On Wed, 2007-10-31 at 11:18 -0700, Jim Brown K9YC wrote:
> I just got off the phone with the guy at Ten Tec who works on the
> Titan 425's.
>
> I asked him about replacing all the caps if one is bad, which
> someone here or on another list had said was necessary. He said no,
> that is NOT necessary. Simply watch the plate voltage, and if you
> see it dropping, or if you get reports of hum, look for another bad
> cap and replace it.
>
<SNIP>
> 73,
>
> Jim Brown K9YC
>
It certainly is cheaper to replace each capacitor in a series string as
it fails, but sometimes electrolytic capacitor failure is explosive
filling the cabinet with shredded foil and conductive electrolyte filled
crepe paper. Since a group of electrolytics probably were originally
closely related and have experienced the same circuit and environmental
stresses, I'd consider that when one failed the rest were near to
failure from the same history. So I'd replace them all.
Be sure that the voltage balance resistors are pretty closely matched in
value because their match sets the voltage equality on the capacitors.
It could be that the capacitor that failed first had a higher voltage
applied.
73, Jerry, K0CQ
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