wrote in message
...
On Fri, 4 Dec 2015 06:49:10 +1100, Trevor Wilson
wrote:

On 3/12/2015 11:34 PM, Mark Zacharias wrote:
OK, so it appears there is very little to discuss on this group in areas
like repairing audio components, amps, receivers, power supplies, etc
these days.

I "tune in" here almost daily and rarely find anything of interest to
me.

Maybe we could share some "war stories" of cool repairs we have done in
the past.

Re-live some past glories?

The first time you traced down a bad reset line for a microprocessor?

That integrated amp that blew a channel about once a year until you
caught that bias diode occasionally opening up?

Sansui 5000A's? (yuck)

Crappy Euro caps in Tandberg tape decks?

Those times you sweated whether you could even get this thing put back
together?

Any more recent successs stories to brag about?

C'mon, don't we all enjoy patting ourselves on the back, really?


Mark Z.

**I recall the first time (1980-ish) I discovered those fusible
resistors that go high after a few years. With no obvious signs of
distress. Now I just head straight for the buggers.

Then there's those low value (/=47 Ohms), 1/4W cracked carbon resistors
that go O/C when subjected to ca. 60+ Volts with no signs of burning
(Marantz 1200b, 240, 250M, 500 models). Over the years, I learned to
suspect any resistor over the value of 100k, if the circuit is
displaying some kind of mysterious fault that cannot be explained by a
semiconductor failure or cap leakage.
That resistor story is interesting. About two years ago I had a linear
power supply fail in one of my CNC machines. I did the troubleshooting
bit and discovered a bad -15 volt regulator. So I replaced it and then
a few weeks later something else went bad and I couldn't find it. I
took it to a friend who is an electronics engineer and he discovered
an open resistor. I asked why he checked it because there was no
visual reason for it to be bad. It wasn't cracked or discolored. He
said that's what he usually did first, check for open resistors. He
said it was a common fault. Since then the power supply has been
operating fine.
Eric



Yeah - when "the usual suspects" don't pan out, I start looking for bad high
value resistors.

Had a bad 150K 1/8 watt carbon on a late model Pioneer surround receiver the
other day.


Mark Z.