Re: TOT: Capacitors

In article <VA.00000179.036361df@xxxxxxxxxxxxxxxxxxxxxx>, Roderick
Stewart <escapetime@xxxxxxxxxxxxxxxxxxxxxx> scribeth thus
In article <pan.2007.10.18.17.44.30.4384@xxxxxxxxxxxxx>, Paul Sherwin wrote:
All of them? Why do you think you need to replace all of them?
 
What you are saying sounds a bit like "I need to replace all the nuts 
and bolts in my car because I think one of them is a bit loose and I 
don't know which one".

Rod, those of us who work with old valve equipment have learned the hard
way that practically all consumer grade waxed paper capacitors from
the 1950s leak. It's very difficult to test them because they often only
leak at high voltages and usually must be removed from the circuit for
testing. Multiple leaky caps can produce all sorts of strange symptoms, so
it's standard practice to replace *all* wax caps of 1nF or larger as the
first step in a restoration unless they are of a type known to last well.

If you say so, but it still sounds a bit drastic to me. I guess I'm just
old-fashioned, having been educated in the school of thought that believes
that repair consists of identifying and replacing the components that are
actually faulty and leaving the rest alone. I would never replace components
preemptively unless the consequences of not doing so were worse, but the
preemptive replacement of *all* the capacitors in an amplifier would be a
huge undertaking, and in old equipment would stand a good chance of
disturbing something else and causing more trouble than it cured, especially
if you don't know the difference between a microfarad and a nanofarad.

Rod.


With older stuff sometimes resistors drift in value electros are always
worth replacing and some makes of Capacitor very much so!, especially
polythene which ages over a long period. Its not removing authenticity
at all.

I refurbed a QUAD 33/303 for the wife a couple if years ago, new caps in
the power amp some sealed cermet trimmers and beefed up a couple of bits
of wire. It was some 28 years old then and I reckon it will be good for
another 20 or more!....
--
Tony Sayer



.

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