Tube line up 7A7 - 7B8 - 6BA6 - 7E6 - 7AF7 - 7Y4 - 6V6 - 6V6.
:
:Tube line up 7A7 - 7B8 - 6BA6 - 7E6 - 7AF7 - 7Y4 - 6V6 - 6V6.
:
:Information I downloaded from radiomuseum says 7B8 or 6SA7 on schematic, Maybe because it also covers
the 8MF980 Radio.
It sounds like your problem is in the IF section. Do you have a signal generator?
All the Best,
Bill
::I have the Sams 42-12 Ford 8MF880 The schematic does not show a 6SA7. The only octal tubes are the pair of 6V6.
::
::Tube line up 7A7 - 7B8 - 6BA6 - 7E6 - 7AF7 - 7Y4 - 6V6 - 6V6.
::
::Information I downloaded from radiomuseum says 7B8 or 6SA7 on schematic, Maybe because it also covers
:the 8MF980 Radio.
:
:
:Hi Ralph,
: It sounds like your problem is in the IF section. Do you have a signal generator?
:
:All the Best,
:
:Bill
:::I have the Sams 42-12 Ford 8MF880 The schematic does not show a 6SA7. The only octal tubes are the pair of 6V6.
:::
:::Tube line up 7A7 - 7B8 - 6BA6 - 7E6 - 7AF7 - 7Y4 - 6V6 - 6V6.
:::
:::Information I downloaded from radiomuseum says 7B8 or 6SA7 on schematic, Maybe because it also covers
::the 8MF980 Radio.
::
::
:
:
:
::Hi Ralph,
:: It sounds like your problem is in the IF section. Do you have a signal generator?
::
::All the Best,
::
::Bill
::::I have the Sams 42-12 Ford 8MF880 The schematic does not show a 6SA7. The only octal tubes are the pair of 6V6.
::::
::::Tube line up 7A7 - 7B8 - 6BA6 - 7E6 - 7AF7 - 7Y4 - 6V6 - 6V6.
::::
::::Information I downloaded from radiomuseum says 7B8 or 6SA7 on schematic, Maybe because it also covers
:::the 8MF980 Radio.
:::
:::
::
::
:
:
I think I know what my problem is. It's a positive ground radio. I was treating it as negative ground.
Do you think I did any permanent damage?
::Hello, Yes I have a Signal-Marking Generator Model E-200-C from Precision Apparatus. Having difficulty aligning, still learning. Please help
::
:::Hi Ralph,
::: It sounds like your problem is in the IF section. Do you have a signal generator?
:::
:::All the Best,
:::
:::Bill
:::::I have the Sams 42-12 Ford 8MF880 The schematic does not show a 6SA7. The only octal tubes are the pair of 6V6.
:::::
:::::Tube line up 7A7 - 7B8 - 6BA6 - 7E6 - 7AF7 - 7Y4 - 6V6 - 6V6.
:::::
:::::Information I downloaded from radiomuseum says 7B8 or 6SA7 on schematic, Maybe because it also covers
::::the 8MF980 Radio.
::::
::::
:::
:::
::
::
:
:
:Car radios with a vibator don't care about polarity.
:
I removed one of the IF Transformer, about 62 ohms on each coil. Can the variable caps on the IF be bad? They are blackened. Can they be taken apart and cleaned?
:That good to know, Thanks . Now I'm getting Loud whistling at low end, nothing at the high end. With volume turned up
:
::Car radios with a vibator don't care about polarity.
::
:
:
That’s radios possibly of the right vintage to maybe have been using silver on the multiple leaves of the trimmer and may have been lightly silver plated /or/chemically flashed . . . particularly, if that black is appearing as a bold dark black.
Sir Ralph Cee. . . . .
Cleaning off with erasers light abrading action or use of a silver polish should confirm same.
73's de Edd
:Don’t know what the black stuff is. The trimmer capacitors can be taken apart and cleaned with a non-residue cleaner. You can use your signal generator as a signal injector. Test lead through a .01 capacitor and inject the 256 KC modulated signal to the primary side of the 2nd IF. If no signal comes through, inject signal to secondary diode detector side. If no signal still this print shows a 100 pf capacitor connected across each diode. Check that one. This print also shows a resistor and capacitor inside the 2nd IF. ( most likely 100pf ) Can be shorting to ground ?
