Re: Troubleshooting experience and intuition


"John King" <kingsx@xxxxxxxxxx> wrote in message news:8TLPe.150$sP7.76@xxxxxxxxxxxxxxxxxxxxxxxxxxxxx
> Elvis Kabong wrote:
>
> >
> >
> > But before the following, the first thing to check
> > is the fuse value. Way too many times I see
> > 15-20 amp automotive fuses in people's amps.
> > Plus you want to test it if it is blown or not.
> >
> >
> > Ed @ Sonic Surgery
> >
>
> See... It's often the elemental things like that (fuse check)
> which I'll sometimes overlook. I'm so busy looking farther
> down the road for the 'major malfunction' that I'll get side
> tracked from the "start here, work to there" mentality.
>
> John King

Oh yeah, I've been down that long winding road
on a few occasions by taking what turned out
the nightmare route after finally deducing I simply
overlooked a *basic* shortcut right to the problem
by assuming the problem was more complex
than it turned out to be.

One time while working on an Orange amp
that had loud random arcing popping sounds,
I ignored my intitial theory and went after looking
for intermittent connections. Well, with that tiny
guage hookup wire all over that amp, I came
across lots of places with only a few strands
of wire making the connections, so I restripped
and resoldered them. That did not solve the
problem but certainly needed to be done.
The colleague who brought in the amp after
he was stumped said he thought it was an
arcing transformer and I thought that was likely,
but I proceeded looking for connection problems.
This went on for hours including cleaning sockets
and pots, sanding tube pins, tightening grounds,
replacing switching jacks that had loose contacts.

After almost giving up, I decided to *finally* try
my initial theory and measure plate & cathode
resistors and guess what? V1a's 2K plate
resistor was reading 20M! Replaced it and
that was the end of the noise - duh.

The theory was based on the sputtering
noises old Fenders make from defective
plate resistors, but I ignored that since the
noise was really loud and sounded more
like something arcing. Well, I'm sure we
all have brain farts now and then, but
sheeks! What a long way around to the
easy solution!
.

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