from 2nd IF xformer to 1st grid of 6SQ7: Volume goes almost completely off. Barely hearable.
::
::Same lead to 1st grid of 6V6 output toobie and the volume bumps UP a touch, a little louder.
::
::Whatcha think? Thanks again for your help. -Bob
::
:
Many of the older combo radio/phono sets used a cartridge that had a fairly high level output; some were over 5 volts. Modern cartridges have an output much lower (maybe 20 times lower). You must take this into account when testing the phono input. Also, your cartridge could well be bad; many of them failed just from age--so don't trust that it is working (they can be rebuilt). If you touch the phono input and hear just a slight hum, it may be working properly.
Johnnysan-
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Powered up and volume is notably LOUDER probably about 50% now. Now, when I run the jumper (with cap) from yellow wire to grid 1 on 6SQ7 the sound dies. When I run the jumper to grid 1 on 6V6, volume cuts in half. And for the record even though I know everything is making contact in the switch, the phono jack still doesn't react to incoming signal. Still confused but learning and glad the switch is fixed... Any ideas are welcome!! Thanks, Bob
Follow up: I took a closer look at the phono switch and it wasn't so much dirty as it was broken. I had to borrow a slider from one of presets to replace the broken piece and repair some of the contacts but got it back together.
Many of the older combo radio/phono sets used a cartridge that had a fairly high level output; some were over 5 volts. Modern cartridges have an output much lower (maybe 20 times lower). You must take this into account when testing the phono input. Also, your cartridge could well be bad; many of them failed just from age--so don't trust that it is working (they can be rebuilt). If you touch the phono input and hear just a slight hum, it may be working properly.
Johnnysan-
As far as the volume goes, it WAS a different station that seemed stronger so maybe thats why it sounded louder. Im going to work on the other things you discussed and let you know what I find. Thanks again for your insight. -Bob
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:Sir BoB Sssssssssssssss . . . . . .
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:Soooo . . .If you had an open circuit . . . basically from the detected audio from theYELLOW wire and now after phono switch repair, have it going thru to the volume control, that should be no better than the initial routing of the YELLOW wire thru an off board coupling capacitor to the 6SQ7 first grid .
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:The only extra parts involved would be the signals series passage thru the C37 coupling capacitor and the C22 HF bypass capacitor that is not being shorted nor leaky to ground ?
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:Also . . . did the queries on the 6SQ7 associated parts and its plate voltage presence pass muster ?
:
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:How about just ohmming from the 1st grid of the 6SQ7 to ground . . . something is knocking out our audio in that stage. That should at least let us know if someone in the past replaced that 'Q7's grid resistor with a brown-green-black instead of a brown-black-green . . . or maybe it was being a higher resistor vaue of . . . brown-blue-black being used instead of a brown-black-blue.
:
:
:Now if you have confirmed the 'Q7 tube being good, the plate voltage presence and there being no wiring errors, one could check from the plate of the unit over to the grid circuitry of the 6V6 by the use of an ~.05 cap being used for isolation and then clip leading one lead to the ungrounded filament supply for the 'Q7 and then touch the other lead of the capacitor to the 1st grid of the 6V6 and listen for the hummmmmmm, then move the wire to the plate of the 'Q7 and listen for the hummmmmm.
:
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:Then place the caps wire on the 1st grid of the Q7 and run the . . . (probably now set to the max) . . .volume control back about to the 80 % setting to differentiate if the hummm ? volume changes any. IF any healthy level of hummmm is even now being present? (I am thinking of some circuitry tie in to the high side of the volume control that might be pulling down the signal.)
:
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:Pull the 'Q7 tube and inspect all of its octal sockets internal pin connections for confirming no broken or floating internal connections.
:
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:And you did see the light of its filament, and not having a broken keyway and the tube being plugged in 7 of its other possible combinations ?
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:Just now final checking and see your comeback and add on of :
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:So the R10 resistor... what is there was replaced by someone other than me. What's in there are two resistors wired parallel.
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:I looked up the values, one is silver/red/green/gold, the other is red/black/green/gold.
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:OK on analyzing of those values color codings , the second one would be valid with a red/black/green/gold, with it being a 2 megohm 5% tolerance resistor.
:
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:With the silver/red/green/gold . . that won't compute . . but a misread of the silver actually being a white or gray will work, with the white/red/greem/gold being an odd 9.2 megohm at 5% tolerance unit. The other gray/red/green/gold would be the more commonly used 8.2 megohm 5% unit.
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:And a 2 megohm paralleled with that 8.2 megohm would set you right at 1.6 meg which would be putting you 600k above that 1 meg desired target value.
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:However, if that first resistor happened to be a red/green/gold /silver or even a red/green/silver/gold , that would be a very low ohmic value resistor or sub one ohm resistor value.
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:And that could certainly be your problem, with the 6SQ7 plate not tolerating that plate voltage that would be supplied..
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:Sooooo you really need to ohm out those two resistors combined value, but if resulting as to being the 1.6 meg value . . . that would NOT be the real clincher to the existing problem.
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:73's de Edd
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:Follow up: I took a closer look at the phono switch and it wasn't so much dirty as it was broken. I had to borrow a slider from one of presets to replace the broken piece and repair some of the contacts but got it back together.
:
:Powered up and volume is notably LOUDER probably about 50% now.
:
:Now, when I run the jumper (with cap) from yellow wire to grid 1 on 6SQ7 the sound dies.
:
:When I run the jumper to grid 1 on 6V6, volume cuts in half.
:
:And for the record even though I know everything is making contact in the switch, the phono jack still doesn't react to incoming signal.
:
:Still confused but learning and glad the switch is fixed...
:
:Any ideas are welcome!! Thanks, Bob
:
:
:
:
:
:
:Hi Edd. Learning as we go here, scouring the internet to get your answers. I appreciate the questions.
:
:Yellow wire from 2nd IF xformer to 1st grid of 6SQ7: Volume goes almost completely off. Barely hearable.
:
:Same lead to 1st grid of 6V6 output toobie and the volume bumps UP a touch, a little louder.
:
:Whatcha think? Thanks again for your help. -Bob
:
:
:
:
:
:
:Many of the older combo radio/phono sets used a cartridge that had a fairly high level output; some were over 5 volts. Modern cartridges have an output much lower (maybe 20 times lower). You must take this into account when testing the phono input. Also, your cartridge could well be bad; many of them failed just from age--so don't trust that it is working (they can be rebuilt). If you touch the phono input and hear just a slight hum, it may be working properly.
:Johnnysan-
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:
http://www.mgnewbie.com/radiohelp.html
Now lets see. THe 6SQ7 I have is metal so I can't see if it's glowing but it sure gets warm. I also swapped one from a radio that's working but it didn't make a difference. The socket connections seem clean and tight. The tab is still on the tube so it should be correctly installed.
C22 does not have continuity between the two terminals so I assume it's not shorted to ground. C37, from my photos and diagrams... is it missing or am I missing something?
Plate voltage on 6SQ7. Is that the voltage that heats the element? Because let me tell you, I was going to put my volt meter on that but just touching my lead to the ground side of that (nothing attached to the other end) caused some wicked (and very loud) static. I got nervous because I don't feel like killing myself and thought it best not to go there just yet.
Here's what I see. The ground from the volume control goes directly to 6SQ7 pin 8 (cathode?) and pin 1 (grid 3?), then jump through those parallel resistors we discussed prior to pin 2 which should be the ground for the heater. SHould pin 8 and 1 be jumped? It's hard for me to tell by the schematic.
Ohmming from Q7 grid one to ground there is 0 resistance and I get the continuity beep from my digital mulitmeter, which you probably already figured from my last paragraph but I just realized what Im tesing is what I just pointed OUT!
So I think I answered all of your question except for the from the "plate of the unit to grid circuitry on 6V6"... To be honest, Im not sure what the plate of the unit is and I don't want to blow it (or myself) up...
I hope that helps, and once again I really appreciate your help with this mystery!!
Thanks, Bob
:Hi Edd. I didn't forget.. just been busy. To answer the second part, what I thought was silver was indeed gray, meaning that we are at 1.6 meg which would not be the smoking gun if Im understanding correctly.
:
:As far as the volume goes, it WAS a different station that seemed stronger so maybe thats why it sounded louder. Im going to work on the other things you discussed and let you know what I find. Thanks again for your insight. -Bob
:
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::Sir BoB Sssssssssssssss . . . . . .
::
::
::Soooo . . .If you had an open circuit . . . basically from the detected audio from theYELLOW wire and now after phono switch repair, have it going thru to the volume control, that should be no better than the initial routing of the YELLOW wire thru an off board coupling capacitor to the 6SQ7 first grid .
::
::
::The only extra parts involved would be the signals series passage thru the C37 coupling capacitor and the C22 HF bypass capacitor that is not being shorted nor leaky to ground ?
::
::
::Also . . . did the queries on the 6SQ7 associated parts and its plate voltage presence pass muster ?
::
::
::How about just ohmming from the 1st grid of the 6SQ7 to ground . . . something is knocking out our audio in that stage. That should at least let us know if someone in the past replaced that 'Q7's grid resistor with a brown-green-black instead of a brown-black-green . . . or maybe it was being a higher resistor vaue of . . . brown-blue-black being used instead of a brown-black-blue.
::
::
::Now if you have confirmed the 'Q7 tube being good, the plate voltage presence and there being no wiring errors, one could check from the plate of the unit over to the grid circuitry of the 6V6 by the use of an ~.05 cap being used for isolation and then clip leading one lead to the ungrounded filament supply for the 'Q7 and then touch the other lead of the capacitor to the 1st grid of the 6V6 and listen for the hummmmmmm, then move the wire to the plate of the 'Q7 and listen for the hummmmmm.
::
::
::Then place the caps wire on the 1st grid of the Q7 and run the . . . (probably now set to the max) . . .volume control back about to the 80 % setting to differentiate if the hummm ? volume changes any. IF any healthy level of hummmm is even now being present? (I am thinking of some circuitry tie in to the high side of the volume control that might be pulling down the signal.)
::
::
::Pull the 'Q7 tube and inspect all of its octal sockets internal pin connections for confirming no broken or floating internal connections.
::
::
::And you did see the light of its filament, and not having a broken keyway and the tube being plugged in 7 of its other possible combinations ?
::
::
::
::
::Just now final checking and see your comeback and add on of :
::
::
::
::So the R10 resistor... what is there was replaced by someone other than me. What's in there are two resistors wired parallel.