:
Very sorry if I confused anyone. Can someone E-mail a copy of the schematics, the one I have is very hard to read. rc70@comcast.net
:
:
:
:
:
:
:
:
:
:
:
:
:
:
:Sir Ralph Cee. . . . .
:
:
:
:That’s radios possibly of the right vintage to maybe have been using silver on the multiple leaves of the trimmer and may have been lightly silver plated /or/chemically flashed . . . particularly, if that black is appearing as a bold dark black.
:
:
:Cleaning off with erasers light abrading action or use of a silver polish should confirm same.
:
:
:
:
:
:73's de Edd
:
:
:
:
:
:
:
:
:
::Don’t know what the black stuff is. The trimmer capacitors can be taken apart and cleaned with a non-residue cleaner. You can use your signal generator as a signal injector. Test lead through a .01 capacitor and inject the 256 KC modulated signal to the primary side of the 2nd IF. If no signal comes through, inject signal to secondary diode detector side. If no signal still this print shows a 100 pf capacitor connected across each diode. Check that one. This print also shows a resistor and capacitor inside the 2nd IF. ( most likely 100pf ) Can be shorting to ground ?
::
:
:
::I injected 262KC to the detector and all I can get is a popping at the speaker. If I touch or rub the detector I get a scatching sound. I double checked model# it's 8MF980 not the 8mf880 thats in the title.
:Very sorry if I confused anyone. Can someone E-mail a copy of the schematics, the one I have is very hard to read. rc70@comcast.net
:
:
::
::
::
::
::
::
::
::
::
::
::
::
::
::
::Sir Ralph Cee. . . . .
::
::
::
::That’s radios possibly of the right vintage to maybe have been using silver on the multiple leaves of the trimmer and may have been lightly silver plated /or/chemically flashed . . . particularly, if that black is appearing as a bold dark black.
::
::
::Cleaning off with erasers light abrading action or use of a silver polish should confirm same.
::
::
::
::
::
::73's de Edd
::
::
::
::
::
::
::
::
::
:::Don’t know what the black stuff is. The trimmer capacitors can be taken apart and cleaned with a non-residue cleaner. You can use your signal generator as a signal injector. Test lead through a .01 capacitor and inject the 256 KC modulated signal to the primary side of the 2nd IF. If no signal comes through, inject signal to secondary diode detector side. If no signal still this print shows a 100 pf capacitor connected across each diode. Check that one. This print also shows a resistor and capacitor inside the 2nd IF. ( most likely 100pf ) Can be shorting to ground ?
:::
::
::
:
:
O.K. lets initially see if I have the scenario . . . on my full re-reading . . . as to date . . . At our HIGH level of RF signal at the plate of the IF . . . I am saying its OK to use a commonly found /or/" borrowed " silicon diode such as a 1N4148 / 1N914 family from some other "newer" electronics you have around. 73's de Edd |
FORD / ZENITH 8MF980 SCHEMATIC:  |
:Don't have the schematic for that model, but the 8MF880 should be similar in operation. If you touch the center lug of the volume control, you should get a loud buzz. If not there is no AF coming from detector AF tube going to inverter then on to output tubes. ( assuming this set has a push pull output ) If you did get a buzz, and you injected a signal to the diode side from the IF secondary. Would think that the tube has a bad diode section. There are 3 tests on the tube tester. One for the triode and two for the diodes.
:
:
The tube in the converter socket is a 6SK7GT, schematic says tube is 6SA7. I can't get any noise with the home made converter and 265hz injected. I inject 400hz audio and I can here the tone at all points stated. With signal tracer I can here good rf from a station , at the RF tube and converter socket lug 8. I can barly hear a faint sound at lug 7 of IF tube. Nothing at any lead of both T1 and T2.
Center contact of volume control does make noise when touched.
:
:
:
:
:
:
:
:
:
:
:
:
:Sir Ralph Cee. . . . .
:
:
:
:O.K. lets initially see if I have the scenario . . . on my full re-reading . . . as to date . . .
:
:
:You are using your injecting 262 (265) Khz / 400 cycle AM tone modulated RF signal into the input of the 6SA7 mixer stage.
