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Old 27th September 2010
Gear Addict
Steck's Avatar

Okay, the low-hanging fruit would be:

1) If you have a voltmeter, check the power supply voltages. This is easiest done without service docs by looking for either labeled "test points" that are labeled as such. *or*....

If there's no labeled test points, look for integrated circuits that are commonly available. for example 4558 or or TLO072 or LF356 or 4052 chips (there's many beyond this), which have standard pin-outs. See one of the sticky posts on this this board for a site that has this type of info. (I have one of these, but I've never popped the cover, so I can't give you specific places to check).

2) With the power off and the unit unplugged, verify you don't see any electrolyic caps that are "bulging" or "puffy" (note to self, need some pictures!). If that's the case, they could be shorted out, and causing the difficulty. To repair them, if you can still read the writing on the case of the cap, you can obtain replacements, then desolder the old ones and put new ones in. (Hopefully that fixes the problem....) (do you have experience soldering and desoldering? If not, you're going to need help from someone).

3) With the power off and the unit unplugged, push down on every integrated circuit, and make sure they're fully seated. They can "walk" out of the socket with repeated power-cycling (going from cold to warm and back).

4) With the power off and the unit unplugged, unplug and replug every connector that goes between all the various boards and assemblies in the unit. Be careful, as some connectors such as the flexible circuit board type, are tricky, and easy to break.

There's folks selling service manuals for audio gear on eBay, if you're not able to find anything else. That'll help because you'll then have a schematic, and perhaps a block diagram, and so forth.