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

"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

"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