::
::
::I looked up the values, one is silver/red/green/gold, the other is red/black/green/gold.
::
::
::
::OK on analyzing of those values color codings , the second one would be valid with a red/black/green/gold, with it being a 2 megohm 5% tolerance resistor.
::
::
::With the silver/red/green/gold . . that won't compute . . but a misread of the silver actually being a white or gray will work, with the white/red/greem/gold being an odd 9.2 megohm at 5% tolerance unit. The other gray/red/green/gold would be the more commonly used 8.2 megohm 5% unit.
::
::
::And a 2 megohm paralleled with that 8.2 megohm would set you right at 1.6 meg which would be putting you 600k above that 1 meg desired target value.
::
::
::However, if that first resistor happened to be a red/green/gold /silver or even a red/green/silver/gold , that would be a very low ohmic value resistor or sub one ohm resistor value.
::
::
::And that could certainly be your problem, with the 6SQ7 plate not tolerating that plate voltage that would be supplied..
::
::
::Sooooo you really need to ohm out those two resistors combined value, but if resulting as to being the 1.6 meg value . . . that would NOT be the real clincher to the existing problem.
::
::
::
::
::73's de Edd
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::
::Follow up: I took a closer look at the phono switch and it wasn't so much dirty as it was broken. I had to borrow a slider from one of presets to replace the broken piece and repair some of the contacts but got it back together.
::
::Powered up and volume is notably LOUDER probably about 50% now.
::
::Now, when I run the jumper (with cap) from yellow wire to grid 1 on 6SQ7 the sound dies.
::
::When I run the jumper to grid 1 on 6V6, volume cuts in half.
::
::And for the record even though I know everything is making contact in the switch, the phono jack still doesn't react to incoming signal.
::
::Still confused but learning and glad the switch is fixed...
::
::Any ideas are welcome!! Thanks, Bob
::
::
::
::
::
::
::Hi Edd. Learning as we go here, scouring the internet to get your answers. I appreciate the questions.
::
::Yellow wire from 2nd IF xformer to 1st grid of 6SQ7: Volume goes almost completely off. Barely hearable.
::
::Same lead to 1st grid of 6V6 output toobie and the volume bumps UP a touch, a little louder.
::
::Whatcha think? Thanks again for your help. -Bob
::
::
::
::
::
::
::Many of the older combo radio/phono sets used a cartridge that had a fairly high level output; some were over 5 volts. Modern cartridges have an output much lower (maybe 20 times lower). You must take this into account when testing the phono input. Also, your cartridge could well be bad; many of them failed just from age--so don't trust that it is working (they can be rebuilt). If you touch the phono input and hear just a slight hum, it may be working properly.
::Johnnysan-
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::
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::
:
GOOOOOOD thoroughness on your feedback ! http://www.mgnewbie.com/radiohelp.html Fill us in on the continuity flow of the [Fuchsia arrow path], and if that is complete, then I was thinking of the extreme condition of there being no plate voltage on the 'Q7 or its 1st grid voluconnection being in a grounded or quasi grounded condition. [Nope #8 is one lead of the filament supply, which needs to be grounded . . . so it IS providing a ground connection ] and pin 1 (grid 3?) [Nope . . .that #1 would be inner connecting to that floating metal shield around the envelope of the 'Q7 , and its #3 is cathode] which is needing to be grounded . Should pin 8 and 1 be jumped? It's hard for me to tell by the schematic. [Yes, and also both being grounded] |
:Hi Edd. I have some more info for you, hopefully I am able to answer your questions. And remember I'm an amateur so maybe Im seeing something wrong. But here's what I see regarding C22 and C37:
:
:http://www.mgnewbie.com/radiohelp.html
:
:Now lets see. THe 6SQ7 I have is metal so I can't see if it's glowing but it sure gets warm. I also swapped one from a radio that's working but it didn't make a difference. The socket connections seem clean and tight. The tab is still on the tube so it should be correctly installed.
:
:C22 does not have continuity between the two terminals so I assume it's not shorted to ground. C37, from my photos and diagrams... is it missing or am I missing something?
:
:Plate voltage on 6SQ7. Is that the voltage that heats the element? Because let me tell you, I was going to put my volt meter on that but just touching my lead to the ground side of that (nothing attached to the other end) caused some wicked (and very loud) static. I got nervous because I don't feel like killing myself and thought it best not to go there just yet.
:
:Here's what I see. The ground from the volume control goes directly to 6SQ7 pin 8 (cathode?) and pin 1 (grid 3?), then jump through those parallel resistors we discussed prior to pin 2 which should be the ground for the heater. SHould pin 8 and 1 be jumped? It's hard for me to tell by the schematic.
:
:Ohmming from Q7 grid one to ground there is 0 resistance and I get the continuity beep from my digital mulitmeter, which you probably already figured from my last paragraph but I just realized what Im tesing is what I just pointed OUT!
:
:So I think I answered all of your question except for the from the "plate of the unit to grid circuitry on 6V6"... To be honest, Im not sure what the plate of the unit is and I don't want to blow it (or myself) up...
:
:I hope that helps, and once again I really appreciate your help with this mystery!!
:
:Thanks, Bob
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::Hi Edd. I didn't forget.. just been busy. To answer the second part, what I thought was silver was indeed gray, meaning that we are at 1.6 meg which would not be the smoking gun if Im understanding correctly.
::
::As far as the volume goes, it WAS a different station that seemed stronger so maybe thats why it sounded louder. Im going to work on the other things you discussed and let you know what I find. Thanks again for your insight. -Bob
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:::Sir BoB Sssssssssssssss . . . . . .
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:::Soooo . . .If you had an open circuit . . . basically from the detected audio from theYELLOW wire and now after phono switch repair, have it going thru to the volume control, that should be no better than the initial routing of the YELLOW wire thru an off board coupling capacitor to the 6SQ7 first grid .
:::
:::
:::The only extra parts involved would be the signals series passage thru the C37 coupling capacitor and the C22 HF bypass capacitor that is not being shorted nor leaky to ground ?
:::
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:::Also . . . did the queries on the 6SQ7 associated parts and its plate voltage presence pass muster ?
:::
:::
:::How about just ohmming from the 1st grid of the 6SQ7 to ground . . . something is knocking out our audio in that stage. That should at least let us know if someone in the past replaced that 'Q7's grid resistor with a brown-green-black instead of a brown-black-green . . . or maybe it was being a higher resistor vaue of . . . brown-blue-black being used instead of a brown-black-blue.
:::
:::
:::Now if you have confirmed the 'Q7 tube being good, the plate voltage presence and there being no wiring errors, one could check from the plate of the unit over to the grid circuitry of the 6V6 by the use of an ~.05 cap being used for isolation and then clip leading one lead to the ungrounded filament supply for the 'Q7 and then touch the other lead of the capacitor to the 1st grid of the 6V6 and listen for the hummmmmmm, then move the wire to the plate of the 'Q7 and listen for the hummmmmm.
:::
:::
:::Then place the caps wire on the 1st grid of the Q7 and run the . . . (probably now set to the max) . . .volume control back about to the 80 % setting to differentiate if the hummm ? volume changes any. IF any healthy level of hummmm is even now being present? (I am thinking of some circuitry tie in to the high side of the volume control that might be pulling down the signal.)
:::
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:::Pull the 'Q7 tube and inspect all of its octal sockets internal pin connections for confirming no broken or floating internal connections.
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:::And you did see the light of its filament, and not having a broken keyway and the tube being plugged in 7 of its other possible combinations ?
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:::Just now final checking and see your comeback and add on of :
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:::So the R10 resistor... what is there was replaced by someone other than me. What's in there are two resistors wired parallel.
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:::I looked up the values, one is silver/red/green/gold, the other is red/black/green/gold.
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:::OK on analyzing of those values color codings , the second one would be valid with a red/black/green/gold, with it being a 2 megohm 5% tolerance resistor.
:::
:::
:::With the silver/red/green/gold . . that won't compute . . but a misread of the silver actually being a white or gray will work, with the white/red/greem/gold being an odd 9.2 megohm at 5% tolerance unit. The other gray/red/green/gold would be the more commonly used 8.2 megohm 5% unit.
:::
:::
:::And a 2 megohm paralleled with that 8.2 megohm would set you right at 1.6 meg which would be putting you 600k above that 1 meg desired target value.
:::
:::
:::However, if that first resistor happened to be a red/green/gold /silver or even a red/green/silver/gold , that would be a very low ohmic value resistor or sub one ohm resistor value.
:::
:::
:::And that could certainly be your problem, with the 6SQ7 plate not tolerating that plate voltage that would be supplied..
:::
:::
:::Sooooo you really need to ohm out those two resistors combined value, but if resulting as to being the 1.6 meg value . . . that would NOT be the real clincher to the existing problem.
:::
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:::73's de Edd
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:::
:::Follow up: I took a closer look at the phono switch and it wasn't so much dirty as it was broken. I had to borrow a slider from one of presets to replace the broken piece and repair some of the contacts but got it back together.
:::
:::Powered up and volume is notably LOUDER probably about 50% now.
:::
:::Now, when I run the jumper (with cap) from yellow wire to grid 1 on 6SQ7 the sound dies.
:::
:::When I run the jumper to grid 1 on 6V6, volume cuts in half.
:::
:::And for the record even though I know everything is making contact in the switch, the phono jack still doesn't react to incoming signal.
:::
:::Still confused but learning and glad the switch is fixed...
:::
:::Any ideas are welcome!! Thanks, Bob
:::
:::
:::
:::
:::
:::
:::Hi Edd. Learning as we go here, scouring the internet to get your answers. I appreciate the questions.
:::
:::Yellow wire from 2nd IF xformer to 1st grid of 6SQ7: Volume goes almost completely off. Barely hearable.
:::
:::Same lead to 1st grid of 6V6 output toobie and the volume bumps UP a touch, a little louder.
:::
:::Whatcha think? Thanks again for your help. -Bob
:::
:::
:::
:::
:::
:::
:::Many of the older combo radio/phono sets used a cartridge that had a fairly high level output; some were over 5 volts. Modern cartridges have an output much lower (maybe 20 times lower). You must take this into account when testing the phono input. Also, your cartridge could well be bad; many of them failed just from age--so don't trust that it is working (they can be rebuilt). If you touch the phono input and hear just a slight hum, it may be working properly.
:::Johnnysan-
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:
If I'm looking at a diagram of tube socket connections as this one:
http://en.wikipedia.org/wiki/File:EIA-9A.png
Am I looking down at the connector with the tube REMOVED? Or is this from the bottom up?
