[R-390] Filter cap temperature

[Roy Morgan]

At 09:36 AM 5/6/2005, you wrote:
>While tinkering with the "new" R390A last night, I noticed that C603 is
>getting slightly warm.  The other cap is cold.  Is this possible an
>indication of low ESR?

Barry,

Most likely that cap is leaking more than it should.

"ESR" stands for Effective Series Resistance. A capacitor behaves as if it 
has an ideal capacitor in series with a resistance.  I good cap will have 
low ESR.  A cap designed for switching power supply duty where the ac 
current through the cap is very high, will have an even lower ESR.

If C603 is the first one after the rectifiers, then it will have 
experienced higher ac ripple all it's life and may be tired by now.

>  Do these old caps generally leak a bit or should I
>be concerned?

Many of them leak. If they are leaking, you should be concerned.

>  I hadn't planned on replacing them as they seem to be
>working, but if they're going to blow, then I'd rather go ahead and
>replace/rebuild them.

Try rebuilding the one that gets hot first.  Measure the leakage on it first.

Roy



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