Where can I find a free schematic that is readable. My copy from Tech Preservation is very small and wo/pl. Running on AC line, the highest filament measurement is 1.2vdc, and the A+ max is 6.5vdc at pin 7 of the 3V4. On EDD's recommendations, built a batt pack with 10 9 volters and 6 "AA" cells per his posting 3/24/08. All voltages seem 15%-20% low, if I'm reading ??? the numbers correctly. This my 1st AC/DC set, so I'll solve the isolation transformer problem w/2ea 12.6vac Rad Shak parts wired back to back. Radio hums, and worked poorly at first, but now just hum. 1R5 converter measured weak on my tester, so suspect converter inoperable.
marv
Are the low voltages with battery supply or with AC operation? Low voltage can cause the oscillator to poop out.
With two little 12-V xfmrs back to back, you will get less voltage out than in.
Also, this set has a selenium rectifier. That might have crept up in voltage drop for the AC supply. You probably should replace it with a silicon 1N400x diode, but you'll have to add some additional resistance in series with R13 to keep the volages from being too high during AC operation.
Doug
:Forum,
:Where can I find a free schematic that is readable. My copy from Tech Preservation is very small and wo/pl. Running on AC line, the highest filament measurement is 1.2vdc, and the A+ max is 6.5vdc at pin 7 of the 3V4. On EDD's recommendations, built a batt pack with 10 9 volters and 6 "AA" cells per his posting 3/24/08. All voltages seem 15%-20% low, if I'm reading ??? the numbers correctly. This my 1st AC/DC set, so I'll solve the isolation transformer problem w/2ea 12.6vac Rad Shak parts wired back to back. Radio hums, and worked poorly at first, but now just hum. 1R5 converter measured weak on my tester, so suspect converter inoperable.
:
:marv
marv
:Marv - Can't help with another schematic. But when I open it in DjVu, I can zoom the size, and it seems pretty readable on my computer screen.
:
:Are the low voltages with battery supply or with AC operation? Low voltage can cause the oscillator to poop out.
:
:With two little 12-V xfmrs back to back, you will get less voltage out than in.
:
:Also, this set has a selenium rectifier. That might have crept up in voltage drop for the AC supply. You probably should replace it with a silicon 1N400x diode, but you'll have to add some additional resistance in series with R13 to keep the volages from being too high during AC operation.
:Doug
:
::Forum,
::Where can I find a free schematic that is readable. My copy from Tech Preservation is very small and wo/pl. Running on AC line, the highest filament measurement is 1.2vdc, and the A+ max is 6.5vdc at pin 7 of the 3V4. On EDD's recommendations, built a batt pack with 10 9 volters and 6 "AA" cells per his posting 3/24/08. All voltages seem 15%-20% low, if I'm reading ??? the numbers correctly. This my 1st AC/DC set, so I'll solve the isolation transformer problem w/2ea 12.6vac Rad Shak parts wired back to back. Radio hums, and worked poorly at first, but now just hum. 1R5 converter measured weak on my tester, so suspect converter inoperable.
::
::marv
Your series resistor is on the DC, right? The diode will put out about 165V peak ripple without a cap or load. But with the power supply cap and a load, it will put out less.
Maybe try, say, a 200-ohm series resistor and see what it gives you, DC voltage wise, at the cap and with the radio's usual B+ load.
I'm not sure how you are computing the required resistor wattage. Use V^2/R, and double it for safety. You can just measure the voltage drop across the resistor when you get the voltage to the cap that you are looking for.
Doug
:OK!! Here is my problem for replacing the faulty selenium rectifier with a 1N4007. Using 165VPP reference, I calculated a series resistor of 397 ohms/6W to arrive with 100VDC at C1A. Conversley, using 117VRMS, calculated a series resistor of 17 ohms-1/2 W to arrive with 100VDC at C1A. Where is my error.