Maybe thats why I have everything backwards...
Just checking, I'll be going to work tonight to see what I can find! Thanks, Bob
src=http://www.flickr.com/photos/49009898@N05/4721678572/>
:Quick question before I go any further...
:
:If I'm looking at a diagram of tube socket connections as this one:
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:http://en.wikipedia.org/wiki/File:EIA-9A.png
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:Am I looking down at the connector with the tube REMOVED? Or is this from the bottom up?
:
:Maybe thats why I have everything backwards...
:
:Just checking, I'll be going to work tonight to see what I can find! Thanks, Bob
:
:
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:I think the picture below will explain tube pinout.
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:src="http://www.flickr.com/photos/49009898@N05/4721678572/">
:
::Quick question before I go any further...
::
::If I'm looking at a diagram of tube socket connections as this one:
::
::http://en.wikipedia.org/wiki/File:EIA-9A.png
::
::Am I looking down at the connector with the tube REMOVED? Or is this from the bottom up?
::
::Maybe thats why I have everything backwards...
::
::Just checking, I'll be going to work tonight to see what I can find! Thanks, Bob
::
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:
:No picture in last post.
:
::I think the picture below will explain tube pinout.
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::
::
:::Quick question before I go any further...
:::
:::If I'm looking at a diagram of tube socket connections as this one:
:::
:::http://en.wikipedia.org/wiki/File:EIA-9A.png
:::
:::Am I looking down at the connector with the tube REMOVED? Or is this from the bottom up?
:::
:::Maybe thats why I have everything backwards...
:::
:::Just checking, I'll be going to work tonight to see what I can find! Thanks, Bob
:::
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Just utilize this musing of mine at a verrrry young age: ASIDE: |
:One more try. ::::Quick question before I go any further...
:
::No picture in last post.
::
:::I think the picture below will explain tube pinout.
:::
:::
:::
::::
::::If I'm looking at a diagram of tube socket connections as this one:
::::
::::http://en.wikipedia.org/wiki/File:EIA-9A.png
::::
::::Am I looking down at the connector with the tube REMOVED? Or is this from the bottom up?
::::
::::Maybe thats why I have everything backwards...
::::
::::Just checking, I'll be going to work tonight to see what I can find! Thanks, Bob
::::
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Thanks for fixing the picture. I shouldn't have tried to post it at lunch time as was trying to do the code in a hurry by memory. And yes your right I would be 57 years old. As to sedalia. It is one of my favorite Native American point that I found. I've always used it as my name on Internet sites.
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:Sir . . . . . .Bob . . . . . . Ssssssss
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:Just utilize this musing of mine at a verrrry young age:
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:If I am going to be WORKING on this unit, I could be gleaning absolute minimal information while viewing the chassis from a TOP view, now if I flip it over, WOW ! everything in the world is now showing up in my viewing scape.
:So they certainly meant for one to be working on the set from the bottom chassis aspect and then all of those tube sockets terminals come into view and with ALL of those little thingies all being connected up to them.
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:Now since I have just mastered telling time, seems like they should be doing it the same way ?
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:Now . . . wheres that 12:00 o'clock starting point ? Needless to say, I soon found out that starting point was that little raised seam /key way on the side of the center bakelite column in the center of an octal socket, or the very same treatment on the metal column on loktal tube.
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:Now for the oldie tubies, one found the two LARGE pins and started between them, then came the 7 and nine pin miniature tubes and their missing pin which then left a gap to be the reference.
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:Sir Steve had created a synopsis of all mentioned bottom base profiles in his:
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:(Which I slipped into and acquired from yet another one of its portals . . .with its depictions placed just below)
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:ASIDE:
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:Hmmm . . . now in working on Steves cryptic . . . Sedalia-53 . . . with its obviously immediate Arizona affinity, yet with another variant being its finding in the Farm 2 photo collection, which would then obviate that possible same named variant species of onion genus
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:And could you additionally and possibly be getting into a 57'ish age timeframe ?
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:73's de Edd
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::One more try.
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:::No picture in last post.
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::::I think the picture below will explain tube pinout.
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::::
::::
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:::::Quick question before I go any further...
:::::
:::::If I'm looking at a diagram of tube socket connections as this one:
:::::
:::::http://en.wikipedia.org/wiki/File:EIA-9A.png
:::::
:::::Am I looking down at the connector with the tube REMOVED? Or is this from the bottom up?
:::::
:::::Maybe thats why I have everything backwards...
:::::
:::::Just checking, I'll be going to work tonight to see what I can find! Thanks, Bob
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I should have put the emphasis on AMATEUR in the title.
Thanks, back to work now to see if I can figure out where is the problem.
Thanks again! -Bob
Okay, here’s what I’ve got:
Yellow wire coming out of “T3” on schematic, goes directly to a junction block via wire. Then connected to that junction is resistor “yellow-purple-yellow-gold” which I understand to be 470,000 ohm. The other end of that resistor goes to ground. The schematic says that should be 47,000 ohm. Im assuming that’s R3. Then from the junction to the Aux switch is a wire. There is continuity from the beginning of the yellow wire across the junction and across the phono switch. So far so good.
Now from there it seems to deviate from the schematic…
Soldiered to the terminal LEAVING the phono switch is a capacitor .01uF going into the center connector for the volume control.
Looking at the back of the volume control, the right side goes direct to ground and the right and left terminal are bridged by C22.
Out of the top of the volume comes R14 to C31 to a junction block that has continuity to ground.
Out of curiousity, I disconnected everything (except the ground) from the volume control and the radio still plays at the same volume, which I will estimate at 50% volume?? Guessing.
As you stated, 1,3 and 8 are all connected together and all grounded.
Now, the two resistors in parallel we discussed go from the aforementioned 1,3,8 ground thru the two resistors into pin 2 on ‘Q7.
‘Q7 grid 1 to ground there is NOT continuity. I was wrong there, I did PIN 1.
‘Q7 pin 6 has two of the terminals from the TONE switch going into through capacitors into pin 6.
I wish I had a better grasp on the concepts so I could give you better information about whats going on. My understanding is that the signal should be coming into one end of the volume control at full strength, Im assuming from 2nd IF Transformer yellow wire and then leave the volume control at a reduced level determined by the volume level on the knob. So it seems as if it has been bypassed completely. Like I said, just as an experiment I disconnected everything from the volume control, which Im assuming should just open the circuit (no sound) but the sound was completely unchanged.
I hope this helps, as always thank you for your input, I really appreciate it. -Bob
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:Sir Bob . . . . . .Ssssssssss
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:GOOOOOOD thoroughness on your feedback !
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:http://www.mgnewbie.com/radiohelp.html
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:Looks like your audio signal flow problem is going to be sim- what- sumalar to the like connectivity problem that was eventually found out on that MG-B's fuel gauge.
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:The 6SQ7 I have is metal so I can't see if it's glowing but it sure gets warm
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:The tab is still on the tube so it should be correctly installed.
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:Then, looks like you are just fine in that respect . . . jes' checkin' . . .
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:C37, from my photos and diagrams... is it missing or am I missing something?
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:Referencing to your fotie-graf . . . I am seeing no C37 presence connected to that high end of the vol-you-me control, but there may be use of a interconnecting wire instead and it remotes down towards the phono-radio switch where that cap might be physically installed somewhere within that path.
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:If you will now consult the info provided by my added thumbnail of your sets involved audio circuitry path, I have traced the detected audio path [in Fuchsia color] from the bottom of the secondary of the 2nd IF transformer and its then required circuit flow to then end up at the 1st grid of the 6SQ7. If the C37 is missing then the path is disrupted . . . possibly the last "FIXOR" pulled all of the caps en masse and then overlooked putting that one in with all of the replacements.
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:(HOLY Mackeral ' deah Andy . . . . lets see now . . . I'm going to be workin' on our big radio from the Lodge of the Mystic Knights of the Sea and now it seems like if I pulls out all of these parts and puts in new parts, and 'dis heah radio wuks . . . . seems likes I would be the "FIXOR" and de radio heah be de "FIXEE".
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:Sapphire . . . Sapphire . . .SAPPHIRE !. . . . come in here and listen to this heah radio ! )
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:Now IF that cap is missing completely, you can see why there is no audio getting in to the 1st grid of the 6SQ7 to be amplified and passed on down to the 6V6 to drive the speaker.
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:
:BUT . . SEEMS like I had you taking a clip lead connecting to an isolating ~.05 cap and having its one end then connected to the yellow wire with the incoming audio and then the other caps end feeding either to the 1st grid of the 6SQ7 and then the 6V6 of which, the latter gave you some degree of volume of the incoming stations audio, BUT the connection into the 1st grid of the 6SQ7 should have knocked your socks off with its created volume.
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:Then your:
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:Plate voltage on 6SQ7. Is that the voltage that heats the element?
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:The voltage that heats up the filament is ~6.3 Vac at pins 7 and 8 of the 6SQ7 . . so UR OK on that.
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:The plate voltage is that being drawn up in [Red] up to the plate resistor R10 and then the [Blue] path up to the plate of the 'Q7.
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:In different designs and different tubes I have found that stages plate voltage as low as ~40 or as high as ~75.
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:The principle is for that plate, with its + voltage potential, to attract a stream of electrons from that hot cathode surounding the warmed up filament. With one hindrance, that grid which is in the flow path.
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:If the 1st grid is receiving progressive levels of positive voltage it lets the electrons flyyyyyyyy thru, if starting to receive progressive levels of negative voltage , they are progressively/ proportionally being repelled back/impeded, right there within that grid to cathode area.
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:As the grid voltage swings up and down thru its voltage convolutions of the applied audio signal, the plate voltage swings coordinately . . thus you then have your amplified audio being developed up across that R10 plate resistor.
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:Because let me tell you, I was going to put my volt meter on that but just touching my lead to the ground side of that (nothing attached to the other end) caused some wicked (and very loud) static.
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:Uncertain on the specific semantics of the above statement in relation to circuit connection..
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:But if relevant to the connection of metering connection to actual ground with a battery powered/isolated meter . . . can't see that.
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:If using an AC line powered meter . . . I can see that . . . if the volume is up to its max, and the connection then is creating or upsetting a ground loop.
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:If any floating metering . . . battery powered . . . . single lead is touched to the 'Q67 plate the induced raw signal pick up from the leads could then be amplified by the 6V6 to raise a bit of an initial pop or continual hum if left connected.
