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Yamaha YTA 95

3/30/2006 12:25 AM
Lee Yamaha YTA 95
I've just aquired this amp in a non-working condition. It's a 100w(?) solid state 2x12 combo from the late 70's/early 8o's. I plugged it in and got a loud continous hum (this is unaffected by changing settings/turning pots etc). The guy I got it from said it's been in a cupboard for years. He said the last time it was working it just cut out and never worked again. This is all I know about the amp and after hours and hours of internet searches, I have found zero info on this model. Can anyone shed any light on what may be the problem or how to go about diagnosing it? Any info at all about this amp would be gratefully received. Many Thanks.
3/30/2006 1:52 AM

You can probably buy the service manual from Yamaha.  
Those solid state amps are pretty generic. Your "loud hum" may be DC on the speaker. Does the cone move one way and stay there when you power up the amp? Or disconnect the speaker and power up and see if DC sits on the speaker wires.  
If so, you likely have a shorted output transistor.  
Otherwise, I'd be looking for a bad filter cap, or one cracked free of its solder.
3/30/2006 8:53 PM
Hi Enzo  
Many thanks for the reply. I'll use that as a starting point. Fingers crossed!
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