> Why guess? Why try this, try that?
I think the suggestion was to look for likely things, not
replace things at random. Better and faster to look for
likely things first.
> The logical way to troubleshoot it is to isolate it,
> easily.
> Don't assume anything, other than possibly that it is high
> voltage related.
I disagee. Like listening to an engine...you can tell an
awful lot by the sound.
> But to go head first into checking every component just
> because someone else
> had this problem once is a big waste of time. Use your
> head.
Considering a well designed amp if it is an arc that doesn't
take the HV to ground it is almost certainly not a component
that goes from HV to ground. Any arc there would dump a lot
of current until the HV went to a very low voltage.
For example?
A leaky blocky cap will normally only cause a repeated tic
if the tank has no safety choke path. The leakage will
charge the tank caps until they arc, but the high leakage
resistance limits current. As a matter of fact a **normally
working** blocking cap can cause a periodic tic of the
safety choke is open or (worse yet not installed). A bad cap
makes a bang and faults the HV to ground.
A repeated metallic or hollow sounding tic or thump is
normally caused by an open equalizing resistor on the filter
caps, or one that arcs internally.
A higher pitch buzz under load is usually something like an
open diode (again a series path that doesn't dump high
current ) but a HV transformer, once it arcs, almost never
recovers. The exception is an open lead like a bad solder
joint on the HV, but it will buzz at a 120 Hz rate....not
pop and stop.
One trick I use is a long hollow Teflon tube that can be
placed on or pointed towards components and I listen for the
noise. Of course it takes common sense and care in use.
I've seen a lot of GOOD components get changed to correct
other problems. For example I've seen blockers replaced
because the safety choke was open. I've very commonly seen
electrolytics replaced because the equalizing resistors were
off value, and the new electrolytic temporarily cured the
symptom.
I think it is actually better to listen, think, and check
the likely troublesome components first. They type of arc or
noise tells us quite a bit if we use the information
logically. That way we don't pull the oil pan, rod caps, and
valve covers only to find out is a bad alternator bushing.
73 Tom
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