Fixing blown Crate CR-IIR Solid State Amp

[tortuga]

I am trying to fix a Crate CR-IIR that I recently acquired. I have dug up quite a few schematics, but am not sure which one would be well suited since I have not found the one of the exact make and model.

As of now, the amplifier will not power up. The 2 amp fuse blew, and upon inspection, it looks like some of the diodes were burnt up, but most of the parts are not charred. I have gone through sections of the amp with my multi-meter and continuity tester.  There are three perf boards. One looks like the preamp and tone stack to me. The The second is part of the power amp I believe. The third is the caps that go out? I'm not really sure.

I have experience with building kits and circuits, but have never really gone through troubleshooting a circuit, and have been doing a lot of reading on this as of lately.

Any help or advice would be greatly appreciated. I really happened to like the sound of this amp until it went up in smoke!

P.S. I don't know if pictures of the circuit board would be helpful, but I could post them as well since I don't have the original schematic.

[joecool85]

Last time I had this happen the power amp chip had blow and took out with it the rectifying diodes and fuse.  I replaced the TDA20XX chip, rectifying diodes and fuse and away I went.

So you were playing this amp when it died?  Did you have the proper speaker hooked up to it?  Did the speaker blow?  Were you playing it loudly when it died?

[Enzo]

The CR-IIR is way older than TDA20xx.

This thing is a very early Crate amp.  1979 or so.  Discrete transistor output stage.  STart checking those power transistors for shorted.  Make sure the power supply rectifiers are not shorted.