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

Sound
about right ? d;~}

Absolutely. I just got in an RX-Z9, lightning struck. Can't tell you
how much I'm looking forward to that one...

Mark Z.

Hey Mark

Have you done much with the RX-Z1/DSP-AZ1 ? Have you had any problems
with the 4 pin 5v regs? I've got one in at the moment. Runs
absolutely fine for about 20 mins, then starts cutting out, back to
standby. Re-powers with standby switch, but about 1 second only.
Diagnostic memory says PS Prot : 016 K/L and then some stuff
referring to the processor rev numbers. Don't know about you, but I
have a hard time ever making any sense out of those Yammy diag
messages. " PS " rather than " DC " says power supply rather than
output offset protect, but what is " 016 " trying to tell me ? I
seem to recall that it refers to a percentage error on a rail, but
that there are two different schemes used for the reference. Today, I
went down the path of pulling out the sub psu board to the point
where I could get at it to take some measurements on all the regs on
there. With the meter on peak hold, I caught the output of IC451
going up to 8.54v just before it tripped out. Now I reckon that's
about 160% up on the correct 5v, so is that what " 016 " is trying to
say ? Interested as to whether you have had anything similar. I've
got a replacement coming tomorrow, so should know within 20 minutes
of turn on, but already, no matter what I charge for the repair, I'm
actually going to be down when you count in all the time to
dismantle, trouble shoot, and reassemble. Without doubt, I'd have to
say that Yammies are among the worst of the current crop of AV amps
for service and repair. They are just not friendly at all in any area
- electronic design, mechanical design and user interface.
Arfa

I have had that exact problem on one - and the regulator fixed it just
fine - no other damage done.

I've never bothered to try to decipher those DC error levels. They are
based on 5 volts, as I recall.

Mark Z.

OK, well that's good to know. The reg didn't actually turn up today, so
hopefully tomorrow. You are right that the error figures do relate to 5v - I
can remember the little Japanese guy that lectured me on it originally,
saying so, but his english was not too good, and I was having enough trouble
just trying to stay with that, let alone the in-depth meaning of what he was
actually saying. I definitely do remember him saying that there were two
different schemes as to how the figure related to 5v though. Shame really,
as he was a very clever guy, and clearly knew these beasts inside out, but
boy, was his lecture hard work to understand, just purely from the
linguistic point of view.

And then, of course, we had Mr Beardy in the class, who stopped the poor
little guy every six sentences, and took him, and the whole class, off on a
tangent about some obscure problem that he'd had 10 years ago, for 15
minutes. I'm sure that you've been there ...

Thanks for confirming my suspicions about the 5v reg - I'll let you know !

Arfa