:
:marv
I'll answer both your posts here. Opted to put the "R" on the AC side of the diode, and did end up using the 1N4007 that MAG sent me. The 8A parts were a big case with hole, making heatsinking easy, but needed a spot for the resistor too, so made a small pcb. Breadboarded outboard with spare components, and ended up with a 56 ohm 2W resistor. Had 111VDC at simulated C1A; 74.2VDC at simulated C1B and 8.1VDC at the filament string, almost "spot on" Installed in radio have 105VDC at C1A; 69.7VDC at C1B and 8.1VDC at the filament string. Sam's docs quotes +/- 15% for all voltages, so guess I'm fine. Radio works fine AC or DC, even with the weak 1R5, but did replace it. I'llput it all back in the case tonite. Have to redesign my velcro latch on the batt pack door too. Its a little weak, and sometimes opens just enough to lose batt contact. I've built 4 different versions, all of which have small shortcomings, but the one I'll sell to customer is the smallest, and fits well into the space alloted by Zenith.
marv
:Marv: Now I'm confused.
:
:Your series resistor is on the DC, right? The diode will put out about 165V peak ripple without a cap or load. But with the power supply cap and a load, it will put out less.
:
:Maybe try, say, a 200-ohm series resistor and see what it gives you, DC voltage wise, at the cap and with the radio's usual B+ load.
:
:I'm not sure how you are computing the required resistor wattage. Use V^2/R, and double it for safety. You can just measure the voltage drop across the resistor when you get the voltage to the cap that you are looking for.
:Doug
:
::OK!! Here is my problem for replacing the faulty selenium rectifier with a 1N4007. Using 165VPP reference, I calculated a series resistor of 397 ohms/6W to arrive with 100VDC at C1A. Conversley, using 117VRMS, calculated a series resistor of 17 ohms-1/2 W to arrive with 100VDC at C1A. Where is my error.
::
::marv
:
The next battery portable I come across, I'll send to you for repair!
:Doug,
:I'll answer both your posts here. Opted to put the "R" on the AC side of the diode, and did end up using the 1N4007 that MAG sent me. The 8A parts were a big case with hole, making heatsinking easy, but needed a spot for the resistor too, so made a small pcb. Breadboarded outboard with spare components, and ended up with a 56 ohm 2W resistor. Had 111VDC at simulated C1A; 74.2VDC at simulated C1B and 8.1VDC at the filament string, almost "spot on" Installed in radio have 105VDC at C1A; 69.7VDC at C1B and 8.1VDC at the filament string. Sam's docs quotes +/- 15% for all voltages, so guess I'm fine. Radio works fine AC or DC, even with the weak 1R5, but did replace it. I'llput it all back in the case tonite. Have to redesign my velcro latch on the batt pack door too. Its a little weak, and sometimes opens just enough to lose batt contact. I've built 4 different versions, all of which have small shortcomings, but the one I'll sell to customer is the smallest, and fits well into the space alloted by Zenith.
:
:marv
:
::Marv: Now I'm confused.
::
::Your series resistor is on the DC, right? The diode will put out about 165V peak ripple without a cap or load. But with the power supply cap and a load, it will put out less.
::
::Maybe try, say, a 200-ohm series resistor and see what it gives you, DC voltage wise, at the cap and with the radio's usual B+ load.
::
::I'm not sure how you are computing the required resistor wattage. Use V^2/R, and double it for safety. You can just measure the voltage drop across the resistor when you get the voltage to the cap that you are looking for.
::Doug
::
This may not be answered easily, and knowing the wide variation in AC/DC sets, what could one expect in the way of reasonably good play time from the alkaline 9V/AA pack in this radio? As I recall the discharge curve(s) are nearly equal, but of course no radio will work down to the "0" volts. What is the best guess/calc (25%,50%,75% of remaining charge) that would predict the lowest voltage needed for this set to play?
marv
:Marv: OK, things sound great. I wouldn't have worried about that "weak" 1R5 - it either works or it doesn't. But you replaced, so OK.
:
:The next battery portable I come across, I'll send to you for repair!
