A friend of mine gave me a Samson sx1200 than need to be repaired. He said to me that the left channel has low and distorted volume and the right one has high and distorted volume.
I have done a first visual inspection, and everything looks fine, no burned resistor or mosfet.
After a bit of googling I have found the schematics of the amp, and I have started to check the power board.
At B+ and B- I have +- 88 Volts, and that's sounds fine. I have also check the other rail, and everything looks ok. I have +-15v on terminals 3 and 5 of Wa102/a and +-24 on terminals 5 and 6 of cn302.
I have tried to connect one channel per time, and the result is the same. The audio is "flat", metallic, its like a 10kbps mp3, with no bass and only high freq.
This is not the first time that I "play" around with power amps, but I have never troubleshooted one, so I need some help. What should I check now? I have all the equipment needed, oscilloscope, function generator and DMMs, but I do not know what is the best way for testing it.
I have done a first visual inspection, and everything looks fine, no burned resistor or mosfet.
After a bit of googling I have found the schematics of the amp, and I have started to check the power board.
At B+ and B- I have +- 88 Volts, and that's sounds fine. I have also check the other rail, and everything looks ok. I have +-15v on terminals 3 and 5 of Wa102/a and +-24 on terminals 5 and 6 of cn302.
I have tried to connect one channel per time, and the result is the same. The audio is "flat", metallic, its like a 10kbps mp3, with no bass and only high freq.
This is not the first time that I "play" around with power amps, but I have never troubleshooted one, so I need some help. What should I check now? I have all the equipment needed, oscilloscope, function generator and DMMs, but I do not know what is the best way for testing it.
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The questions you ask usually cannot be answered with in a post or two ...It requires that you already " have " the procedure .
KTC3200 transistors fail for no reason quite common
Fusible resistors here and there go open also quite common
R133,R120,R115 and others ....
Measure if there is bias in the amplifier,
measure if there is offset in the amplifier,
Feed the amp with no load conditions khz sine wave, observe output, see what is missing from the original signal, see where signal gets lost, upper wave form will mean positive side lower the negative ...
Kind regards
Sakis
KTC3200 transistors fail for no reason quite common
Fusible resistors here and there go open also quite common
R133,R120,R115 and others ....
Measure if there is bias in the amplifier,
measure if there is offset in the amplifier,
Feed the amp with no load conditions khz sine wave, observe output, see what is missing from the original signal, see where signal gets lost, upper wave form will mean positive side lower the negative ...
Kind regards
Sakis
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