:
:
:( And that IS a 400~ AM modulated RF signal from that Paco 200 and NOT just a raw RF signal . )
:
:
:And you then confirm that it is passing thru the systems IF amp and on all the way to the 2nd IF plate where you seem to then have just lost it.
:
:
:Now, had that signal made it on thru the 6SR7 and the audio stages on past that . . . it should have been buzzing like a bee and really shaking up the sets speaker.
:
:
:
:The 100pf capacitor is reading at 42pf.
:
:
:
:This is NOT being THE problem.
:
:
:
:Can someone E-mail a copy of the schematics,, the one I have is very hard to read.
:
:
:
:Same situation here on my copies . . .BUT . . . I WILL enhance our specific " points of interest " on the schematic that I have prepared and placed waaaaaaaay down at the bottom for the following info submitted.
:
:
:I won't be out to the " mule barn " for a time . . . such that I could otherwise just pull out my stored / archived "Samuels " copy for this set.
:
:
:O.K. now lets consult the submitted marked up schematic and take note of the signal flow after its detection by the lower 6SR7's detector diode and the presence of the recovered audio at the bottom side of the secondary winding of T2 . .second IF transformer .
:
:
:It is isolated a bit by the presence of the pi section filter built within the IF can in the aspect of two 100 pf capacitors and their intermediary 33K resisitor placed between them.
:Sooooooo . . . . . . if you will now take an ohms reading from the top Green wire to the lower Brown one, it should read in in the order of ~ 33K, if so, all is fine in that transformers internal circuitry's aspect.
:
:
:Lets now see if we can take that 265 Khz signal that you have at the plate of the IF amp tube and look at my mark up and insertion of an off board detector circuit within my [ YELLOW ] Boxed drawing.
:
:
:It is consisting of a DC isolative .001 ufd RF coupling cap feeding into a detector diode and then on into its 220k load resistor and then the outflowing of the detected audio signal thru an .01 audio coupling capacitor.
:
:
:"Solder tack" the components of this circuit together very near the IF plate circuitry.
:The .001 RF cap gets connected to the plate of the IF tube and the .01 AF output capacitor gets connected to a short jumper clipped lead which is just long enough to reach to the most distant . . [A] . . signal injection point.
:
:
:Then the set is fired up and the modulated 400~ RF signal of 265 Khz is then coming in as before, but this time we have our outboared detector to feed its output into progressive audio stages in the chain.
:
:
:This . . [A] test point . . is the second stage of AF amplification and I am expecting your 400~ tone to be coming in, when the .01 AF output is connected to this [A ] point. . . or any where upon that GREEN marked up buss.
:
:
:If so . . . then great t t t t t (a la Tony the Tiger ) . . then you walk on back to [B] . . . . or anywhere along the BLUE buss.
:
:
:Then the injection points movement is to [C] and all along the AQUA buss.
:
:
:The final point is then to [D] or anywhere along the FUCSUIA buss, after making sure that the volume control is at its max volume position.
:
:
:The loudness of the received signal gens tone should have increased, for each step from our initial A test, on thru D.
:
:
:
:
:Techno Fill Ins:
:
:
:
:At our HIGH level of RF signal at the plate of the IF . . . I am saying its OK to use a commonly found /or/" borrowed " silicon diode such as a 1N4148 / 1N914 family from some other "newer" electronics you have around.
:
:
:No need to worry about hunting up a rarer germanium one . . . . I can even tolerate a "slow" " hi die capacitance " diode such as a common 1N400X generation of power diode . . just in case you are EXTWEMELY parts scarce.
:
:
:The YELLOW marked up electrolytic cathode bypass capacitor of the 6SR7 . . . was just to remind me to ask if you had replaced it ?
:
:
:Lets see what you find now, when injecting detected audio into the four signal paths of the AUDIO within the set, and then IF or Where you are loosing it ? ? ?
:
:
:
:
:
:
:73's de Edd
:
:
:
:
:
:
:
:
:
:
: FORD / ZENITH 8MF980 SCHEMATIC:
:
:
:
:
:
:
:
:
:
:
:
:
:
::Don't have the schematic for that model, but the 8MF880 should be similar in operation. If you touch the center lug of the volume control, you should get a loud buzz. If not there is no AF coming from detector AF tube going to inverter then on to output tubes. ( assuming this set has a push pull output ) If you did get a buzz, and you injected a signal to the diode side from the IF secondary. Would think that the tube has a bad diode section. There are 3 tests on the tube tester. One for the triode and two for the diodes.