:
::Doug,
::I'll answer both your posts here. Opted to put the "R" on the AC side of the diode, and did end up using the 1N4007 that MAG sent me. The 8A parts were a big case with hole, making heatsinking easy, but needed a spot for the resistor too, so made a small pcb. Breadboarded outboard with spare components, and ended up with a 56 ohm 2W resistor. Had 111VDC at simulated C1A; 74.2VDC at simulated C1B and 8.1VDC at the filament string, almost "spot on" Installed in radio have 105VDC at C1A; 69.7VDC at C1B and 8.1VDC at the filament string. Sam's docs quotes +/- 15% for all voltages, so guess I'm fine. Radio works fine AC or DC, even with the weak 1R5, but did replace it. I'llput it all back in the case tonite. Have to redesign my velcro latch on the batt pack door too. Its a little weak, and sometimes opens just enough to lose batt contact. I've built 4 different versions, all of which have small shortcomings, but the one I'll sell to customer is the smallest, and fits well into the space alloted by Zenith.
::
::marv
::
:::Marv: Now I'm confused.
:::
:::Your series resistor is on the DC, right? The diode will put out about 165V peak ripple without a cap or load. But with the power supply cap and a load, it will put out less.
:::
:::Maybe try, say, a 200-ohm series resistor and see what it gives you, DC voltage wise, at the cap and with the radio's usual B+ load.
:::
:::I'm not sure how you are computing the required resistor wattage. Use V^2/R, and double it for safety. You can just measure the voltage drop across the resistor when you get the voltage to the cap that you are looking for.
:::Doug
:::
:
Zenith 5L41 is in Sams 224-18. According to the Sams, filament voltages should be 1.4 VDC, and there shou0ld be 8.3 VDC on pin 7 of the 3V4. B+ on the 1R5 plate should be about 100 VDC. All voltages are measured from the negative end of the filter capacitors, not the chassis. If all voltages are low, suspect the selenium rectifier or the resistor string following the rectifier. Low volatge may keep a marginal oscillator from working.
I can drop a copy of the Sams in the mail if you like.
Meade
*************************************************
:Forum,
:Where can I find a free schematic that is readable. My copy from Tech Preservation is very small and wo/pl. Running on AC line, the highest filament measurement is 1.2vdc, and the A+ max is 6.5vdc at pin 7 of the 3V4. On EDD's recommendations, built a batt pack with 10 9 volters and 6 "AA" cells per his posting 3/24/08. All voltages seem 15%-20% low, if I'm reading ??? the numbers correctly. This my 1st AC/DC set, so I'll solve the isolation transformer problem w/2ea 12.6vac Rad Shak parts wired back to back. Radio hums, and worked poorly at first, but now just hum. 1R5 converter measured weak on my tester, so suspect converter inoperable.
:
:marv
Yes, please do mail it, and once again you've pulled me out of the fire. Thanks Meade. My eyeballs are sore from looking at the schem, and trying to decide the voltages. With all tubes in etc, getting 100VDC at the rectifier out. The Rad Shak 12.6 VAC xformer is a 3.5A version, the strongest they have, and I'll pick up some 1N4003's or 1N4004's Can't remember the PIV of either. Finished the Mopar 802 last week, and demo'd it, but not in the car for customer final test/gripes.
marv
:Hi Marv,
:
:Zenith 5L41 is in Sams 224-18. According to the Sams, filament voltages should be 1.4 VDC, and there shou0ld be 8.3 VDC on pin 7 of the 3V4. B+ on the 1R5 plate should be about 100 VDC. All voltages are measured from the negative end of the filter capacitors, not the chassis. If all voltages are low, suspect the selenium rectifier or the resistor string following the rectifier. Low volatge may keep a marginal oscillator from working.
:
:I can drop a copy of the Sams in the mail if you like.
