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William Sommerwerck
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 Posted: Thu Oct 09, 2008 5:12 pm Post subject: JVC XP-A1000 redux |
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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. |
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Franc Zabkar
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| Posted: Fri Oct 10, 2008 1:32 am Post subject: Re: JVC XP-A1000 redux |
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On Thu, 9 Oct 2008 05:12:04 -0700, "William Sommerwerck"
<grizzledgeezer@comcast.net> put finger to keyboard and composed:
[quote]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.
[/quote]
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. |
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William Sommerwerck
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| Posted: Fri Oct 10, 2008 5:36 am Post subject: Re: JVC XP-A1000 redux |
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"Franc Zabkar" <fzabkar@iinternode.on.net> wrote in message
news:raqse49dflt50f5otde2ujh97s3037mtal@4ax.com...
[quote]On Thu, 9 Oct 2008 05:12:04 -0700, "William Sommerwerck"
grizzledgeezer@comcast.net> 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?
[/quote]
They could, but...?
[quote]Of course a brain-dead uP could itself be the result of a missing or
low supply rail, or a faulty crystal.
[/quote]
True. Guess I won>t know until I tear into it over the weekend. |
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