::
::
:
:
|
::I'm sorry for the slow reply, but thankyou very much for your time and effort in helping with my project.
:The tube in the converter socket is a 6SK7GT, schematic says tube is 6SA7. I can't get any noise with the home made converter and 265hz injected. I inject 400hz audio and I can here the tone at all points stated. With signal tracer I can here good rf from a station , at the RF tube and converter socket lug 8. I can barly hear a faint sound at lug 7 of IF tube. Nothing at any lead of both T1 and T2.
:Center contact of volume control does make noise when touched.
:
:
:
:
::
::
::
::
::
::
::
::
::
::
::
::
::Sir Ralph Cee. . . . .
::
::
::
::O.K. lets initially see if I have the scenario . . . on my full re-reading . . . as to date . . .
::
::
::You are using your injecting 262 (265) Khz / 400 cycle AM tone modulated RF signal into the input of the 6SA7 mixer stage.
::
::
::( And that IS a 400~ AM modulated RF signal from that Paco 200 and NOT just a raw RF signal . )
::
::
::And you then confirm that it is passing thru the systems IF amp and on all the way to the 2nd IF plate where you seem to then have just lost it.
::
::
::Now, had that signal made it on thru the 6SR7 and the audio stages on past that . . . it should have been buzzing like a bee and really shaking up the sets speaker.
::
::
::
::The 100pf capacitor is reading at 42pf.
::
::
::
::This is NOT being THE problem.
::
::
::
::Can someone E-mail a copy of the schematics,, the one I have is very hard to read.
::
::
::
::Same situation here on my copies . . .BUT . . . I WILL enhance our specific " points of interest " on the schematic that I have prepared and placed waaaaaaaay down at the bottom for the following info submitted.
::
::
::I won't be out to the " mule barn " for a time . . . such that I could otherwise just pull out my stored / archived "Samuels " copy for this set.
::
::
::O.K. now lets consult the submitted marked up schematic and take note of the signal flow after its detection by the lower 6SR7's detector diode and the presence of the recovered audio at the bottom side of the secondary winding of T2 . .second IF transformer .
::
::
::It is isolated a bit by the presence of the pi section filter built within the IF can in the aspect of two 100 pf capacitors and their intermediary 33K resisitor placed between them.
::Sooooooo . . . . . . if you will now take an ohms reading from the top Green wire to the lower Brown one, it should read in in the order of ~ 33K, if so, all is fine in that transformers internal circuitry's aspect.
::
::
::Lets now see if we can take that 265 Khz signal that you have at the plate of the IF amp tube and look at my mark up and insertion of an off board detector circuit within my [ YELLOW ] Boxed drawing.
::
::
::It is consisting of a DC isolative .001 ufd RF coupling cap feeding into a detector diode and then on into its 220k load resistor and then the outflowing of the detected audio signal thru an .01 audio coupling capacitor.
::
::
::"Solder tack" the components of this circuit together very near the IF plate circuitry.
::The .001 RF cap gets connected to the plate of the IF tube and the .01 AF output capacitor gets connected to a short jumper clipped lead which is just long enough to reach to the most distant . . [A] . . signal injection point.
::
::
::Then the set is fired up and the modulated 400~ RF signal of 265 Khz is then coming in as before, but this time we have our outboared detector to feed its output into progressive audio stages in the chain.
::
::
::This . . [A] test point . . is the second stage of AF amplification and I am expecting your 400~ tone to be coming in, when the .01 AF output is connected to this [A ] point. . . or any where upon that GREEN marked up buss.
::
::
::If so . . . then great t t t t t (a la Tony the Tiger ) . . then you walk on back to [B] . . . . or anywhere along the BLUE buss.
::
::
::Then the injection points movement is to [C] and all along the AQUA buss.
::
::
::The final point is then to [D] or anywhere along the FUCSUIA buss, after making sure that the volume control is at its max volume position.
::
::
::The loudness of the received signal gens tone should have increased, for each step from our initial A test, on thru D.