:
:Meade
:
:
:*************************************************
:
::Forum,
::Where can I find a free schematic that is readable. My copy from Tech Preservation is very small and wo/pl. Running on AC line, the highest filament measurement is 1.2vdc, and the A+ max is 6.5vdc at pin 7 of the 3V4. On EDD's recommendations, built a batt pack with 10 9 volters and 6 "AA" cells per his posting 3/24/08. All voltages seem 15%-20% low, if I'm reading ??? the numbers correctly. This my 1st AC/DC set, so I'll solve the isolation transformer problem w/2ea 12.6vac Rad Shak parts wired back to back. Radio hums, and worked poorly at first, but now just hum. 1R5 converter measured weak on my tester, so suspect converter inoperable.
::
::marv
But my bet is the selenium rectifier is dropping too much voltage. But if your voltages are also low with battery input, then I'm a little stumped.
In my first response, I mistakenly referred to R13. I should have said R15.
Doug
:The Rad Shak 12.6 VAC xformer is a 3.5A version, the strongest they have.
:
:marv
:
::Hi Marv,
::
::Zenith 5L41 is in Sams 224-18. According to the Sams, filament voltages should be 1.4 VDC, and there shou0ld be 8.3 VDC on pin 7 of the 3V4. B+ on the 1R5 plate should be about 100 VDC. All voltages are measured from the negative end of the filter capacitors, not the chassis. If all voltages are low, suspect the selenium rectifier or the resistor string following the rectifier. Low volatge may keep a marginal oscillator from working.
::
::I can drop a copy of the Sams in the mail if you like.
::
::Meade
::
::
::*************************************************
::
:::Forum,
:::Where can I find a free schematic that is readable. My copy from Tech Preservation is very small and wo/pl. Running on AC line, the highest filament measurement is 1.2vdc, and the A+ max is 6.5vdc at pin 7 of the 3V4. On EDD's recommendations, built a batt pack with 10 9 volters and 6 "AA" cells per his posting 3/24/08. All voltages seem 15%-20% low, if I'm reading ??? the numbers correctly. This my 1st AC/DC set, so I'll solve the isolation transformer problem w/2ea 12.6vac Rad Shak parts wired back to back. Radio hums, and worked poorly at first, but now just hum. 1R5 converter measured weak on my tester, so suspect converter inoperable.
:::
:::marv
Steve
Got a couple 8A Schottkys (200PIV/140RMS forward) and couple 8A silicons (800PIV/560RMS forward) in the TO220 pkg with no place to go, and will mount nicely in place of the selenium. What series "R"/power rating is recommended for either of these parts? At last test, selenium was dropping 20V (120VAC vs 100VDC) Is that common or a defective rectifier. The 3 series resistors 150(143), 720(711) and 1350(1349) ohms are within 10% tolerance. Plan to replace the E caps, but have no measurements on them.
marv
:Marv, I presume that those xfmrs are rated 3.5A on the secondary (low-voltage) winding. The rating on the primaries would then be about 0.35A. That's well within the 10W power consumption of the radio. Still, with voltage regulation, the output voltage would be less than input. Please check the combined xfmr AC output voltage with it loaded by the radio.
:
:But my bet is the selenium rectifier is dropping too much voltage. But if your voltages are also low with battery input, then I'm a little stumped.
:
:In my first response, I mistakenly referred to R13. I should have said R15.
:Doug
:
::The Rad Shak 12.6 VAC xformer is a 3.5A version, the strongest they have.
::
::marv
::
:::Hi Marv,
:::
:::Zenith 5L41 is in Sams 224-18. According to the Sams, filament voltages should be 1.4 VDC, and there shou0ld be 8.3 VDC on pin 7 of the 3V4. B+ on the 1R5 plate should be about 100 VDC. All voltages are measured from the negative end of the filter capacitors, not the chassis. If all voltages are low, suspect the selenium rectifier or the resistor string following the rectifier. Low volatge may keep a marginal oscillator from working.
:::
:::I can drop a copy of the Sams in the mail if you like.