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:Fill us in on the continuity flow of the [Fuchsia arrow path], and if that is complete, then I was thinking of the extreme condition of there being no plate voltage on the 'Q7 or its 1st grid voluconnection being in a grounded or quasi grounded condition.
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:
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:Here's what I see. The ground from the volume control goes directly to 6SQ7 pin 8 (cathode?)
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:[Nope #8 is one lead of the filament supply, which needs to be grounded . . . so it IS providing a ground connection ]
:
:and pin 1 (grid 3?)
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: [Nope . . .that #1 would be inner connecting to that floating metal shield around the envelope of the 'Q7 , and its #3 is cathode]
:
:which is needing to be grounded . Should pin 8 and 1 be jumped? It's hard for me to tell by the schematic.
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:[Yes, and also both being grounded]
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:Synopsis . . .en toto . . . Pins 1,3 and 8 are all being inner connected and then getting grounded.
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:" then jump through those parallel resistors we discussed prior to pin 2 which should be the ground for the heater. "
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:
:NOW . . .if I am reading that right . . . that would have the plate of the 'Q7 (#6) is coming down to a set of paralleled resistors that are subbing in as a 1.6 meg replacement/ vice 1 meg for R10 on the schematic and their lower ends are then connecting to ground .
:
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:Now if that is the way it is wired in, then that lower connection pair needs to go to the B+ buss as my red mark up is showing.
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:I'm stopping for need of feedback fill in. . . .also reconfirm the statement below, unless it could be in error merely because you were mis reading tube elements to pin out connections which are now marked up clearly on the submitted working schema.
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:Ohmming from Q7 grid one to ground there is 0 resistance and I get the continuity beep from my digital mulitmeter . . . . .
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:(if so . . . We gots troubles . . .troubles in River city . . right here in River city!)
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:73's de Edd
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::Hi Edd. I have some more info for you, hopefully I am able to answer your questions. And remember I'm an amateur so maybe Im seeing something wrong. But here's what I see regarding C22 and C37:
::
::http://www.mgnewbie.com/radiohelp.html
::
::Now lets see. THe 6SQ7 I have is metal so I can't see if it's glowing but it sure gets warm. I also swapped one from a radio that's working but it didn't make a difference. The socket connections seem clean and tight. The tab is still on the tube so it should be correctly installed.
::
::C22 does not have continuity between the two terminals so I assume it's not shorted to ground. C37, from my photos and diagrams... is it missing or am I missing something?
::
::Plate voltage on 6SQ7. Is that the voltage that heats the element? Because let me tell you, I was going to put my volt meter on that but just touching my lead to the ground side of that (nothing attached to the other end) caused some wicked (and very loud) static. I got nervous because I don't feel like killing myself and thought it best not to go there just yet.
::
::Here's what I see. The ground from the volume control goes directly to 6SQ7 pin 8 (cathode?) and pin 1 (grid 3?), then jump through those parallel resistors we discussed prior to pin 2 which should be the ground for the heater. SHould pin 8 and 1 be jumped? It's hard for me to tell by the schematic.
::
::Ohmming from Q7 grid one to ground there is 0 resistance and I get the continuity beep from my digital mulitmeter, which you probably already figured from my last paragraph but I just realized what Im tesing is what I just pointed OUT!
::
::So I think I answered all of your question except for the from the "plate of the unit to grid circuitry on 6V6"... To be honest, Im not sure what the plate of the unit is and I don't want to blow it (or myself) up...
::
::I hope that helps, and once again I really appreciate your help with this mystery!!
::
::Thanks, Bob
::
::
::
::
::
:::Hi Edd. I didn't forget.. just been busy. To answer the second part, what I thought was silver was indeed gray, meaning that we are at 1.6 meg which would not be the smoking gun if Im understanding correctly.
:::
:::As far as the volume goes, it WAS a different station that seemed stronger so maybe thats why it sounded louder. Im going to work on the other things you discussed and let you know what I find. Thanks again for your insight. -Bob
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::::Sir BoB Sssssssssssssss . . . . . .
::::
::::
::::Soooo . . .If you had an open circuit . . . basically from the detected audio from theYELLOW wire and now after phono switch repair, have it going thru to the volume control, that should be no better than the initial routing of the YELLOW wire thru an off board coupling capacitor to the 6SQ7 first grid .
::::
::::
::::The only extra parts involved would be the signals series passage thru the C37 coupling capacitor and the C22 HF bypass capacitor that is not being shorted nor leaky to ground ?
::::
::::
::::Also . . . did the queries on the 6SQ7 associated parts and its plate voltage presence pass muster ?
::::
::::
::::How about just ohmming from the 1st grid of the 6SQ7 to ground . . . something is knocking out our audio in that stage. That should at least let us know if someone in the past replaced that 'Q7's grid resistor with a brown-green-black instead of a brown-black-green . . . or maybe it was being a higher resistor vaue of . . . brown-blue-black being used instead of a brown-black-blue.
::::
::::
::::Now if you have confirmed the 'Q7 tube being good, the plate voltage presence and there being no wiring errors, one could check from the plate of the unit over to the grid circuitry of the 6V6 by the use of an ~.05 cap being used for isolation and then clip leading one lead to the ungrounded filament supply for the 'Q7 and then touch the other lead of the capacitor to the 1st grid of the 6V6 and listen for the hummmmmmm, then move the wire to the plate of the 'Q7 and listen for the hummmmmm.
::::
::::
::::Then place the caps wire on the 1st grid of the Q7 and run the . . . (probably now set to the max) . . .volume control back about to the 80 % setting to differentiate if the hummm ? volume changes any. IF any healthy level of hummmm is even now being present? (I am thinking of some circuitry tie in to the high side of the volume control that might be pulling down the signal.)
::::
::::
::::Pull the 'Q7 tube and inspect all of its octal sockets internal pin connections for confirming no broken or floating internal connections.
::::
::::
::::And you did see the light of its filament, and not having a broken keyway and the tube being plugged in 7 of its other possible combinations ?
::::
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::::Just now final checking and see your comeback and add on of :
::::
::::
::::
::::So the R10 resistor... what is there was replaced by someone other than me. What's in there are two resistors wired parallel.
::::
::::
::::I looked up the values, one is silver/red/green/gold, the other is red/black/green/gold.
::::
::::
::::
::::OK on analyzing of those values color codings , the second one would be valid with a red/black/green/gold, with it being a 2 megohm 5% tolerance resistor.
::::
::::
::::With the silver/red/green/gold . . that won't compute . . but a misread of the silver actually being a white or gray will work, with the white/red/greem/gold being an odd 9.2 megohm at 5% tolerance unit. The other gray/red/green/gold would be the more commonly used 8.2 megohm 5% unit.
::::
::::
::::And a 2 megohm paralleled with that 8.2 megohm would set you right at 1.6 meg which would be putting you 600k above that 1 meg desired target value.
::::
::::
::::However, if that first resistor happened to be a red/green/gold /silver or even a red/green/silver/gold , that would be a very low ohmic value resistor or sub one ohm resistor value.
::::
::::
::::And that could certainly be your problem, with the 6SQ7 plate not tolerating that plate voltage that would be supplied..
::::
::::
::::Sooooo you really need to ohm out those two resistors combined value, but if resulting as to being the 1.6 meg value . . . that would NOT be the real clincher to the existing problem.
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::::73's de Edd
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::::Follow up: I took a closer look at the phono switch and it wasn't so much dirty as it was broken. I had to borrow a slider from one of presets to replace the broken piece and repair some of the contacts but got it back together.
::::
::::Powered up and volume is notably LOUDER probably about 50% now.
::::
::::Now, when I run the jumper (with cap) from yellow wire to grid 1 on 6SQ7 the sound dies.
::::
::::When I run the jumper to grid 1 on 6V6, volume cuts in half.
::::
::::And for the record even though I know everything is making contact in the switch, the phono jack still doesn't react to incoming signal.
::::
::::Still confused but learning and glad the switch is fixed...
::::
::::Any ideas are welcome!! Thanks, Bob
::::
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::::
::::Hi Edd. Learning as we go here, scouring the internet to get your answers. I appreciate the questions.
::::
::::Yellow wire from 2nd IF xformer to 1st grid of 6SQ7: Volume goes almost completely off. Barely hearable.
::::
::::Same lead to 1st grid of 6V6 output toobie and the volume bumps UP a touch, a little louder.
::::
::::Whatcha think? Thanks again for your help. -Bob
::::
::::
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::::
::::
::::
::::Many of the older combo radio/phono sets used a cartridge that had a fairly high level output; some were over 5 volts. Modern cartridges have an output much lower (maybe 20 times lower). You must take this into account when testing the phono input. Also, your cartridge could well be bad; many of them failed just from age--so don't trust that it is working (they can be rebuilt). If you touch the phono input and hear just a slight hum, it may be working properly.
::::Johnnysan-
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:
Yellow wire from 2nd IF xformer to 6V6 grid 1, sound volume drops by approximately 1/2.
As directed, .05 paper cap inline.
I am tacking this on, way down here, following your final / most current Date Time Group identification. ((( Was photo #3 . . . aka . . ."volume control" JPG ))) So I am seeing the "low" end, right teminal lug of the volume control going to a bare wire which trails up the chassis to hopefully, getting connected to a ground. Part two of the mystery is solved by viewing the photo, along with your specifying the definite presence of a substituted "resistor pair" being installed between 'Q7 pin 2 and 1-3-8 (grounded pins), in which case they would be replacing resistor R8, BUT that resultant value, instead, needs to be 10 megohms, not their currently achieved MUCH lower value, so pull them and replace with merely a small wattage 10 megohm resistor. That action alone should bring up the volume in that 1st audio stage ever a bit more. Now that " high " end of the volume control, as a currently unterminated connection, needs to get connected to "a" C37 capacitor, which I can assume to just be missing completely, possibly being left out by the last fix"OR". And then . . . AND THEN ! . . . that little puppy just might go out of its whimpering and whining attempts and go into full BARK mode for you. |
Now that Im understanding the pin numbers better, Im going through your messages again... Yellow wire from 2nd IF transformer to 'Q7 grid 1, sound dies completely.
Yellow wire (thru phono switch) goes thru C37 and into left terminal looking at the back of the volume control. And then the center terminal of volume thru capacitor to pin #2 on 6SQ7. So.. when I got your message I thought JACKPOT, we've GOT it.
Well we do and we don't. Here's what I get. Yellow wire into phono to C37 paper cap .005 then to volume control left terminal made no difference whatsoever. Then center terminal of volume thru cap to pin 2 on 6SQ7 and...