::
::
::
::
::Techno Fill Ins:
::
::
::
::At our HIGH level of RF signal at the plate of the IF . . . I am saying its OK to use a commonly found /or/" borrowed " silicon diode such as a 1N4148 / 1N914 family from some other "newer" electronics you have around.
::
::
::No need to worry about hunting up a rarer germanium one . . . . I can even tolerate a "slow" " hi die capacitance " diode such as a common 1N400X generation of power diode . . just in case you are EXTWEMELY parts scarce.
::
::
::The YELLOW marked up electrolytic cathode bypass capacitor of the 6SR7 . . . was just to remind me to ask if you had replaced it ?
::
::
::Lets see what you find now, when injecting detected audio into the four signal paths of the AUDIO within the set, and then IF or Where you are loosing it ? ? ?
::
::
::
::
::
::
::73's de Edd
::
::
::
::
::
::
::
::
::
::
:: FORD / ZENITH 8MF980 SCHEMATIC:
::
::
::
::
::
::
::
::
::
::
::
::
::
:::Don't have the schematic for that model, but the 8MF880 should be similar in operation. If you touch the center lug of the volume control, you should get a loud buzz. If not there is no AF coming from detector AF tube going to inverter then on to output tubes. ( assuming this set has a push pull output ) If you did get a buzz, and you injected a signal to the diode side from the IF secondary. Would think that the tube has a bad diode section. There are 3 tests on the tube tester. One for the triode and two for the diodes.
:::
:::
::
::
:
:
the 6SK7. That solved the problem. Prior to this I replaced the electrolytics and all the paper capacitors. I also pulled and cleaned both IF Transformer variable caps. The only problem I have is aligning. I did it by ear and get about 7 station.
Alot of static when I change station. Is there a way
to eliminate the static. Thanks again to Edd, Warren and everyone that help me figure this out.
:
:
:
:
:
:
:
:
:
:
:
:
:
:Sir Ralph Cee. . . . .
:
:
:Well then . . . looks like you need to get a 6SA7 for the mixer tube slot, as that presently used 6SK7 in that position, is incapable of doing the mixers local oscillator function.
:
:
:
:With signal tracer I can here good rf from a station , at the RF tube and converter socket lug 8. I can barly hear a faint sound at lug 7 of IF tube. Nothing at any lead of both T1 and T2
:
:
:
:
:Confirmed . . .by using your signal tracer . . . It is certainly logical to be able to tune the radio tuning onto a stronger station and be able to monitor it at the 1 st grid of the 6BA6 RF amp, at its plate and then also at the grid of the "mixer" and even at its plate, but with no local oscillator action from that present "6SK7" ersatz " mixer " tube, you are not going to even develop a required 265 difference IF signal to pass into the IF stages.
:
:
:
:
:
:
:
:
:
:73's de Edd
:
:
:
:
:
:
:
:
:
:
:::I'm sorry for the slow reply, but thankyou very much for your time and effort in helping with my project.
::The tube in the converter socket is a 6SK7GT, schematic says tube is 6SA7. I can't get any noise with the home made converter and 265hz injected. I inject 400hz audio and I can here the tone at all points stated. With signal tracer I can here good rf from a station , at the RF tube and converter socket lug 8. I can barly hear a faint sound at lug 7 of IF tube. Nothing at any lead of both T1 and T2.
::Center contact of volume control does make noise when touched.
::
::
::
::
:::
:::
:::
:::
:::
:::
:::
:::
:::
:::
:::
:::
:::Sir Ralph Cee. . . . .
:::
:::
:::
:::O.K. lets initially see if I have the scenario . . . on my full re-reading . . . as to date . . .
:::
:::
:::You are using your injecting 262 (265) Khz / 400 cycle AM tone modulated RF signal into the input of the 6SA7 mixer stage.
:::
:::
:::( And that IS a 400~ AM modulated RF signal from that Paco 200 and NOT just a raw RF signal . )
:::
:::
:::And you then confirm that it is passing thru the systems IF amp and on all the way to the 2nd IF plate where you seem to then have just lost it.
:::
:::
:::Now, had that signal made it on thru the 6SR7 and the audio stages on past that . . . it should have been buzzing like a bee and really shaking up the sets speaker.
:::
:::
:::
:::The 100pf capacitor is reading at 42pf.
:::
:::
:::
:::This is NOT being THE problem.