:::
:::Meade
:::
:::
:::*************************************************
:::
::::Forum,
::::Where can I find a free schematic that is readable. My copy from Tech Preservation is very small and wo/pl. Running on AC line, the highest filament measurement is 1.2vdc, and the A+ max is 6.5vdc at pin 7 of the 3V4. On EDD's recommendations, built a batt pack with 10 9 volters and 6 "AA" cells per his posting 3/24/08. All voltages seem 15%-20% low, if I'm reading ??? the numbers correctly. This my 1st AC/DC set, so I'll solve the isolation transformer problem w/2ea 12.6vac Rad Shak parts wired back to back. Radio hums, and worked poorly at first, but now just hum. 1R5 converter measured weak on my tester, so suspect converter inoperable.
::::
::::marv
I don't quite understand the diodes' forward rating? But 8A is more than enough. What happened to your idea of just using a 1N400x?
Doug
:Doug/ALL,
:Got a couple 8A Schottkys (200PIV/140RMS forward) and couple 8A silicons (800PIV/560RMS forward) in the TO220 pkg with no place to go, and will mount nicely in place of the selenium. What series "R"/power rating is recommended for either of these parts? At last test, selenium was dropping 20V (120VAC vs 100VDC) Is that common or a defective rectifier. The 3 series resistors 150(143), 720(711) and 1350(1349) ohms are within 10% tolerance. Plan to replace the E caps, but have no measurements on them.
:
:marv
:
I assume you have replaced the paper caps in the set. If any of the paper caps attached to different points in the filament circuit to B- are leaky it can upset the bias on the tubes. The control grid of the 3V4 is probably biased by the voltage drop across several of the other tubes. If the bias is low on the grid of the 3V4, it can cause that tube to draw too much current.
Radiodoc
*************
:Thanks Doug/Mag,
:Yes, please do mail it, and once again you've pulled me out of the fire. Thanks Meade. My eyeballs are sore from looking at the schem, and trying to decide the voltages. With all tubes in etc, getting 100VDC at the rectifier out. The Rad Shak 12.6 VAC xformer is a 3.5A version, the strongest they have, and I'll pick up some 1N4003's or 1N4004's Can't remember the PIV of either. Finished the Mopar 802 last week, and demo'd it, but not in the car for customer final test/gripes.
:
:marv
:
::Hi Marv,
::
::Zenith 5L41 is in Sams 224-18. According to the Sams, filament voltages should be 1.4 VDC, and there shou0ld be 8.3 VDC on pin 7 of the 3V4. B+ on the 1R5 plate should be about 100 VDC. All voltages are measured from the negative end of the filter capacitors, not the chassis. If all voltages are low, suspect the selenium rectifier or the resistor string following the rectifier. Low volatge may keep a marginal oscillator from working.
::
::I can drop a copy of the Sams in the mail if you like.
::
::Meade
::
::
::*************************************************
::
:::Forum,
:::Where can I find a free schematic that is readable. My copy from Tech Preservation is very small and wo/pl. Running on AC line, the highest filament measurement is 1.2vdc, and the A+ max is 6.5vdc at pin 7 of the 3V4. On EDD's recommendations, built a batt pack with 10 9 volters and 6 "AA" cells per his posting 3/24/08. All voltages seem 15%-20% low, if I'm reading ??? the numbers correctly. This my 1st AC/DC set, so I'll solve the isolation transformer problem w/2ea 12.6vac Rad Shak parts wired back to back. Radio hums, and worked poorly at first, but now just hum. 1R5 converter measured weak on my tester, so suspect converter inoperable.
:::
:::marv
I never did have any luck getting a download from your source. I tried Explorer and Netscape and I already know that I don’t have any luck from that site with “Godzilla” Firefox… plus… additionally trying all of my different Dey- Jah- Voooo converters.
I only got two blank white pages for the PDF converted files.
HOWEVER, a couple of adjunct Zenith chassii, when called up, converted O.K.