Remember a while ago I told you about that loud BUZZZZZZ I got when I touched a lead to that pin? Well now I have a VOLUME control for that buzzzzzz. When I touch the unit anywhere the buzzzz gets less, BUT the radio volume underneath it all remains the same.... although the volume control successfully changes the volume of the buzzzzz. So it would seem that we're on the right track but still the signal we're trying to push through that pin is bypassing that pin somewhere.
So in the background of the buzz, at a constant volume is a beautiful sounding radio. By simply disconnecting the cap from pin 2 of 6SQ7, the horrible buzzing goes away and I am left with a constant volume, beautifully playing radio.
It is possible that someone, somehow, sent the signal past 6SQ7 and it's going straight to 6V6? Is that feasible?
<10 minutes passes>
Okay I just went over to the bench and just out of desperation I removed the 6SQ7 and I got no sound (slight hummmm very slight).
So I took known good 6SQ7 and replaced "assumed" good 6SQ7 and lookie HERE...
Hopefully that link works.
So the volume potentiometer is old and has some dead spots and Im not concerned with that. My questions now are, when I turn it up towards the top of it's range and get that buzzzz that you can see goes away slightly when I touch anything on the chassis.. what is that?
Two thoughts:
(the paper cap Im using for C37 is OLD and is being replaced even though completely disconnecting that circuit has NO effect on sound coming from speaker)
AND
I haven't replaced the resistors yet (also ordered today)
And just out of curiosity, why is it that when I disconnect the wire to the terminal all the way to the left (high side) it has no effect at all? I thought that would kill it completely?
Still a little confused on how this all works, just when I think I've got an understanding, Im still scratching my head.
Im eternally grateful that you've gotten me this far, I've learned SO much... Im going to buy a video that I found on YouTube that traces the signal through the whole radio... Looks like a good investment unless you have another suggestion.
Again thank you so much. -Bob
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:
:Sir Bob . . . . . .Sssssssssssssss
:
:
:
:
:I am tacking this on, way down here, following your final / most current Date Time Group identification.
:
:
:After viewing all of your photos , it seems that you just need to take that capacitor that is curently connected to the center of the volume control ( and is your sets C25 capacitor) and disconnect its outer end and re route to connect to pin 2 of the 'Q7. That then gets the variable output of the volume control into the 1st grid of the
:'Q7.
:
:
:
:
:Now somewhere in the past photos I had found the the incorrect numerical designations to the "low" end and the "high " end of the volume control as per their assigned relationship that you had marked on the bit-piece schematic.
:
:((( Was photo #3 . . . aka . . ."volume control" JPG )))
:Now that might be that you possibly could have pulled that photo and replaced . . as I see several dupes . . and it seems that we have digressed . . . egresed . . or possibly transgressed . . as the case might be . . .into now having some parts recategorized as a full "trainwreck".
:
:
:
:
:Now the volume controls variable ROTOR should swing from the minimum to the maximum resistance of the volume control when you monitor, using an ohmmeters leads placed between it and the extreme ccw outer terminal lug on the control.
:
:
: (Visualize that mechanical rotors rotational action in your mind when rotating the shaft to its extreme CCW position and you will never get confused about which end of a volume control is which. . . . as per . . .its identification as to being the low end . . . grounded end.. . . of the control.)
:
:
:Overall . . . in that one pic . . .you had the "high" side and "low" side of the volume controls terminal lugs mis assigned . . . but the good thing was the proper assignment of the rotor !
:
:
:
:So I am seeing the "low" end, right teminal lug of the volume control going to a bare wire which trails up the chassis to hopefully, getting connected to a ground.
:
:
:
:Part two of the mystery is solved by viewing the photo, along with your specifying the definite presence of a substituted "resistor pair" being installed between 'Q7 pin 2 and 1-3-8 (grounded pins), in which case they would be replacing resistor R8, BUT that resultant value, instead, needs to be 10 megohms, not their currently achieved MUCH lower value, so pull them and replace with merely a small wattage 10 megohm resistor. That action alone should bring up the volume in that 1st audio stage ever a bit more.
:
:
:
:Now that " high " end of the volume control, as a currently unterminated connection, needs to get connected to "a" C37 capacitor, which I can assume to just be missing completely, possibly being left out by the last fix"OR".
:That caps other end then gets connected to the output lug of the pony-graf / ray-de-oh switch.
:
:
:
:And then . . . AND THEN ! . . . that little puppy just might go out of its whimpering and whining attempts and go into full BARK mode for you.
:
:
:Standing by . . .
:
:
:
:
:
:
:73's de Edd
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:Now that Im understanding the pin numbers better, Im going through your messages again... Yellow wire from 2nd IF transformer to 'Q7 grid 1, sound dies completely.
:Yellow wire from 2nd IF xformer to 6V6 grid 1, sound volume drops by approximately 1/2.
:
:As directed, .05 paper cap inline.
:
:
:
:
|
Good Evening! After I sent my last response, I took my J71 out of it's shell and took a good look at what was going on in there because it's DNA seems similar to the L640... And translated that into roughly what you sent me to do...
:
:Yellow wire (thru phono switch) goes thru C37 and into left terminal looking at the back of the volume control. And then the center terminal of volume thru capacitor to pin #2 on 6SQ7. So.. when I got your message I thought JACKPOT, we've GOT it.
:
:Well we do and we don't. Here's what I get. Yellow wire into phono to C37 paper cap .005 then to volume control left terminal made no difference whatsoever. Then center terminal of volume thru cap to pin 2 on 6SQ7 and...
:
:Remember a while ago I told you about that loud BUZZZZZZ I got when I touched a lead to that pin? Well now I have a VOLUME control for that buzzzzzz. When I touch the unit anywhere the buzzzz gets less, BUT the radio volume underneath it all remains the same.... although the volume control successfully changes the volume of the buzzzzz. So it would seem that we're on the right track but still the signal we're trying to push through that pin is bypassing that pin somewhere.
:
:So in the background of the buzz, at a constant volume is a beautiful sounding radio. By simply disconnecting the cap from pin 2 of 6SQ7, the horrible buzzing goes away and I am left with a constant volume, beautifully playing radio.
:
:It is possible that someone, somehow, sent the signal past 6SQ7 and it's going straight to 6V6? Is that feasible?
:
:<10 minutes passes>
:
:Okay I just went over to the bench and just out of desperation I removed the 6SQ7 and I got no sound (slight hummmm very slight).
:
:So I took known good 6SQ7 and replaced "assumed" good 6SQ7 and lookie HERE...
:
:CLICK HERE
:
:Hopefully that link works.
:
:So the volume potentiometer is old and has some dead spots and Im not concerned with that. My questions now are, when I turn it up towards the top of it's range and get that buzzzz that you can see goes away slightly when I touch anything on the chassis.. what is that?
:
:Two thoughts:
:(the paper cap Im using for C37 is OLD and is being replaced even though completely disconnecting that circuit has NO effect on sound coming from speaker)
:AND
:I haven't replaced the resistors yet (also ordered today)
:
:And just out of curiosity, why is it that when I disconnect the wire to the terminal all the way to the left (high side) it has no effect at all? I thought that would kill it completely?
:
:Still a little confused on how this all works, just when I think I've got an understanding, Im still scratching my head.
:
:Im eternally grateful that you've gotten me this far, I've learned SO much... Im going to buy a video that I found on YouTube that traces the signal through the whole radio... Looks like a good investment unless you have another suggestion.
:
:Again thank you so much. -Bob
:
:
:
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::
::
::
::
::
::
::
::
::
::
::
::
::Sir Bob . . . . . .Sssssssssssssss
::
::
::
::
::I am tacking this on, way down here, following your final / most current Date Time Group identification.
::
::
::After viewing all of your photos , it seems that you just need to take that capacitor that is curently connected to the center of the volume control ( and is your sets C25 capacitor) and disconnect its outer end and re route to connect to pin 2 of the 'Q7. That then gets the variable output of the volume control into the 1st grid of the
::'Q7.
::
::
::
::
::Now somewhere in the past photos I had found the the incorrect numerical designations to the "low" end and the "high " end of the volume control as per their assigned relationship that you had marked on the bit-piece schematic.
::
::((( Was photo #3 . . . aka . . ."volume control" JPG )))
::Now that might be that you possibly could have pulled that photo and replaced . . as I see several dupes . . and it seems that we have digressed . . . egresed . . or possibly transgressed . . as the case might be . . .into now having some parts recategorized as a full "trainwreck".
::
::
::
::
::Now the volume controls variable ROTOR should swing from the minimum to the maximum resistance of the volume control when you monitor, using an ohmmeters leads placed between it and the extreme ccw outer terminal lug on the control.
::
::
:: (Visualize that mechanical rotors rotational action in your mind when rotating the shaft to its extreme CCW position and you will never get confused about which end of a volume control is which. . . . as per . . .its identification as to being the low end . . . grounded end.. . . of the control.)
::
::
::Overall . . . in that one pic . . .you had the "high" side and "low" side of the volume controls terminal lugs mis assigned . . . but the good thing was the proper assignment of the rotor !
::
::
::
::So I am seeing the "low" end, right teminal lug of the volume control going to a bare wire which trails up the chassis to hopefully, getting connected to a ground.
::
::
::
::Part two of the mystery is solved by viewing the photo, along with your specifying the definite presence of a substituted "resistor pair" being installed between 'Q7 pin 2 and 1-3-8 (grounded pins), in which case they would be replacing resistor R8, BUT that resultant value, instead, needs to be 10 megohms, not their currently achieved MUCH lower value, so pull them and replace with merely a small wattage 10 megohm resistor. That action alone should bring up the volume in that 1st audio stage ever a bit more.
::
::
::
::Now that " high " end of the volume control, as a currently unterminated connection, needs to get connected to "a" C37 capacitor, which I can assume to just be missing completely, possibly being left out by the last fix"OR".
::That caps other end then gets connected to the output lug of the pony-graf / ray-de-oh switch.
::
::
::
::And then . . . AND THEN ! . . . that little puppy just might go out of its whimpering and whining attempts and go into full BARK mode for you.
::
::
::Standing by . . .
::
::
::
::
::
::
::73's de Edd
::
::
::
::
::
::
::
::
::
::
::
::
::
::Now that Im understanding the pin numbers better, Im going through your messages again... Yellow wire from 2nd IF transformer to 'Q7 grid 1, sound dies completely.
