Static on Right Channel Realistic SPA-100

[d1ck]

So I've recently been given a Realistic SPA-100 Integrated Amp that I'd like to try and repair. There are two main problems with the unit:

1. The right channel is very static-y and seems to get worse with heavy bass, but it is still noticeable with the lower freq in the eq turned all the way down. The static seems to come and go randomly, and the volume through that channel seems to be a little lower than the right channel.

2. There is a hiss in the background which is only noticeable when there is no sound playing.

I've pulled the top off the unit, and I don't see any visible damage (big surprise right? ) I've taken some pictures of the internals to show you what I'm working with which I will post tonight.

I'm basically just wondering where to start troubleshooting? I've got a multi meter and access to one of those fancy digital soldering irons if necessary. I hope someone can point me in the right direction, as I'd love to get this amp working with my Energy C-3's instead of the craptastic Logitech Z5500 amp which I'm using now.

[d1ck]

[image]http://dl.dropbox.com/u/4384741/20111121_134438.jpg[/image]
[image]http://dl.dropbox.com/u/4384741/20111121_134458.jpg[/image]
[image]http://dl.dropbox.com/u/4384741/20111121_134513.jpg[/image]
[image]http://dl.dropbox.com/u/4384741/20111121_134537.jpg[/image]
[image]http://dl.dropbox.com/u/4384741/20111121_134547.jpg[/image]
[image]http://dl.dropbox.com/u/4384741/20111121_134601.jpg[/image]
[image]http://dl.dropbox.com/u/4384741/20111121_134614.jpg[/image]
[image]http://dl.dropbox.com/u/4384741/20111121_134625.jpg[/image]

[kevinkr]

Moving to solid state since this is not a chip amp..

[d1ck]

Sorry about that

[d1ck]

Bump

[johnr66]

Does the hiss go with the volume all the way down?

It may need the controls cleaned and/or it may need other parts. Hard to say without more diagnostics.

[d1ck]

The noise stays in the background even with the volume turned all the way down. Also, what type of diagnostics?

[sofaspud]

Without an o'scope, it might be most productive to signal trace the circuit until you find/lose the static. Since the noise remains with the volume all the way down, its origin is therefore after the volume potentiometer.

[d1ck]

How would I go about finding the static? Is it a signal which can be found with a multimeter?

[sofaspud]

1) Hunting it down is about the only way.
2) I'm afraid it isn't likely.
Are you familiar at all with the signal injection/tracing troubleshooting technique?
If not, you're not alone. It's an easily understood concept and building the test equipment isn't difficult. IMHO it really is something those new to diy audio should seriously consider building.
This Signal Tracer provides good diy details.
The signal injector would probably be of more use in finding your problem. You could inject a signal into each transistor base/gate in the audio path, eventually finding the point where the static appears/disappears (you can go from output to volume pot or volume pot to output, it doesn't really matter). Not very difficult, but it requires some patience. "The static seems to come and go randomly" is more of a problem. Make sure you've gotten the static going before you start the troubleshooting.