Another amplifier issue! A W530 that has been recapped and any out of tolerance resistors replaced. Tubes all check good. I’m getting about 50% to 60% of gain it should have. I’ve run some tests and found the DC voltages are all low at the tube pins by about 20%. I’ve checked anything I could think of but no luck. Looking for advice as Im not well versed enough to understand where the voltages come from. Can anyone tell me what exactly the 4 section electrolytic capacitor C34 does? I’m suspecting it, as I replaced C35 (the other one) but C34 tested perfect so I left it in, just for now. Any help appreciated, Mauro
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If it’s the 2400 or 2500, there could be a blown fuse in the separate power supply unit in the jukebox.
Shankar Singh
On Aug 22, 2025, at 16:44, M De Simone via Jukebox-list jukebox-list@lists.netlojix.com wrote:
Another amplifier issue! A W530 that has been recapped and any out of tolerance resistors replaced. Tubes all check good. I’m getting about 50% to 60% of gain it should have. I’ve run some tests and found the DC voltages are all low at the tube pins by about 20%. I’ve checked anything I could think of but no luck. Looking for advice as Im not well versed enough to understand where the voltages come from. Can anyone tell me what exactly the 4 section electrolytic capacitor C34 does? I’m suspecting it, as I replaced C35 (the other one) but C34 tested perfect so I left it in, just for now. Any help appreciated, Mauro
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The amp is from a 1900, no Separate power supply. Thank you,
Sent from my iPhone
On Aug 22, 2025, at 5:18 PM, Shankar Singh via Jukebox-list jukebox-list@lists.netlojix.com wrote:
If it’s the 2400 or 2500, there could be a blown fuse in the separate power supply unit in the jukebox.
Shankar Singh
On Aug 22, 2025, at 16:44, M De Simone via Jukebox-list jukebox-list@lists.netlojix.com wrote:
Another amplifier issue! A W530 that has been recapped and any out of tolerance resistors replaced. Tubes all check good. I’m getting about 50% to 60% of gain it should have. I’ve run some tests and found the DC voltages are all low at the tube pins by about 20%. I’ve checked anything I could think of but no luck. Looking for advice as Im not well versed enough to understand where the voltages come from. Can anyone tell me what exactly the 4 section electrolytic capacitor C34 does? I’m suspecting it, as I replaced C35 (the other one) but C34 tested perfect so I left it in, just for now. Any help appreciated, Mauro
Sent from my iPhone _______________________________________________ Jukebox-list mailing list -- jukebox-list@lists.netlojix.com To unsubscribe send an email to jukebox-list-leave@lists.netlojix.com %(web_page_url)slistinfo%(cgiext)s/%(_internal_name)s Searchable Archives: http://jukebox.markmail.org/ _______________________________________________ Jukebox-list mailing list -- jukebox-list@lists.netlojix.com To unsubscribe send an email to jukebox-list-leave@lists.netlojix.com %(web_page_url)slistinfo%(cgiext)s/%(_internal_name)s Searchable Archives: http://jukebox.markmail.org/
On 8/22/2025 4:43 PM, M De Simone via Jukebox-list wrote:
Another amplifier issue! A W530 that has been recapped and any out of tolerance resistors replaced. Tubes all check good. I’m getting about 50% to 60% of gain it should have. I’ve run some tests and found the DC voltages are all low at the tube pins by about 20%. I’ve checked anything I could think of but no luck. Looking for advice as Im not well versed enough to understand where the voltages come from. Can anyone tell me what exactly the 4 section electrolytic capacitor C34 does? I’m suspecting it, as I replaced C35 (the other one) but C34 tested perfect so I left it in, just for now. Any help appreciated, Mauro
Did you test the capacitor up to the rated voltage value? (? 350v 400v 450v) Or did you use one of those handheld DMM ones? If you don't have a schematic and can follow it, well IDK. I've done close to 50 of them and their close cousins, even with proper B+ voltages many had low output. It was the AVC circuit.
To do it right, you should replace that one cap that you skipped. I think, but don't know, did the small value (.001 - .5) caps back then sometimes leak a little from new? I'd really like to know. Within specs, but a little leaky.