::Yellow wire from 2nd IF xformer to 6V6 grid 1, sound volume drops by approximately 1/2.
::
::As directed, .05 paper cap inline.
::
::
::
::
:
Well you were right on ALL counts. I have a nice bright flourescent light fixture in my garage, oh say about 3 feet from that makeshift test wire antenna... So I guess I was transmitting my OWN buzzzzzz from my radio station BUZZ AM in my garage. SO.... I tidied up the wiring by soldiering in my temporary paper cap, AND I made the resistors run in series instead of parallel. I plugged it in "the other way" too.
WOW. Nice clean sound on AM, albeit not very loud.
I also tried your other test and got BEAUTIFUL sound and much louder. So...
I'd say we're pretty much there!!! Once my new stuff comes in, I'll put in the 10M resistor and a new C37 that's not a paper cap.
Im not sure why the AM portion of the radio doesn't present full volume, but the DVD audio input had excellent volume and as you predicted the sound was absolutely amazing.
Just for kicks, I plugged my I-Pod in through the Aux/Phono jack with an RCA jack and it also plays beautifully.
With the aux temporarily soldiered in OR the I-Pod, you can run the volume all the way up to MAX and it gets louder and louder until the volume knob stops (and gets SUPER loud by the way...) On AM it goes from 0 to about 50% and back down to 0 by the time it's maxxxxed out.
Should I assume there's another resistor that's probably wrong in there somewhere? I think Im going to go through the schematic and see if I can identify each one and check to make sure the value is correct...
I've said it before but it's worth saying again, I really appreciate you sharing your knowledge with me.
-Bob
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:Sir Bob . . . . . . Ssss
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:Yellow wire (thru phono switch) goes thru C37 and into left terminal looking at the back of the volume control. And then the center terminal of volume thru capacitor to pin #2 on 6SQ7. So.. when I got your message I thought JACKPOT, we've GOT it.
:
:
:
:True, by all rights, that should have solved the problem with just those last few simple changes that you made.
:
:
:As it stands, in viewing your video and listening to its audio, it does seem that you DO have an inordinately high level of extraneous Buzzzzzzzz pick up, and probably by your having that large amount of loose naked wiring coming out from the chassis with test leads which IS subject to extraneous signal pick up.
:
:
:Now going by the audio of the video it is not AC line or filament /cathode inter leakage of a bad tube which would be 60~ hum. Now this really sounds like 120~ line hash as might be emitted by nearby flourescent lighting OR a high intensity light using an internal switch mode step down transformer instead of a conventional iron core transformer. OR any electronics or computer related equipment nearby using switch mode power supplies
: . . . but it really DOES, just sound like radiated flourescent light "hash" to me . . . that is being picked up.
:
:
:As the 6SQ7 circuitry now stands, you are presently having an, ~ 1.6 meg 1st grid circuitry impedance / matching by virtue of that pair of paralleled resistors that are now filling in for that function.
:
:
:Referring back to those two subbed in resistors values , and if you have not yet put in a 10 meg, you can merely lift some ends of the leads out and reconfigure them to being in SERIES arrangement so that you will then come up EXTWEEMLY close . . . as you need to be . . . to that desired 10 meg value. 8.2 + 2= 10.2 meg which will be just fine.
:
:
:The prior person may have very likely been attempting that, but was merely in error on his parallel /series perceptions.
:
:
:With that change you now have the have the input impedance ot the 6SQ7 grid circuitry set at that 10 meg value which is then accepting the max 2 meg and then downwards value of the volume control pot.
:
:
:As it is NOW, the 2 meg volume control dumps in its audio across the 1.6 meg and the volume then can increase up to THE point where the two values then equal, but then after that point the summed resistances decrease and the volume starts a slight diminishment of the volume that had just previously peaked . . . . thereby that squirrelly action of the volume control that you were experiencing . . . . and not expecting . . . as you progressively turned the volume shaft towards its upper range.
:
:
:
:
:
:Remember a while ago I told you about that loud BUZZZZZZ I got when I touched a lead to that pin? Well now I have a VOLUME control for that buzzzzzz. When I touch the unit anywhere the buzzzz gets less, BUT the radio volume underneath it all remains the same.... although the volume control successfully changes the volume of the buzzzzz. So it would seem that we're on the right track but still the signal we're trying to push through that pin is bypassing that pin somewhere.
:
:
:
:
:You remember when you either touched the chassis or the volume control shaft there was a difference in the amount of "hash". Well if you are now having the radio plugged into the raw AC line, try reversing the radios AC line cords plug 180 degrees to see possibly if that noise is less in one position, and if so, leave it plugged in at the quietest polarity.
:
:
:A battery powered transistor radio, tuned off station, volume up and starting at the problem spot might have the same hash on it and then you could move away from that spot to track down the offending source.
:
:
:( I still tend to believe it being the "loose" /"additional" test lead wiring connected and extending out from that 'Q7 1st grid connection, that is picking up the hash . . . or . . . how you clazy Amellicans say ? . . . . Buzzzzzz.)
:
:
:
:
:
:So in the background of the buzz, at a constant volume is a beautiful sounding radio. By simply disconnecting the cap from pin 2 of 6SQ7, the horrible buzzing goes away and I am left with a constant volume, beautifully playing radio.
:
:
:
:I will give you time to check out / confirm that info above.
:
:
:Preliminary info of :
:
:
:The next step . . . would be to commandeer your AC line powered CD or DVD player . . . or even an old Vee Cee RRRRuh would suffice, in order to have access to an RCA phono output connection of one of its audio channels.
:
:
:One then connects a single shielded patch cable from one of that selected units audio channel outputs to the close area of the volume control and lift the incoming connection to the high side of the sets volume control, but you can leave the insignifiant 100 pf mica HF bypass capacitor to ground.
:
:
:Solder tack on the center connector of the patch cable to the high end of the volume control. Solder tack on a short fill in bare jumper wire between the patch cables ground shell and the nearby low . . .grounded side of the volume control.
:
:
:Now if you have opted for a CD player along with a D-D-D quality of disc to play, you will have the very best sound quality that that old gal will EVER be able to produce for you.
:
:
:If you have perfectly flawless sound along with normal volume control action, along with no background buzzzzz then we need to look for contaminatoin of that incoming audio circuitry from the output of the second IF transformer of the radios detector circuitry output.
:
:
:( There possibly might be some hum related ground loop problem between interfacing those two AC powered devices together, if so, try the reversing of the plug of the Player device if no polarized plug is incorporated on it, but if so, then reverse the GE's power plug, 180 degrees.
:
:
:Thassssit . . . .
:
:
:
:
:
:73's de Edd
:
:
:
:
:
:
:
:
:
:
:
:Good Evening! After I sent my last response, I took my J71 out of it's shell and took a good look at what was going on in there because it's DNA seems similar to the L640... And translated that into roughly what you sent me to do...
::
::Yellow wire (thru phono switch) goes thru C37 and into left terminal looking at the back of the volume control. And then the center terminal of volume thru capacitor to pin #2 on 6SQ7. So.. when I got your message I thought JACKPOT, we've GOT it.
::
::Well we do and we don't. Here's what I get. Yellow wire into phono to C37 paper cap .005 then to volume control left terminal made no difference whatsoever. Then center terminal of volume thru cap to pin 2 on 6SQ7 and...
::
::Remember a while ago I told you about that loud BUZZZZZZ I got when I touched a lead to that pin? Well now I have a VOLUME control for that buzzzzzz. When I touch the unit anywhere the buzzzz gets less, BUT the radio volume underneath it all remains the same.... although the volume control successfully changes the volume of the buzzzzz. So it would seem that we're on the right track but still the signal we're trying to push through that pin is bypassing that pin somewhere.
::
::So in the background of the buzz, at a constant volume is a beautiful sounding radio. By simply disconnecting the cap from pin 2 of 6SQ7, the horrible buzzing goes away and I am left with a constant volume, beautifully playing radio.
::
::It is possible that someone, somehow, sent the signal past 6SQ7 and it's going straight to 6V6? Is that feasible?
::
::<10 minutes passes>
::
::Okay I just went over to the bench and just out of desperation I removed the 6SQ7 and I got no sound (slight hummmm very slight).
::
::So I took known good 6SQ7 and replaced "assumed" good 6SQ7 and lookie HERE...
::
::CLICK HERE
::
::Hopefully that link works.
::
::So the volume potentiometer is old and has some dead spots and Im not concerned with that. My questions now are, when I turn it up towards the top of it's range and get that buzzzz that you can see goes away slightly when I touch anything on the chassis.. what is that?
::
::Two thoughts:
::(the paper cap Im using for C37 is OLD and is being replaced even though completely disconnecting that circuit has NO effect on sound coming from speaker)
::AND
::I haven't replaced the resistors yet (also ordered today)
::
::And just out of curiosity, why is it that when I disconnect the wire to the terminal all the way to the left (high side) it has no effect at all? I thought that would kill it completely?
::
::Still a little confused on how this all works, just when I think I've got an understanding, Im still scratching my head.
::
::Im eternally grateful that you've gotten me this far, I've learned SO much... Im going to buy a video that I found on YouTube that traces the signal through the whole radio... Looks like a good investment unless you have another suggestion.
::
::Again thank you so much. -Bob
::
::
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:::
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:::
:::Sir Bob . . . . . .Sssssssssssssss
:::
:::
:::
:::
:::I am tacking this on, way down here, following your final / most current Date Time Group identification.
:::
:::
:::After viewing all of your photos , it seems that you just need to take that capacitor that is curently connected to the center of the volume control ( and is your sets C25 capacitor) and disconnect its outer end and re route to connect to pin 2 of the 'Q7. That then gets the variable output of the volume control into the 1st grid of the
:::'Q7.
:::
:::
:::
:::
:::Now somewhere in the past photos I had found the the incorrect numerical designations to the "low" end and the "high " end of the volume control as per their assigned relationship that you had marked on the bit-piece schematic.
:::
:::((( Was photo #3 . . . aka . . ."volume control" JPG )))
:::Now that might be that you possibly could have pulled that photo and replaced . . as I see several dupes . . and it seems that we have digressed . . . egresed . . or possibly transgressed . . as the case might be . . .into now having some parts recategorized as a full "trainwreck".
:::
:::
:::
:::
:::Now the volume controls variable ROTOR should swing from the minimum to the maximum resistance of the volume control when you monitor, using an ohmmeters leads placed between it and the extreme ccw outer terminal lug on the control.
