Hi,
One of my friend has had a PV Classic 30 for 15 years or so (give or take a few) and he told me it kept blowing tubes. The closest tech told him it was most likely the bias but didn't want to work on that kind of stuff (how nice). So, this friend, knowing that I know a bit about amps brought it to me hoping that I could help.
I fired the amp up tonight and all the tubes were glowing nicely with some blue in them... I bought a new EL84 quad so I put 'em in there. Fired the amp again and it worked nicely for about a minute (man, that amp sure sounds sweet when overdriven!).
Here's the interesting part: After that minute, the volume started going down just like it would if the amp would've been turned off. It didn't behave like a blown tube (which I've experienced more than a few times). It was just a smooth gradual volume drop until nothing came out (just like an amp draining after being shut down with the standby still on "operate"). The power tubes didn't glow anymore even though the amp was still on and the pre-amp tubes were glowing still.
I pulled out and pushed-in each tube, fired the amp up and the same phenomenon happened again (I was playing softer so I heard a faint "click" right before the volume started to drop), only this time I can't get it to work no more... The amp powers up, the pre-amp tubes are glowing but there's not a spec of light in any of the 4 power tubes.
I'm discarding the bias/blown tubes theory since none of the tubes seem to even have current flowing through.
Any thought on what could be wrong here? I'm gonna open it up to see if there's some faulty connection around the sockets and such but that "U" shaped board is such a PITA to work on that I'd like to know if any of you have any clue to give me a headstart.
Thanks a lot guys!
One of my friend has had a PV Classic 30 for 15 years or so (give or take a few) and he told me it kept blowing tubes. The closest tech told him it was most likely the bias but didn't want to work on that kind of stuff (how nice). So, this friend, knowing that I know a bit about amps brought it to me hoping that I could help.
I fired the amp up tonight and all the tubes were glowing nicely with some blue in them... I bought a new EL84 quad so I put 'em in there. Fired the amp again and it worked nicely for about a minute (man, that amp sure sounds sweet when overdriven!).
Here's the interesting part: After that minute, the volume started going down just like it would if the amp would've been turned off. It didn't behave like a blown tube (which I've experienced more than a few times). It was just a smooth gradual volume drop until nothing came out (just like an amp draining after being shut down with the standby still on "operate"). The power tubes didn't glow anymore even though the amp was still on and the pre-amp tubes were glowing still.
I pulled out and pushed-in each tube, fired the amp up and the same phenomenon happened again (I was playing softer so I heard a faint "click" right before the volume started to drop), only this time I can't get it to work no more... The amp powers up, the pre-amp tubes are glowing but there's not a spec of light in any of the 4 power tubes.
I'm discarding the bias/blown tubes theory since none of the tubes seem to even have current flowing through.
Any thought on what could be wrong here? I'm gonna open it up to see if there's some faulty connection around the sockets and such but that "U" shaped board is such a PITA to work on that I'd like to know if any of you have any clue to give me a headstart.
Thanks a lot guys!
Last edited:
