Accuphase E202 stop working

[hc167]

hi:

Hope someone can help me. My Accuphase E202 is stopped working about two weeks ago. and my brother told me that when he switched on the amp, he hear some "pop pop .." from the speaker and the meter go all the way to the right. And then he shut it off. I told him to make sure he can hear the relay is working by verify the click sound. So he put the "speaker selection" switch to off position. and he turned it on again. Obviously, no "pop" sound from the speaker. Then the needles at the meter still go all the way to the right. and he hear "click" sound from the relay. However, he saw some smoke coming out from near the heatsink region. So I would imagine the power transitors are gone.

OK, here is my question. this is a 30 yrs old amp and I would assume that I will most likely not going to get the original part. So what power transitors will be good substitution for the original one? Second question, do power transitors usually have life time of about 30 years?

[jhal]

Sounds like there is more wrong than just a bad output transistor. I would imagine it's safe to say this unit has TO3 case outputs, which tend to "hold their smoke" even when they fail, since they use no plastic in their construction. Something failed from thousands of thermal cycles and many more thousands of hours of use. It could have been something as simple as a shorted electrolytic capacitor. Of course, when one simple component fails, they often cause cascade failures throughout the amplifier. Turning it back on after the initial failure sounds like it caused more damage. The fact that the protection circuit tripped when it was turned back on the second time indicates an unsafe voltage appeared out the speaker terminals. That, was probably the outputs failing, most likely, caused by the initial failure of a part "upstream". To answer your question, all components have a finite life span. The enemy of electronics is heat. There are too many variables to put a specific time span on the life of an electronic component. Whatever you do, do not turn this amp back on until you have it looked at by a vintage-experienced competent tech.

[hc167]

you are right. I have not yet inspected by myself. Everything was done by my brother. anyway, I did all the recapping. So I would imagine that all cap are fine. I just want to find out what are the possible substitution for the power trans for the meantime so that I can be prepare before I work on the amp. By the way, is it good idea to matched the output power trans since I will be working on it?

[jhal]

Yes, transistor pairs for the drivers, pre-drivers, and outputs much be matched or it will almost certainly be unstable and prone to oscillation and "refailure".

I'm sure someone with more experience than me and possibly someone who knows that specific amp well, will chime in and answer your questions clearer then I can.:yes:

[inductor]

funny that just bought a faulty 202 meself !, so its been recapped, did it work ok after the recapping ? the fact you are asking here what to do means you probably wont be able to sort it !

[hc167]

no, I own this amp for about two years already. and I did recapped when I bought it (back in two years ago). So I don't really get what you mean.