"Arfa Daily" wrote in message
...
Hi all

Anyone by any chance got schematics for an old Pioneer unit type DC-X55Z ?
Only need the bit around the output hybrid and its power supplies, I
think. The hybrid has audio going in at both channel input pins, but not a
jot coming out on either channel. Basic supplies are present, and no
obvious looking anomalies at any pin using the data sheet for the STK.
It's not the STK itself, as I hung another in just to be sure.
Interestingly, the output protect circuit doesn't seem to be working
either as the output relay is never being driven, but there is no
significant DC offset on either channel's output, so I'm guessing that
there is going to be an O/C resistor or whatever that has some commonality
between the protect circuit, and something like the mute pin on the STK,
which has about negative 1 volt on it. I can't find anything on the data
sheet that details the conditions on this pin for muted or opened.

TIA

Arfa

Not finding the manual for that, not free anyway, but sometimes I'll see a
small value electrolytic hanging off the power supply and used as a fast
cut-off for the protection circuit. Bad cap, IC sees AC (or zero DC anyway)
and keeps the relay drive held off. Usually between 2.2uF and 10uF.

You could try forcing the relay drive ON, using the diode check function of
your DMM to the drive transistor base, for example. If the amp output is
normal I do think I'd look more back to the power supply.

Mark Z.