[time-nuts] Replacing electrolytics - any disadvantages of high temp ones?

Will Matney xformer at citynet.net
Fri Jun 24 20:56:27 UTC 2011


Speaking of replacing electrolytic capacitors, which I am now doing on a
Fluke 845A, I found a carbon comp resistor way out of spec. It is a 150
ohm, 1/4 watt current limiter, for a 10 Vdc zener. I noticed that it had
looked to have been hot (or gave off excessive heat), and had made a shiny
place on the PC board above it, though the resistor doesn't show any burnt
color. When I measured it, it was reading around 1 to 2 ohms. The zener was
still good, luckily, as was the bridge rectifiers, and filter cap (though
bulged), and this is the supply voltage for the switching transistors,
which run the chopper transformer.

My question is, have any of you seen a 150 ohm carbon comp resistor change
that much in value? I wouldn't think they could, but evidently, this one
did, and if so, I wonder about the others in the meter.



*********** REPLY SEPARATOR  ***********

On 6/24/2011 at 11:22 AM Brooke Clarke wrote:

>Hi Chad:
>Google found it:
>But it's not that informative.
>The best info I've seen on measuring components is the HP (Agilent) 
>Impedance Handbook.
>I measured dozens of caps using a number of different methods to see how 
>well the combined ESR and Capacitance meter I sell works.
>Does anyone know of a modern cap leakage tester?
>Have Fun,
>Brooke Clarke
>GMail / AnalogAficionado wrote:
>> Cyril Bateman called Understanding Capacitors
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