[AMRadio] I hate Micamolds


CL in NC mjcal77 at yahoo.com
Sun Nov 19 18:50:43 EST 2017


Micamold caps have to be the best 'planned obsolescence' part ever made.  These caps that can fool you as they look like a common postage stamp mica, always need to be checked.  I have never found one that was not more resistor than capacitor. At least they are easy to spot as the proudly print their name somewhere on them.  They are really just a wax cap in the postage stamp looking package.  I am redoing a piece of gear full of Micamolds and purchased appropriate modern replacements.  Now, your standard low value 'real' postage stamp micas seldom give me a problem and I didn't even bother to spot check any of those.  Well, I discovered this unit has a bunch of .01 postage stamp style micas that I overlooked, and on the cap checker and ohm meter, they are leaking.... a bit.  Now these are all in circuits with only 28VDC on them, and they show 100+meg, and short on the cap checker at around 75 volts, they are supposed to be a 300volt cap.  These are all in bypass situations, no freq determining or coupling use.  What is a consensus on changing all these out?  100+meg is plenty or 100+ meg is a leaker?  100+ meg on a screen circuit to ground fed through a 47K from B+ will not load the circuit down that much, but how effective a bypass cap will it be?  Thanks for some thoughts on this.

Charlie, W4MEC in NC


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