:::
:::
:::
:::Can someone E-mail a copy of the schematics,, the one I have is very hard to read.
:::
:::
:::
:::Same situation here on my copies . . .BUT . . . I WILL enhance our specific " points of interest " on the schematic that I have prepared and placed waaaaaaaay down at the bottom for the following info submitted.
:::
:::
:::I won't be out to the " mule barn " for a time . . . such that I could otherwise just pull out my stored / archived "Samuels " copy for this set.
:::
:::
:::O.K. now lets consult the submitted marked up schematic and take note of the signal flow after its detection by the lower 6SR7's detector diode and the presence of the recovered audio at the bottom side of the secondary winding of T2 . .second IF transformer .
:::
:::
:::It is isolated a bit by the presence of the pi section filter built within the IF can in the aspect of two 100 pf capacitors and their intermediary 33K resisitor placed between them.
:::Sooooooo . . . . . . if you will now take an ohms reading from the top Green wire to the lower Brown one, it should read in in the order of ~ 33K, if so, all is fine in that transformers internal circuitry's aspect.
:::
:::
:::Lets now see if we can take that 265 Khz signal that you have at the plate of the IF amp tube and look at my mark up and insertion of an off board detector circuit within my [ YELLOW ] Boxed drawing.
:::
:::
:::It is consisting of a DC isolative .001 ufd RF coupling cap feeding into a detector diode and then on into its 220k load resistor and then the outflowing of the detected audio signal thru an .01 audio coupling capacitor.
:::
:::
:::"Solder tack" the components of this circuit together very near the IF plate circuitry.
:::The .001 RF cap gets connected to the plate of the IF tube and the .01 AF output capacitor gets connected to a short jumper clipped lead which is just long enough to reach to the most distant . . [A] . . signal injection point.
:::
:::
:::Then the set is fired up and the modulated 400~ RF signal of 265 Khz is then coming in as before, but this time we have our outboared detector to feed its output into progressive audio stages in the chain.
:::
:::
:::This . . [A] test point . . is the second stage of AF amplification and I am expecting your 400~ tone to be coming in, when the .01 AF output is connected to this [A ] point. . . or any where upon that GREEN marked up buss.
:::
:::
:::If so . . . then great t t t t t (a la Tony the Tiger ) . . then you walk on back to [B] . . . . or anywhere along the BLUE buss.
:::
:::
:::Then the injection points movement is to [C] and all along the AQUA buss.
:::
:::
:::The final point is then to [D] or anywhere along the FUCSUIA buss, after making sure that the volume control is at its max volume position.
:::
:::
:::The loudness of the received signal gens tone should have increased, for each step from our initial A test, on thru D.
:::
:::
:::
:::
:::Techno Fill Ins:
:::
:::
:::
:::At our HIGH level of RF signal at the plate of the IF . . . I am saying its OK to use a commonly found /or/" borrowed " silicon diode such as a 1N4148 / 1N914 family from some other "newer" electronics you have around.
:::
:::
:::No need to worry about hunting up a rarer germanium one . . . . I can even tolerate a "slow" " hi die capacitance " diode such as a common 1N400X generation of power diode . . just in case you are EXTWEMELY parts scarce.
:::
:::
:::The YELLOW marked up electrolytic cathode bypass capacitor of the 6SR7 . . . was just to remind me to ask if you had replaced it ?
:::
:::
:::Lets see what you find now, when injecting detected audio into the four signal paths of the AUDIO within the set, and then IF or Where you are loosing it ? ? ?
:::
:::
:::
:::
:::
:::
:::73's de Edd
:::
:::
:::
:::
:::
:::
:::
:::
:::
:::
::: FORD / ZENITH 8MF980 SCHEMATIC:
:::
:::
:::
:::
:::
:::
:::
:::
:::
:::
:::
:::
:::
::::Don't have the schematic for that model, but the 8MF880 should be similar in operation. If you touch the center lug of the volume control, you should get a loud buzz. If not there is no AF coming from detector AF tube going to inverter then on to output tubes. ( assuming this set has a push pull output ) If you did get a buzz, and you injected a signal to the diode side from the IF secondary. Would think that the tube has a bad diode section. There are 3 tests on the tube tester. One for the triode and two for the diodes.
::::
::::
:::
:::
::
::
:
: