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Originally Posted by madmike17
I wonder if I installed it backwards last time?
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It's doubtful the vib could be installed backward. But if the supply voltage to the radio is the wrong polarity, the filter caps will also get reversed polarity. This is true only with synchronous vibrators, not with radios using tube rectifiers (0Z4, 6X5 etc.). With tubes, the supply polarity doesn't make any difference.
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It ran for about a minute, and faint crackles came through the speaker, but no sound. Then the 10 mfd cap let out its guts.
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If the 10mfd cap you're referring to is C34, it's right on the main B+ line from the transformer, and it would definitely 'let out its guts' under reverse ("B minus") polarity. Two more caps 'downstream' from it, C29a and C29b, would also get seriously cooked (unless C34 dead-shorted and spared them that fate).
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I couldnt find a reason, I just figured it was defective.
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It sure sounds like reverse supply polarity. Had you installed it in a car when this happened, or when you had it on the bench?
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I also later found out that the audio interstage transformer was bad. If it is just the contacts, would a little filing help? Ill try to find a scope if I can.
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If the audio interstage transformer open, or what?
The vibrator contacts might still be OK if you didn't run it that way too long.