CJ
Well-known member
burn thru was a few layers deep, i should have taken an ohm meter reading from pri to sec to see if there was a short, if there was a short from pri to sec it probably would have fried the speaker unless the speaker was not grounded on one side, or all the energy could have gone to ground via the xfmr sec start since the black lead was nearest to the pri bar b que. a short to a grounded sec could explain the drop in B+ but the pwr trans would have got hot in a hurry, the rect tube fried or the fuse blown,
another thought is the partial layer on the pri finish formed a tuned circuit with the positive F/B osc. although this is a long shot,
the pri-sec insl was a couple layers of 0.002" paper, something like 10 Nomex or Kapton would have prevented the melt down. Or at least a couple of layers of 5 KP,
Measured ratio was about 31 to 1, maybe skewed from the cooked coil. I did not count the pri turns, the wire measured 0.005",
the core was 625 EI (5/8" tongue), the stack was about 0.530"
Full props to Potato Cakes for sending this gut.
another thought is the partial layer on the pri finish formed a tuned circuit with the positive F/B osc. although this is a long shot,
the pri-sec insl was a couple layers of 0.002" paper, something like 10 Nomex or Kapton would have prevented the melt down. Or at least a couple of layers of 5 KP,
Measured ratio was about 31 to 1, maybe skewed from the cooked coil. I did not count the pri turns, the wire measured 0.005",
the core was 625 EI (5/8" tongue), the stack was about 0.530"
Full props to Potato Cakes for sending this gut.
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