Tony, Thanks for the reply, I have the manual and enlarged schematics for the amplifier. I’m just wondering what could be pulling down my voltage. If it’s not C34 then I’d like to know if there are any other suspects before i put it back in the jukebox. I also believe it may have something to do with the AGC circuit as well, when you first turn it on the voltage is up where it should be but after a few 5 seconds or so it drops low. That’s on the bench but when I hook it up to the mech it’s starts playing loud and then diminishes to the lower level. Thanks for the suggestion,
Sent from my iPhone
On Aug 22, 2025, at 5:38 PM, Tony Miklos via Jukebox-list jukebox-list@lists.netlojix.com wrote:
On 8/22/2025 4:43 PM, M De Simone via Jukebox-list wrote: Another amplifier issue! A W530 that has been recapped and any out of tolerance resistors replaced. Tubes all check good. I’m getting about 50% to 60% of gain it should have. I’ve run some tests and found the DC voltages are all low at the tube pins by about 20%. I’ve checked anything I could think of but no luck. Looking for advice as Im not well versed enough to understand where the voltages come from. Can anyone tell me what exactly the 4 section electrolytic capacitor C34 does? I’m suspecting it, as I replaced C35 (the other one) but C34 tested perfect so I left it in, just for now. Any help appreciated, Mauro
Did you test the capacitor up to the rated voltage value? (? 350v 400v 450v) Or did you use one of those handheld DMM ones? If you don't have a schematic and can follow it, well IDK. I've done close to 50 of them and their close cousins, even with proper B+ voltages many had low output. It was the AVC circuit.
To do it right, you should replace that one cap that you skipped. I think, but don't know, did the small value (.001 - .5) caps back then sometimes leak a little from new? I'd really like to know. Within specs, but a little leaky.
-- Tony Miklos Tony's Jukebox Repair
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On 8/22/25 15:28, M De Simone via Jukebox-list wrote:
Tony, Thanks for the reply, I have the manual and enlarged schematics for the amplifier. I’m just wondering what could be pulling down my voltage. If it’s not C34 then I’d like to know if there are any other suspects before i put it back in the jukebox. I also believe it may have something to do with the AGC circuit as well, when you first turn it on the voltage is up where it should be but after a few 5 seconds or so it drops low. That’s on the bench but when I hook it up to the mech it’s starts playing loud and then diminishes to the lower level.
That indeed sounds like an AGC issue.
Note that the 530 amp for the 1900 uses a Cobra cartridge. These can be really tricky to get working properly. There's a damping compound that dries out and decent aftermarket cartridges are hit and miss. They also aren't particularly kind to stereo records.
Many of these amps have been modified to use ceramic cartridges which typically involves swapping the tonearm for a later stereo one. If yours has been modified, look at the way the modification has been done, this could be the issue.
Jay, That’s a good point, This particular amplifier is bone stock original, only thing I see is one cap changed at some point on the plate of a 6L6. It’s never been touched. I’ve done that mod once so would probably have recognized the changes. I wish I could figure out which component might do this or which area to focus on. I can read the schematic but don’t know what each component does. I verified the problem by swapping in another 530 amplifier and it was indeed louder.
Sent from my iPhone
On Aug 22, 2025, at 6:45 PM, Jay Hennigan via Jukebox-list jukebox-list@lists.netlojix.com wrote:
On 8/22/25 15:28, M De Simone via Jukebox-list wrote:
Tony, Thanks for the reply, I have the manual and enlarged schematics for the amplifier. I’m just wondering what could be pulling down my voltage. If it’s not C34 then I’d like to know if there are any other suspects before i put it back in the jukebox. I also believe it may have something to do with the AGC circuit as well, when you first turn it on the voltage is up where it should be but after a few 5 seconds or so it drops low. That’s on the bench but when I hook it up to the mech it’s starts playing loud and then diminishes to the lower level.
That indeed sounds like an AGC issue.
Note that the 530 amp for the 1900 uses a Cobra cartridge. These can be really tricky to get working properly. There's a damping compound that dries out and decent aftermarket cartridges are hit and miss. They also aren't particularly kind to stereo records.
Many of these amps have been modified to use ceramic cartridges which typically involves swapping the tonearm for a later stereo one. If yours has been modified, look at the way the modification has been done, this could be the issue.
-- Jay Hennigan - jay@west.net Network Engineering - CCIE #7880 503 897-8550 - WB6RDV
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On 8/22/2025 5:38 PM, Tony Miklos wrote:
On 8/22/2025 4:43 PM, M De Simone via Jukebox-list wrote:
Another amplifier issue! A W530 that has been recapped and any out of tolerance resistors replaced. Tubes all check good. I’m getting about 50% to 60% of gain it should have. I’ve run some tests and found the DC voltages are all low at the tube pins by about 20%. I’ve checked anything I could think of but no luck. Looking for advice as Im not well versed enough to understand where the voltages come from. Can anyone tell me what exactly the 4 section electrolytic capacitor C34 does? I’m suspecting it, as I replaced C35 (the other one) but C34 tested perfect so I left it in, just for now. Any help appreciated, Mauro
Did you test the capacitor up to the rated voltage value? (? 350v 400v 450v) Or did you use one of those handheld DMM ones? If you don't have a schematic and can follow it, well IDK. I've done close to 50 of them and their close cousins, even with proper B+ voltages many had low output. It was the AVC circuit.