What is your present state of difficulty on that most honnable receiver, no workee battery or no workee battery or AC power ???
(BTW.... that batt-AC switching path is right at being a dupe of the Tranoceanic 500 series)
But , not to worry, I now give you the Zenith info…compliments of the esteemed tooth fairy:
73's de Edd
marv
:
:
:
:
:
:
:
:
:
:
:I never did have any luck getting a download from your source. I tried Explorer and Netscape and I already know that I don’t have any luck from that site with “Godzilla” Firefox… plus… additionally trying all of my different Dey- Jah- Voooo converters.
:
:I only got two blank white pages for the PDF converted files.
:
:HOWEVER, a couple of adjunct Zenith chassii, when called up, converted O.K.
:
:
:
:What is your present state of difficulty on that most honnable receiver, no workee battery or no workee battery or AC power ???
:
:
:(BTW.... that batt-AC switching path is right at being a dupe of the Tranoceanic 500 series)
:
:
:
:But , not to worry, I now give you the Zenith info…compliments of the esteemed tooth fairy:
:
:
:
:
:
:73's de Edd
:
:
:
:
:
:
:
:
:
:marv
Marv,
I dropped several 1N4007 diodes in with the schematic and parts list. Mailman picked it up this morning.
Meade
:
::
::
::
::
::
::
::
::
::
::
::I never did have any luck getting a download from your source. I tried Explorer and Netscape and I already know that I don’t have any luck from that site with “Godzilla” Firefox… plus… additionally trying all of my different Dey- Jah- Voooo converters.
::
::I only got two blank white pages for the PDF converted files.
::
::HOWEVER, a couple of adjunct Zenith chassii, when called up, converted O.K.
::
::
::
::What is your present state of difficulty on that most honnable receiver, no workee battery or no workee battery or AC power ???
::
::
::(BTW.... that batt-AC switching path is right at being a dupe of the Tranoceanic 500 series)
::
::
::
::But , not to worry, I now give you the Zenith info…compliments of the esteemed tooth fairy:
::
::
::
::
::
::73's de Edd
::
::
::
::
::
::
::
::
Thanks Meade. Gonna chat with the owner this PM to get the Go-Ahead on my projected repairs.
marv
::Damn Alzheimer!! Went to the Shak for 2 things, transformers and 1N4003's/04's. Just now remembered the diodes. Because of size, ended up w/the 450ma/12.6 xformer, but big V drop. so useless. Oh well, nice to have a couple unused layin around. The sel rectifier is dropping 20 V in to out, and got 98V at the 1st series R. Have not measured the filter caps because its too crowded in that little chassis to unhook them. Right now just tryin to get a heads up on all the problems to respond to customer and order parts. EDD's big schem will help define part values, and THANKS A BUNCH EDD. First time I downloaded that little doc from Tech Preservation, I got the same result of a blank page, but downloaded a new djvu browser, and it was printing OK, although very small.
::
::marv
:
:Marv,
:I dropped several 1N4007 diodes in with the schematic and parts list. Mailman picked it up this morning.
:
:Meade
::
:::
:::
:::
:::
:::
:::
:::
:::
:::
:::
:::I never did have any luck getting a download from your source. I tried Explorer and Netscape and I already know that I don’t have any luck from that site with “Godzilla” Firefox… plus… additionally trying all of my different Dey- Jah- Voooo converters.
:::
:::I only got two blank white pages for the PDF converted files.
:::
:::HOWEVER, a couple of adjunct Zenith chassii, when called up, converted O.K.
:::
:::
:::
:::What is your present state of difficulty on that most honnable receiver, no workee battery or no workee battery or AC power ???
:::
:::
:::(BTW.... that batt-AC switching path is right at being a dupe of the Tranoceanic 500 series)
:::
:::
:::
:::But , not to worry, I now give you the Zenith info…compliments of the esteemed tooth fairy:
:::
:::
:::
:::
:::
:::73's de Edd
:::
:::
:::
:::
:::
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:::