Peavey XR600C PA amp problem
Just wondering if anyone has ever seen this particular problem befo
When I exceed a certain output level, the volume begins to modulate from normal to almost zero in a smooth, cyclic manner. This occurs at a rate of around 0.5/S- almost like a very slow tremolo circuit. I haven't cracked it open yet, but I'm guessing it has something to do with a negative feedback circuit gone bad, or maybe just a power supply issue. Whatever it is it only happens when the output level reaches a certain (fairly low) amplitude. Below that it works fine. Any guesses? Bad PS cap? Thanks, Sam |
Peavey XR600C PA amp problem
If there is a compressor/limiter circuit, it may be kicking in even if
turned off. "Sam Lloyd" wrote in message ... Just wondering if anyone has ever seen this particular problem befo When I exceed a certain output level, the volume begins to modulate from normal to almost zero in a smooth, cyclic manner. This occurs at a rate of around 0.5/S- almost like a very slow tremolo circuit. I haven't cracked it open yet, but I'm guessing it has something to do with a negative feedback circuit gone bad, or maybe just a power supply issue. Whatever it is it only happens when the output level reaches a certain (fairly low) amplitude. Below that it works fine. Any guesses? Bad PS cap? Thanks, Sam |
Peavey XR600C PA amp problem
That's one of the possibilities I was thinking of when I mentioned neg
FB, but it doesn't have any compressor/limiter built in, at least not an adjustable type. I checked the PS rails, and the voltage drops as the output increases until the point where the "modulating" starts. I found that if I increase the volume VERY slowly I can sometimes avoid the modulation and achieve high output levels. I scoped the rails and they vary along with the modulation. Tried substituting some different power caps, but no difference. I also found that there's about .65 VDC offset at the spkr output, FWIW- don't see any pot for adjusting the DC offset. I've emailed Peavey, so hopefully they'll send a schem tomorrow, and help illuminate the mystery. Sam taGroover wrote: If there is a compressor/limiter circuit, it may be kicking in even if turned off. "Sam Lloyd" wrote in message ... Just wondering if anyone has ever seen this particular problem befo When I exceed a certain output level, the volume begins to modulate from normal to almost zero in a smooth, cyclic manner. This occurs at a rate of around 0.5/S- almost like a very slow tremolo circuit. I haven't cracked it open yet, but I'm guessing it has something to do with a negative feedback circuit gone bad, or maybe just a power supply issue. Whatever it is it only happens when the output level reaches a certain (fairly low) amplitude. Below that it works fine. Any guesses? Bad PS cap? Thanks, Sam |
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