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Electronics Repair (sci.electronics.repair) Discussion of repairing electronic equipment. Topics include requests for assistance, where to obtain servicing information and parts, techniques for diagnosis and repair, and annecdotes about success, failures and problems. |
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#1
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Niles SI-275 amplifier
Had this unit come in, and it would shut down (protect) with any audio
source connected. Found some bad solder joints on the emitter resistors, resoldered those and everything was OK when I bench tested it. The unit just came back in after a week, and is going into protect again. It will play at low volume fine, but when you turn it up it shuts down, when it does you can watch the protect light flash in time with the beat of the music. No DC bias on the output, nothing abnormal, and if you tap audio off before the speaker relay it sounds fine. Obviously a fault in the protection circuit, however everything checks OK. I traced grounds, checked all components of the protect circuit that I could find without a schematic. Has anyone seen this symptom before? More specifically does anyone have a schematic? Jammy |
#2
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Niles SI-275 amplifier
"ampdoc" wrote in message ... Had this unit come in, and it would shut down (protect) with any audio source connected. Found some bad solder joints on the emitter resistors, resoldered those and everything was OK when I bench tested it. The unit just came back in after a week, and is going into protect again. It will play at low volume fine, but when you turn it up it shuts down, when it does you can watch the protect light flash in time with the beat of the music. No DC bias on the output, nothing abnormal, and if you tap audio off before the speaker relay it sounds fine. Obviously a fault in the protection circuit, however everything checks OK. I traced grounds, checked all components of the protect circuit that I could find without a schematic. Has anyone seen this symptom before? More specifically does anyone have a schematic? Jammy Doesn't have an intelligently controlled fan by any chance, does it ? Arfa |
#3
Posted to sci.electronics.repair
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Niles SI-275 amplifier
"Arfa Daily" wrote in message ... "ampdoc" wrote in message ... Had this unit come in, and it would shut down (protect) with any audio source connected. Found some bad solder joints on the emitter resistors, resoldered those and everything was OK when I bench tested it. The unit just came back in after a week, and is going into protect again. It will play at low volume fine, but when you turn it up it shuts down, when it does you can watch the protect light flash in time with the beat of the music. No DC bias on the output, nothing abnormal, and if you tap audio off before the speaker relay it sounds fine. Obviously a fault in the protection circuit, however everything checks OK. I traced grounds, checked all components of the protect circuit that I could find without a schematic. Has anyone seen this symptom before? More specifically does anyone have a schematic? Jammy Doesn't have an intelligently controlled fan by any chance, does it ? Arfa No, no fan. Found the problem. C30, 220uf 25v non-polar in the DC detect circuit near the speaker relay. Thanks! Jammy |
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