EEVblog Electronics Community Forum
Electronics => Repair => Topic started by: jordanp123 on March 08, 2018, 11:09:42 pm
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Had two bad pots on the front dials, got those replaced and channel B on the amplifier is perfect. Channel A, however is less than so. It almost sounds like clipping in the circuit; as the volume is turned up the sound becomes very distorted, I can bond the two channels and use the input in channel A, but the output on B and everything sounds fine. It has to be something in the amplification circuit, I've tried finding a service manual or a schematic for this unit but no luck. Any body have any previous experience with these units ?
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Hifi manuals seems to have a schematic. You need to sign up though - I do not have an account and did not try to download data from that site, but seems to be free of charge. Maybe sign up with a throw away mail address first ;)
http://www.hifi-manuals.com/Peavey-Electronics/GPS-1500/downloads (http://www.hifi-manuals.com/Peavey-Electronics/GPS-1500/downloads)
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Greatly Appreciated !
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Good thing is, you have a working channel as reference. That way you could follow the signal path and check for differences. Usually there is some order of failing in amplifier parts. The main suspects are: Bleeding electrolytic caps, then diodes and transistors. Power electronics are also often the first parts to fail due to thermal stress, but since you get output through the power stage, maybe look at the preamp circuit first. Resistors, ceramic caps,... tend to be more robust. Do some thorough visual inspection of the caps first (and burnt parts of course).
Good luck hunting that down :)
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I've called Peavey in the past, and they will usually email you a schematic or service manual. Usually either free or a nominal fee.
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Got it. Followed the print back, check transistors along the way. This transistor had a small crack in the base lead. Appreciate the help everyone !
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Good catch! Pro and guitar/bass amps tend to have problems due to shock and vibration. I can tell you as a former gigging musician that the gear didn't go back into the van at the end of the gig with the same care it went in.