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
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/