Dave wrote:

"Mark D. Zacharias" wrote in message
et...

Arfa Daily wrote:

"Mark D. Zacharias" wrote in message
gy.net...

Arfa Daily wrote:

"Dave" wrote in message
digy.net...

I have an old Yamaha CR-820 receiver/amplifier that no longer has
any sound output. The meters still show signal strenght when a tune
across the AM/FM bands but I get no audio from the speakers or the
phone jack. No hiss. hum, carckle or pops. JUst solid dead silence.

It isn't worth sending out for a shop base repair.

Has anyone has a similar problem? Does anyone know where I can
obtain a schematic or service manual?




If it's nothing straightforward like a failed ( rather than blown )
fuse, then it's most likely that the speaker protection circuit is
operating because of a blown output stage. I've a vague recollection
that this one uses an output hybrid ( big black "IC" bolted to the
heatsink with type STK-xxx ) and if so, it is likely that this is
your problem. Some of these can be very expensive, and many of the
older ones are now obsolete and hard to obtain. If it is one of the
models that uses discrete output stages, then you might struggle to
get to the bottom of its problems, particularly without a set of
schematics, which again, might be difficult to find for an item this
old.
Arfa

The CR-820 uses discrete transistors, but the repair isn't for
newbies - there's fusible resistors inside asbestos tubing which go
bad, usually without any visible clue, and the layout is hardly
service-friendly. Mark Z.


OK, much like the modern Yammy AV amps then ...

Arfa

Well, they aren't flat packs - they're TO-3's - 2SB557 and 2SD427 IIRC.

Four-gang (once again, IIRC) tuner, all analog, silver face, wood cabinet,
rectangular metal knobs, and lots of 14 volts lead-lamps which burn out...

mark Z.



. If I run the amp with both left channel transistors out of the circuit the
right channel works fine.
I replaced a bad outout transistor after checking it. Now when I turn the
receiver on the main power fuse blows.

My guess is that the original failure took out the power transistor before
the fuse blew.



or you put something in wrong.


--
"I'm never wrong, once i thought i was, but was mistaken"
Real Programmers Do things like this.
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