Re: Yamaha CR-820 Repair: No Output, Tuner shows signal received.




"Mark D. Zacharias" <spammenot@xxxxxxxxxxxx> wrote in message
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Arfa Daily wrote:
"Mark D. Zacharias" <spammenot@xxxxxxxxxxxx> wrote in message
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Arfa Daily wrote:
"Mark D. Zacharias" <spammenot@xxxxxxxxxxxx> wrote in message
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Arfa Daily wrote:
"Dave" <rjtechnology@xxxxxxxxx> 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


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