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gil wrote:
I always heard about leaky caps being a problem with boatanchors, other than checking for the capacitor value is there a way to check if its a "leaky cap" using just a multitester or voltmeter? Thanks.....gil There's some good capacitor testers around but as a rule on older BAs (30s-40s) if it doesn't pass an ohmmeter test you need not go any further. I chuck anything over about 1 Meg of leakage which tends to be most all wax/paper caps from that era. The digital voltmeters often have a capacitance test function but are thrown off in the presence of leakage. Again, if it doesn't measure right, out she goes. The problem is due to the breakdown of the paper dielectric inside. For the most part thats inevitable in spite of how well sealed it is. Some of the high-end mil-spec metal cased guys have survived but thats about all. The rest are hit-and-miss. In later gear, say the 50s, the "good" rate is much improved but certain types like the banded black beauties are notoriously bad as are those pink plastic ones found in 50s/60s Hallicrafters gear. The debate lingers on just how much performance degradation and reliability can be tolerated since the bad caps may not have a particular detrimental effect *today* depending on where in the circuit they are used. I suppose it depends whether or not you are "restoring" or "repairing". I cross-posted this to rec.antiques.radio+phono so you could catch some other opinions. Good luck! -Bill |
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