"Mark D. Zacharias" wrote in message
et...
Arfa Daily wrote:
"Mark D. Zacharias" wrote in message
. net...
Arfa Daily wrote:
"Dave" wrote in message
. 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.

I was being facetious Mark, and referring to the fact that it's layout is
not very service friendly ...I went to a Yammy training seminar recently,
and the national service manager told us that the average turnaround time on
an AV amp for a Yammy dealer, was 22 days, which was really too long, and
could anyone venture a suggestion as to why this was. I told him that the
first 16 days were spent looking at it sitting on the shelf, hoping that it
would go away. The next 3 were spent trying to work out what the internal
diagnostics were trying to tell you. The next 1 was spent trying to strip it
apart and work out which screw was still holding it. The next day was spent
fixing it and putting it back together, and the final day was spent either
rejoicing that you could write a bill out for it, or crying whilst watching
all the magic smoke being released again ...!! Sound about right ? d;~}

Arfa