ampeg gs12r reverberocket problems

[goldnmold]

Hello! I'm a returning member from the old ampage forum, glad to see we're still alive! I have a 60 something reverberocket 2 that seems to be all original except for the speaker. I've always thought the reverb sounded totally weak, but my real problem now is much worse. I lent the amp out to a friend to use in the studio recording his album (which did very very well, jools holland the whole bit) and when I got it back, it sounded increasingly weak and fizzly, distorted and quiet. I swapped the preamp tubes, and replaced the 7591s with new JJ's. Still no good. If I crank it to 10 it sounds ok, but thats because its all so dirty you can't tell. There's no bad hum or excess noise. I'm having trouble getting the chassis out with those wacky screws, so I haven't been inside yet. What should I look for? I'd like to bring the reverb back to life too, and convert to a 3 prong cord. Thanks!

[Chuck H]

Sounds like the amp is just due for some heavy maintenance after being put through some paces. Replace ALL electrolytic caps and check film caps for leakage. Check old resistors for drift outside the original tolerance (probably 20%) and replace any resistors or film caps that are out of spec. You have the tubes, should any need replacing after testing and measuring bias current and performance. This and put the three prong cord in and the amp should be good for another fifty years. Well, not really... Old tube sockets will need to be cleaned and retentioned, or at worse replaced. An components NOT replaced will have some wear obviously. But snuffing the amp up shpuld restore performance and reliability to an acceptible and even above average level in that amp.