:::
:::
::: (Visualize that mechanical rotors rotational action in your mind when rotating the shaft to its extreme CCW position and you will never get confused about which end of a volume control is which. . . . as per . . .its identification as to being the low end . . . grounded end.. . . of the control.)
:::
:::
:::Overall . . . in that one pic . . .you had the "high" side and "low" side of the volume controls terminal lugs mis assigned . . . but the good thing was the proper assignment of the rotor !
:::
:::
:::
:::So I am seeing the "low" end, right teminal lug of the volume control going to a bare wire which trails up the chassis to hopefully, getting connected to a ground.
:::
:::
:::
:::Part two of the mystery is solved by viewing the photo, along with your specifying the definite presence of a substituted "resistor pair" being installed between 'Q7 pin 2 and 1-3-8 (grounded pins), in which case they would be replacing resistor R8, BUT that resultant value, instead, needs to be 10 megohms, not their currently achieved MUCH lower value, so pull them and replace with merely a small wattage 10 megohm resistor. That action alone should bring up the volume in that 1st audio stage ever a bit more.
:::
:::
:::
:::Now that " high " end of the volume control, as a currently unterminated connection, needs to get connected to "a" C37 capacitor, which I can assume to just be missing completely, possibly being left out by the last fix"OR".
:::That caps other end then gets connected to the output lug of the pony-graf / ray-de-oh switch.
:::
:::
:::
:::And then . . . AND THEN ! . . . that little puppy just might go out of its whimpering and whining attempts and go into full BARK mode for you.
:::
:::
:::Standing by . . .
:::
:::
:::
:::
:::
:::
:::73's de Edd
:::
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:::
:::Now that Im understanding the pin numbers better, Im going through your messages again... Yellow wire from 2nd IF transformer to 'Q7 grid 1, sound dies completely.
:::Yellow wire from 2nd IF xformer to 6V6 grid 1, sound volume drops by approximately 1/2.
:::
:::As directed, .05 paper cap inline.
:::
:::
:::
:::
::
:
AND.. I apologize in advance for the music, it's the strongest signal I could find.. :)
:Hi Edd!
:
:Well you were right on ALL counts. I have a nice bright flourescent light fixture in my garage, oh say about 3 feet from that makeshift test wire antenna... So I guess I was transmitting my OWN buzzzzzz from my radio station BUZZ AM in my garage. SO.... I tidied up the wiring by soldiering in my temporary paper cap, AND I made the resistors run in series instead of parallel. I plugged it in "the other way" too.
:
:WOW. Nice clean sound on AM, albeit not very loud.
:
:I also tried your other test and got BEAUTIFUL sound and much louder. So...
:
:I'd say we're pretty much there!!! Once my new stuff comes in, I'll put in the 10M resistor and a new C37 that's not a paper cap.
:
:Im not sure why the AM portion of the radio doesn't present full volume, but the DVD audio input had excellent volume and as you predicted the sound was absolutely amazing.
:
:Just for kicks, I plugged my I-Pod in through the Aux/Phono jack with an RCA jack and it also plays beautifully.
:
:With the aux temporarily soldiered in OR the I-Pod, you can run the volume all the way up to MAX and it gets louder and louder until the volume knob stops (and gets SUPER loud by the way...) On AM it goes from 0 to about 50% and back down to 0 by the time it's maxxxxed out.
:
:CLICK HERE
:
:
:Should I assume there's another resistor that's probably wrong in there somewhere? I think Im going to go through the schematic and see if I can identify each one and check to make sure the value is correct...
:
:I've said it before but it's worth saying again, I really appreciate you sharing your knowledge with me.
:
:-Bob
:
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::Sir Bob . . . . . . Ssss
::
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::
::
::
::Yellow wire (thru phono switch) goes thru C37 and into left terminal looking at the back of the volume control. And then the center terminal of volume thru capacitor to pin #2 on 6SQ7. So.. when I got your message I thought JACKPOT, we've GOT it.
::
::
::
::True, by all rights, that should have solved the problem with just those last few simple changes that you made.
::
::
::As it stands, in viewing your video and listening to its audio, it does seem that you DO have an inordinately high level of extraneous Buzzzzzzzz pick up, and probably by your having that large amount of loose naked wiring coming out from the chassis with test leads which IS subject to extraneous signal pick up.
::
::
::Now going by the audio of the video it is not AC line or filament /cathode inter leakage of a bad tube which would be 60~ hum. Now this really sounds like 120~ line hash as might be emitted by nearby flourescent lighting OR a high intensity light using an internal switch mode step down transformer instead of a conventional iron core transformer. OR any electronics or computer related equipment nearby using switch mode power supplies
:: . . . but it really DOES, just sound like radiated flourescent light "hash" to me . . . that is being picked up.
::
::
::As the 6SQ7 circuitry now stands, you are presently having an, ~ 1.6 meg 1st grid circuitry impedance / matching by virtue of that pair of paralleled resistors that are now filling in for that function.
::
::
::Referring back to those two subbed in resistors values , and if you have not yet put in a 10 meg, you can merely lift some ends of the leads out and reconfigure them to being in SERIES arrangement so that you will then come up EXTWEEMLY close . . . as you need to be . . . to that desired 10 meg value. 8.2 + 2= 10.2 meg which will be just fine.
::
::
::The prior person may have very likely been attempting that, but was merely in error on his parallel /series perceptions.
::
::
::With that change you now have the have the input impedance ot the 6SQ7 grid circuitry set at that 10 meg value which is then accepting the max 2 meg and then downwards value of the volume control pot.
::
::
::As it is NOW, the 2 meg volume control dumps in its audio across the 1.6 meg and the volume then can increase up to THE point where the two values then equal, but then after that point the summed resistances decrease and the volume starts a slight diminishment of the volume that had just previously peaked . . . . thereby that squirrelly action of the volume control that you were experiencing . . . . and not expecting . . . as you progressively turned the volume shaft towards its upper range.
::
::
::
::
::
::Remember a while ago I told you about that loud BUZZZZZZ I got when I touched a lead to that pin? Well now I have a VOLUME control for that buzzzzzz. When I touch the unit anywhere the buzzzz gets less, BUT the radio volume underneath it all remains the same.... although the volume control successfully changes the volume of the buzzzzz. So it would seem that we're on the right track but still the signal we're trying to push through that pin is bypassing that pin somewhere.
::
::
::
::
::You remember when you either touched the chassis or the volume control shaft there was a difference in the amount of "hash". Well if you are now having the radio plugged into the raw AC line, try reversing the radios AC line cords plug 180 degrees to see possibly if that noise is less in one position, and if so, leave it plugged in at the quietest polarity.
::
::
::A battery powered transistor radio, tuned off station, volume up and starting at the problem spot might have the same hash on it and then you could move away from that spot to track down the offending source.
::
::
::( I still tend to believe it being the "loose" /"additional" test lead wiring connected and extending out from that 'Q7 1st grid connection, that is picking up the hash . . . or . . . how you clazy Amellicans say ? . . . . Buzzzzzz.)
::
::
::
::
::
::So in the background of the buzz, at a constant volume is a beautiful sounding radio. By simply disconnecting the cap from pin 2 of 6SQ7, the horrible buzzing goes away and I am left with a constant volume, beautifully playing radio.
::
::
::
::I will give you time to check out / confirm that info above.
::
::
::Preliminary info of :
::
::
::The next step . . . would be to commandeer your AC line powered CD or DVD player . . . or even an old Vee Cee RRRRuh would suffice, in order to have access to an RCA phono output connection of one of its audio channels.
::
::
::One then connects a single shielded patch cable from one of that selected units audio channel outputs to the close area of the volume control and lift the incoming connection to the high side of the sets volume control, but you can leave the insignifiant 100 pf mica HF bypass capacitor to ground.
::
::
::Solder tack on the center connector of the patch cable to the high end of the volume control. Solder tack on a short fill in bare jumper wire between the patch cables ground shell and the nearby low . . .grounded side of the volume control.
::
::
::Now if you have opted for a CD player along with a D-D-D quality of disc to play, you will have the very best sound quality that that old gal will EVER be able to produce for you.
::
::
::If you have perfectly flawless sound along with normal volume control action, along with no background buzzzzz then we need to look for contaminatoin of that incoming audio circuitry from the output of the second IF transformer of the radios detector circuitry output.
::
::
::( There possibly might be some hum related ground loop problem between interfacing those two AC powered devices together, if so, try the reversing of the plug of the Player device if no polarized plug is incorporated on it, but if so, then reverse the GE's power plug, 180 degrees.
::
::
::Thassssit . . . .
::
::
::
::
::
::73's de Edd
::
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::
::
::Good Evening! After I sent my last response, I took my J71 out of it's shell and took a good look at what was going on in there because it's DNA seems similar to the L640... And translated that into roughly what you sent me to do...
:::
:::Yellow wire (thru phono switch) goes thru C37 and into left terminal looking at the back of the volume control. And then the center terminal of volume thru capacitor to pin #2 on 6SQ7. So.. when I got your message I thought JACKPOT, we've GOT it.
:::
:::Well we do and we don't. Here's what I get. Yellow wire into phono to C37 paper cap .005 then to volume control left terminal made no difference whatsoever. Then center terminal of volume thru cap to pin 2 on 6SQ7 and...
:::
:::Remember a while ago I told you about that loud BUZZZZZZ I got when I touched a lead to that pin? Well now I have a VOLUME control for that buzzzzzz. When I touch the unit anywhere the buzzzz gets less, BUT the radio volume underneath it all remains the same.... although the volume control successfully changes the volume of the buzzzzz. So it would seem that we're on the right track but still the signal we're trying to push through that pin is bypassing that pin somewhere.
:::
:::So in the background of the buzz, at a constant volume is a beautiful sounding radio. By simply disconnecting the cap from pin 2 of 6SQ7, the horrible buzzing goes away and I am left with a constant volume, beautifully playing radio.
:::
:::It is possible that someone, somehow, sent the signal past 6SQ7 and it's going straight to 6V6? Is that feasible?
:::
:::<10 minutes passes>
:::
:::Okay I just went over to the bench and just out of desperation I removed the 6SQ7 and I got no sound (slight hummmm very slight).
:::
:::So I took known good 6SQ7 and replaced "assumed" good 6SQ7 and lookie HERE...
:::
:::CLICK HERE
:::
:::Hopefully that link works.
:::
:::So the volume potentiometer is old and has some dead spots and Im not concerned with that. My questions now are, when I turn it up towards the top of it's range and get that buzzzz that you can see goes away slightly when I touch anything on the chassis.. what is that?
