Pioneer stereo amp is blowing fuses, need suggestions

[the_badcliff]

I have a Pioneer Stereo amp, model SX-525, that I've been trying to get into working condition.  Its a well built and nice looking old amp so I'd love to get it working rather than buy a new one.

Anyway, it has been blowing fuses on its right channel.  I'm hoping someone here may have some suggestions of what I should investigate, as I don't really know where to start.

I know its not a stompbox, but maybe somebody can help.  Thanks.

[Fret Wire]

Most likely the electro's are old, and one has failed or shorted. Check diodes also. Have you popped off the cover and taken a look under the hood yet?

http://spaghoops.com/grundig/hifi.htm

[mikeb]

If it's not about FX then it should be in the lounge.....

That said, it's a power supply problem. There's an abnormally high current drain that's causing the fuses to pop. You need to checkout what devices (caps, resistors, transistors) are attached to the voltage rails (you can do this by performing a continuity test between a known V+ rail and all components, making note of which ones are connected). I'd be guessing that the component causing the short might be visually damaged - or at least this is worth checking. Yes, just replacing all the electros is worth a shot and even if it doesn't fix things it's something you'll want to do anyway. If you have a left channel, you can compare voltages in the circuit (if the fuse gives you enough time to wire things up). Just be careful of the DC lines, likely you've got some relatively high voltages in there! Also, if you can sus it out, you can isolate sections of the amp circuit by temporarily cutting traces or desoldering components ... a bit of trial and error and thinking will likely see you clear, most amps are quite simple and easily repaired.

Good luck!

Mike

[the_badcliff]

Good ideas.  Yes, I have looked under the hood, I had thought the volume pot was damaged because the right channel would scratch when I turned it.  Contact cleaner didn't work, and thats when I discovered the fuse was broken.  When I replace the fuse and turn the amp on there is a bassy pop before the right channel fails altogether (this all happens instantaneously).   The left channel sounds great.

Anyway, I will need to run over to my parents house to grab the schematic.  Then I'll test any suspect components.

Thanks for your help, and I won't be insulted if Aron wants to move this to the lounge, I didnt know.