Since I posted my original question about the failure of my JVC hall
synthesizer...


Several years ago, when I turned it on after a long period of disuse, the
VF
display was scrambled and the unit didn't work. I let it "cook" for a
day,
and the (apparently) malformed cap that was causing the problem decided
to
behave itself.

Several weeks ago, I finally got my rear amplifiers, so the JVC was
restored
to full-time service, and was working magnificently, until... You guessed
it.

About a half-hour ago, the display went dead and the outputs turned into
a
not-too-loud digital "buzz". The input is locked at "digital". (The
default
is analog, and you have to manually switch.)

My guess -- and this is only a guess -- is that this a power supply
problem.
(The fact that all the channels went out does not automatically eliminate
any of the LSIs, unfortunately.) I have the service manual, but before I
start ordering mass quantities of electronics (or even start checking
voltages), I'd like to know if anyone has any views.

Please note that I don't expect anyone to diagnose what might be a messy
problem from a distance. (I'll call JVC tomorrow, anyway.) I just wanted
opinions.


....I've done some more checking. I found that if I let the unit sit
overnight, it comes on again -- then fails after a few minutes. I've been
able to repeat this.

This suggests some component is failing then reviving. (Duh...) As the
symptoms -- dead display, input locked to digital source, low-level buzz at
all outputs -- are not likely to be caused by the failure of a single chip,
the likelihood of something in the power supply -- in this case a bad cap
that "comes and goes" -- seems likely.

Any thoughts?

Thank you.

On Thu, 9 Oct 2008 05:12:04 -0700, "William Sommerwerck"
put finger to keyboard and composed:

As the
symptoms -- dead display, input locked to digital source, low-level buzz at
all outputs -- are not likely to be caused by the failure of a single chip,
the likelihood of something in the power supply -- in this case a bad cap
that "comes and goes" -- seems likely.

Why couldn't all those symptoms be the result of a brain-dead uP?

Of course a brain-dead uP could itself be the result of a missing or
low supply rail, or a faulty crystal.

- Franc Zabkar
--
Please remove one 'i' from my address when replying by email.

"Franc Zabkar" wrote in message
...
On Thu, 9 Oct 2008 05:12:04 -0700, "William Sommerwerck"
put finger to keyboard and composed:

As the
symptoms -- dead display, input locked to digital source, low-level buzz
at
all outputs -- are not likely to be caused by the failure of a single
chip,
the likelihood of something in the power supply -- in this case a bad cap
that "comes and goes" -- seems likely.

Why couldn't all those symptoms be the result of a brain-dead uP?

They could, but...?


Of course a brain-dead uP could itself be the result of a missing or
low supply rail, or a faulty crystal.

True. Guess I won't know until I tear into it over the weekend.