smoke on ampeg v4 and Twin Rev vintage

[hbann]

Please,someone can help me? After a loong time with no use I turn it on, and after a few seconds a lot of white smoke springs from the back of the amp...first time was the Fender twin reverb and next time the Ampeg V4 bass head ,both 1977...
I live in Brazil and its hard to find a tech.who knows how to fix these vintage amps here.Thanks l lot for any help.

[defaced]

I am a very inexperienced amp builder, but I would say you fried your filter caps. This is because after a long amount of time without use or charge, the dielectric in the cap dries up and when hit with high voltage, it fries the cap. If you open the chassis, you should be able to see the damage done to the caps.

[mikeboone]

You should check your wall voltage too. Both amps' filter caps going bad is wierd, but certainly possible. Defaced's theory is certainly a good one.

I would re-cap both amps if they havent been done in recent years.

[hbann]

Thanks for the reply.Examine or change filter caps cause any risk of electricity shock even when the amp is unplugged ?Or they could hurt me?
Thanks!
Helena

[defaced]

They could kill you. There have been a couple of discussions recently about bleeding filter caps and how to measure to see if they are still charged.

[Bruce / Mission Amps]

Do you have access to a digital camera where you can show us the inside of the amp?
Both these amps are known for burning their screen resistors up when a power tube goes bad and we'd probably be able to see that in a picture of the inside, showing the power tube sockets.
If you are unfamiliar with high voltage vacuum tube amps, I'd be very very careful here.
I've been doing this since I was a kid so make sure you do research on how to work on them safely!
It still amazes me how many times I've forgotten to unplug a big ass vacuum tube amp where I am one second away from working on an open chassis.
At least take the time to learn how to drain the power supply capacitors... etc.

[hbann]

photos

Ok, I will post some photos .Thanks for help me.
Helena