To do it right, you should replace that one cap that you skipped. I think, but don't know, did the small value (.001 - .5) caps back then sometimes leak a little from new? I'd really like to know. Within specs, but a little leaky.
Tony, I didn’t test the paper capacitors, I just replaced them all. I tested the multi section can capacitors with an esr tester and C34 tested like a new capacitor but C35 was bad. I will change it soon anyway but for testing purposes I did not think it would be an issue, the amplifier has no hum whatsoever. Mauro
Sent from my iPhone
On Aug 23, 2025, at 6:33 AM, Tony Miklos via Jukebox-list jukebox-list@lists.netlojix.com wrote:
On 8/22/2025 5:38 PM, Tony Miklos wrote:
On 8/22/2025 4:43 PM, M De Simone via Jukebox-list wrote: Another amplifier issue! A W530 that has been recapped and any out of tolerance resistors replaced. Tubes all check good. I’m getting about 50% to 60% of gain it should have. I’ve run some tests and found the DC voltages are all low at the tube pins by about 20%. I’ve checked anything I could think of but no luck. Looking for advice as Im not well versed enough to understand where the voltages come from. Can anyone tell me what exactly the 4 section electrolytic capacitor C34 does? I’m suspecting it, as I replaced C35 (the other one) but C34 tested perfect so I left it in, just for now. Any help appreciated, Mauro
Did you test the capacitor up to the rated voltage value? (? 350v 400v 450v) Or did you use one of those handheld DMM ones? If you don't have a schematic and can follow it, well IDK. I've done close to 50 of them and their close cousins, even with proper B+ voltages many had low output. It was the AVC circuit. To do it right, you should replace that one cap that you skipped. I think, but don't know, did the small value (.001 - .5) caps back then sometimes leak a little from new? I'd really like to know. Within specs, but a little leaky.
-- Tony Miklos Tony's Jukebox Repair
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I'm not sure if I got my posts mixed up between the two 530 amp posts. So if it doesn't make sense, ignore it.
That's good that you replaced all of the paper caps, but when doing so, also include new filter caps no matter what they read. Just in case you don't know, it's rare, but sometimes the caps in cans have internal shorts/leakage from one cap to the other. Be sure to jumper all caps that aren't being tested to ground when testing them for both capacitance and leakage. And again, if the cap is rated for 450v, then the tester must put 450 volts onto the capacitor. While testing the leakage, measure the voltage from the cap lead to ground. With a decent tester, they normally go to a voltage higher than the rated voltage. But like said, just replace it anyway.
On 8/23/2025 7:52 AM, M De Simone via Jukebox-list wrote:
Tony, I didn’t test the paper capacitors, I just replaced them all. I tested the multi section can capacitors with an esr tester and C34 tested like a new capacitor but C35 was bad. I will change it soon anyway but for testing purposes I did not think it would be an issue, the amplifier has no hum whatsoever. Mauro
Sent from my iPhone
On Aug 23, 2025, at 6:33 AM, Tony Miklos via Jukebox-list jukebox-list@lists.netlojix.com wrote:
On 8/22/2025 5:38 PM, Tony Miklos wrote:
On 8/22/2025 4:43 PM, M De Simone via Jukebox-list wrote: Another amplifier issue! A W530 that has been recapped and any out of tolerance resistors replaced. Tubes all check good. I’m getting about 50% to 60% of gain it should have. I’ve run some tests and found the DC voltages are all low at the tube pins by about 20%. I’ve checked anything I could think of but no luck. Looking for advice as Im not well versed enough to understand where the voltages come from. Can anyone tell me what exactly the 4 section electrolytic capacitor C34 does? I’m suspecting it, as I replaced C35 (the other one) but C34 tested perfect so I left it in, just for now. Any help appreciated, Mauro
Did you test the capacitor up to the rated voltage value? (? 350v 400v 450v) Or did you use one of those handheld DMM ones? If you don't have a schematic and can follow it, well IDK. I've done close to 50 of them and their close cousins, even with proper B+ voltages many had low output. It was the AVC circuit. To do it right, you should replace that one cap that you skipped. I think, but don't know, did the small value (.001 - .5) caps back then sometimes leak a little from new? I'd really like to know. Within specs, but a little leaky.
-- Tony Miklos Tony's Jukebox Repair
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