:::
:::Two thoughts:
:::(the paper cap Im using for C37 is OLD and is being replaced even though completely disconnecting that circuit has NO effect on sound coming from speaker)
:::AND
:::I haven't replaced the resistors yet (also ordered today)
:::
:::And just out of curiosity, why is it that when I disconnect the wire to the terminal all the way to the left (high side) it has no effect at all? I thought that would kill it completely?
:::
:::Still a little confused on how this all works, just when I think I've got an understanding, Im still scratching my head.
:::
:::Im eternally grateful that you've gotten me this far, I've learned SO much... Im going to buy a video that I found on YouTube that traces the signal through the whole radio... Looks like a good investment unless you have another suggestion.
:::
:::Again thank you so much. -Bob
:::
:::
:::
::::
::::
::::
::::
::::
::::
::::
::::
::::
::::
::::
::::
::::
::::Sir Bob . . . . . .Sssssssssssssss
::::
::::
::::
::::
::::I am tacking this on, way down here, following your final / most current Date Time Group identification.
::::
::::
::::After viewing all of your photos , it seems that you just need to take that capacitor that is curently connected to the center of the volume control ( and is your sets C25 capacitor) and disconnect its outer end and re route to connect to pin 2 of the 'Q7. That then gets the variable output of the volume control into the 1st grid of the
::::'Q7.
::::
::::
::::
::::
::::Now somewhere in the past photos I had found the the incorrect numerical designations to the "low" end and the "high " end of the volume control as per their assigned relationship that you had marked on the bit-piece schematic.
::::
::::((( Was photo #3 . . . aka . . ."volume control" JPG )))
::::Now that might be that you possibly could have pulled that photo and replaced . . as I see several dupes . . and it seems that we have digressed . . . egresed . . or possibly transgressed . . as the case might be . . .into now having some parts recategorized as a full "trainwreck".
::::
::::
::::
::::
::::Now the volume controls variable ROTOR should swing from the minimum to the maximum resistance of the volume control when you monitor, using an ohmmeters leads placed between it and the extreme ccw outer terminal lug on the control.
::::
::::
:::: (Visualize that mechanical rotors rotational action in your mind when rotating the shaft to its extreme CCW position and you will never get confused about which end of a volume control is which. . . . as per . . .its identification as to being the low end . . . grounded end.. . . of the control.)
::::
::::
::::Overall . . . in that one pic . . .you had the "high" side and "low" side of the volume controls terminal lugs mis assigned . . . but the good thing was the proper assignment of the rotor !
::::
::::
::::
::::So I am seeing the "low" end, right teminal lug of the volume control going to a bare wire which trails up the chassis to hopefully, getting connected to a ground.
::::
::::
::::
::::Part two of the mystery is solved by viewing the photo, along with your specifying the definite presence of a substituted "resistor pair" being installed between 'Q7 pin 2 and 1-3-8 (grounded pins), in which case they would be replacing resistor R8, BUT that resultant value, instead, needs to be 10 megohms, not their currently achieved MUCH lower value, so pull them and replace with merely a small wattage 10 megohm resistor. That action alone should bring up the volume in that 1st audio stage ever a bit more.
::::
::::
::::
::::Now that " high " end of the volume control, as a currently unterminated connection, needs to get connected to "a" C37 capacitor, which I can assume to just be missing completely, possibly being left out by the last fix"OR".
::::That caps other end then gets connected to the output lug of the pony-graf / ray-de-oh switch.
::::
::::
::::
::::And then . . . AND THEN ! . . . that little puppy just might go out of its whimpering and whining attempts and go into full BARK mode for you.
::::
::::
::::Standing by . . .
::::
::::
::::
::::
::::
::::
::::73's de Edd
::::
::::
::::
::::
::::
::::
::::
::::
::::
::::
::::
::::
::::
::::Now that Im understanding the pin numbers better, Im going through your messages again... Yellow wire from 2nd IF transformer to 'Q7 grid 1, sound dies completely.
::::Yellow wire from 2nd IF xformer to 6V6 grid 1, sound volume drops by approximately 1/2.
::::
::::As directed, .05 paper cap inline.
::::
::::
::::
::::
:::
::
:
After close inspection, I believe resistor R3 is MISSING completely. Now I could be wrong but I can trace the yellow wire from the 2nd IF Transformer to the phono switch and up to volume with NO resistor in line (although I was able to locate EVERY other resistor R8,9,12,17,14 etc and they are all the correct value...)
Possibility for low AM volume?
"possibly the last "FIXOR" pulled all of the caps en masse and then overlooked putting that one in with all of the replacements."
-- You were definitely onto something...
Thanks! -Bob
:
:Im not sure why the AM portion of the radio doesn't present full volume, but the DVD audio input had excellent volume and as you predicted the sound was absolutely amazing.
:
On AM it goes from 0 to about 50% and back down to 0 by the time it's maxxxxed out.
:
:
:Should I assume there's another resistor that's probably wrong in there somewhere? I think Im going to go through the schematic and see if I can identify each one and check to make sure the value is correct...
:
In consulting the schema on that R3, do note that it is enclosed within the dotted lines of the shielding of the 2nd IF transformer . . . so that is indicative of its hidden physical placement also, along with that low value HF bypassing condenser of C17. |
FOLLOW UP
:
:After close inspection, I believe resistor R3 is MISSING completely. Now I could be wrong but I can trace the yellow wire from the 2nd IF Transformer to the phono switch and up to volume with NO resistor in line (although I was able to locate EVERY other resistor R8,9,12,17,14 etc and they are all the correct value...)
:
:Possibility for low AM volume?
:
:"possibly the last "FIXOR" pulled all of the caps en masse and then overlooked putting that one in with all of the replacements."
:
:-- You were definitely onto something...
:
:
:Thanks! -Bob
:
:
:
::
::Im not sure why the AM portion of the radio doesn't present full volume, but the DVD audio input had excellent volume and as you predicted the sound was absolutely amazing.
::
:On AM it goes from 0 to about 50% and back down to 0 by the time it's maxxxxed out.
::
::
::Should I assume there's another resistor that's probably wrong in there somewhere? I think Im going to go through the schematic and see if I can identify each one and check to make sure the value is correct...
::
:
:
I measured the resistance and you were right it was perfect. Then I noticed that in all of the testing and everything, that the yellow wire OUT of the 2nd IF transformer had become "un-soldiered" and was dangling EVER so close to where it should have been soldiered. Im pretty sure this happened by MY hand since I had done some work in that area.
As you probably already know, after I soldiered that puppy where it belongs... well here you go. One final result video.
SO... I really don't think the sound quality or volume could be any BETTER!!!
So my final question to you would be your suggestion for me to learn more about these circuits? The video I wanted to buy apparently is no longer available, so your suggestions are welcome.
Thanks again for all of your help, Edd. I really enjoyed the challenge and putting your knowledge to work and learning about these radios. Hopefully I absorbed some.
Thanks again! You're a genius. -Bob
:
:
:
:
:
:
:
:
:
:
:
:
:
:Sir Bob S. . . . . .
:
:
:
:In consulting the schema on that R3, do note that it is enclosed within the dotted lines of the shielding of the 2nd IF transformer . . . so that is indicative of its hidden physical placement also, along with that low value HF bypassing condenser of C17.
:
:
:So you just make measurement from the [BLACK] lead to the [YELLOW] lead and expect a reading of ~47k for that resistor plus the
:miniscule, added ~20 ohms of the IF secondary winding.
:
:
:I'm fully expecting for that combined reading to be O.K. . . . but at the same time, sort of hoping for it to be erred to VERY high resistance, as the list of possible probabilities is now getting progressively shorter.
:
:
:Reviewing:
:
:
:In the evaluation of the total AF output stages, from the high side of the volume control you found that the sound quality was superb, along with the achieved output level being more than adequate. And the one point of interest was that the volume control was making a progressive advancement of the volume from its quenched full CCW position, until it eventually was rotated to its full cw . . . max volume position.
:
:
:(Pee Ess . . no problem on the injected audio sourcing . . . since it was not RAP . . . nor . . . the fat lady screeching at the opera.)
:
:
:NOW shifting to the radio aspect of the testing, as best as I could perceive of the performance , by watching the shaft movement along with the adjunct sound output of the video / sound clip, am I correct that the radio sound does only seem to reach about its 50% equivalency of the prior Cee Dee's tests audio level ?
:
:
:BUTTTTT . . . does the audio also seem to hit its peak, somewhat PRIOR to max CW rotation and then seem to decline in volume before finally reaching that max CW positioning, and possibly appreciably attenuating before reaching max CW ?
:
:
:If so, I was expecting the new presence of the corrective 10.2 meg 'Q7 1st grid resistor pair to have taken care of THAT initial idiosyncrasy.
:
:
:Soooooo if you find no resistance fault with that mentioned - - - - IF transformer secondary down to the yellow wire loop - - - the same Cee Dee outputted audio needs to be re connected to the pins 4&5 of the 'Q7 and the audio shield is getting connected to the closest ground.
:Then the radio is tuned off from a station to a dead spot on the dial and you then see how the volume control now acts thru its full range.
:
:
:Standing by . . . with bated breath . . . .
:
:
:(And no . . . . that expression doesn't mean that you are holding worms or minners in your open mouth . . . but that you are, for extensive times, HOLDING your breath.)
:
:
:
:73's de Edd
:
:
:
:
:
:
:
:
:
:
:
:
:FOLLOW UP
::
::After close inspection, I believe resistor R3 is MISSING completely. Now I could be wrong but I can trace the yellow wire from the 2nd IF Transformer to the phono switch and up to volume with NO resistor in line (although I was able to locate EVERY other resistor R8,9,12,17,14 etc and they are all the correct value...)
::
::Possibility for low AM volume?
::
::"possibly the last "FIXOR" pulled all of the caps en masse and then overlooked putting that one in with all of the replacements."
::
::-- You were definitely onto something...
::
::
::Thanks! -Bob
::
::
::
:::
:::Im not sure why the AM portion of the radio doesn't present full volume, but the DVD audio input had excellent volume and as you predicted the sound was absolutely amazing.
:::
::On AM it goes from 0 to about 50% and back down to 0 by the time it's maxxxxed out.
:::
:::
:::Should I assume there's another resistor that's probably wrong in there somewhere? I think Im going to go through the schematic and see if I can identify each one and check to make sure the value is correct...
:::
::
::
: