Re: Yamaha RX-V995 Surround Sound Receiver shuts down...

Mark,

This is my Cousins amp, I've been in the repair business for over 30+
years. If it has a wire coming out of it I will at least look at it.
I work on TV's that have tons of built in diagnostics; the days of
trim pots seem to be gone. I really appreciate your help.
Speaker testing>>>
I thought of that and ran over at his house last week with my
ohmmeter, all lines were in the 3ohm range. This is using a Fluke
digital VOM. I do have an impedeance meter that I could dig out to do
some testing on the speakers didn't take it with me. I thought that
one of his cats might of bit through the wiring. I ran the wires with
my hand and found nothing of note wrong with the wires jackets. Due
to the age of the unit and finding that mem cap leaking I could only
think that, perhaps, there is some leaky i.e. 10uf@50V cap in the
power amps pre driver section pulling the DC offset up. Is there some
sort of built in Diags? He couldn't find the manual; however, I
haven't seen any owners manuals have too much in the way of technical
information. Sometimes too much info for the average consumer is
dangerous. I get VCRs in that the user opened up to try to fix it and
frankly I would rather turn those ones down.

I looked at all the boards for cracks and they really look clean. I
blew out all of the dust so that I could get a good look at them, for
the age of the unit it really is clean. He has it mounted in a
cabinet that has a glass door on the front of it.

Thanks again for the reply,


Markus

On Fri, 09 Sep 2005 10:34:18 GMT, "Mark D. Zacharias"
<spammenot@xxxxxxxxxxxx> wrote:

>
>"Markus" <mporter@xxxxxxxxxx> wrote in message
>news:iig1i15h7t7c85c7uqb5lkdprgivevor18@xxxxxxxxxx
>> Greetings,
>>
>> I have a Yamaha RX-V995 Amplifier that, at any given time, will just
>> shut off. All I have to do is power it back on and sometimes it will
>> work for hours and other times it will shut off right away. It would
>> not hold the last settings and I found the memory cap to be defective,
>> you know, leaky cap syndrome. That was a 4.7F 5.5V cap. at any rate,
>> I went over it with a fine tooth comb looking for loose solder joints
>> and other caps that might be leaky, found and re-soldered a few
>> cracked joints on a regulator board buried in the bottom of this
>> beast, all else looks fine. It does have some power relays for the
>> speaker outputs and B+ power. I remember replacing those on the
>> fisher amps years ago... I was wondering if anyone has worked on one
>> of these and what you might of found. This unit is loaded and looks
>> clean sadly; I do not have a schematic. Nothing leaked into it from
>> the top. It doesn't appear to have smoked any transistors or
>> resistors, at least none of the major 'let the smoke out' components.
>> The power to the proc seems steady and there isn't any noticeable
>> ripple on any of the power buss lines that I have found. I really
>> haven't checked for DC showing up on the outputs as of yet, not really
>> sure how the safety circuits work in this unit. It doesn't run too hot
>> when on for hours at a time. I thought finding and replacing the 4.7F
>> cap would have taken care of it, but still shuts down. To reply to me
>> directly just take caps out of my address.
>>
>> Thanks in advance,
>>
>> Markus
>> mporterNOSPAM@xxxxxxxxxx
>
>The nature of this failure suggests to me that there is a speaker wire
>shorting intermittently.
>
>Yamaha's have diagnostics built in that can tell us whether it was an
>over-current (shorted speaker wire) situation, a DC offset problem on an amp
>channel, a power supply problem, etc.
>
>You may e-mail me direct if you would like some help with this; I am an
>authorized Yamaha servicer.
>
>email to:
>
>mzacharias@xxxxxxxxxxxxx
>
>and reverse the domain name.
>
>Mark Z.
>

.

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