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Old 29th March 2005, 02:45 AM   #1
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Default OPT failure modes

I have a scavenged PP OPT that is bad. It's symptoms are that the center tap to either plate connection measures open. However the center tap to either screen tap measures correctly (like the other good OPT.) Seems like a loose connection at the center tap could be the problem, but I'm not knowledgeable on how to interpret this based on the likely winding arrangement.

Any suggestions or comments are appreciated.

Thanks!
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Old 29th March 2005, 04:26 AM   #2
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And plate to UL is open as well, right?

Sounds to me your taps (not the CT) are dead. You can take it apart and hope to fix it, or use the UL taps as-is. You'll get what, about 1/4 primary impedance? Might work for some low voltage high current tubes... 6W6 or a sweep perhaps?

Tim
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Old 29th March 2005, 05:38 AM   #3
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Quote:
Originally posted by Sch3mat1c
And plate to UL is open as well, right?

Sounds to me your taps (not the CT) are dead. You can take it apart and hope to fix it, or use the UL taps as-is.
Yes. Plate to UL open.

Too bad it's potted. Unless the wires are burnt near the external connections there is no hope of fixing. Bummer.
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Old 29th March 2005, 11:59 AM   #4
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It's curious (though not impossible) that the primary is burnt out at the same spot on both sides of the CT. It would definitely be worth doing whatever digging you can through the potting material to check the winding termination.
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