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37-116x - audio int trans - Why did it burn out?
spfradios2
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Posts: 11
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07-08-2010, 09:02 AM
Hi all you experts...

I've been to this "phorum" before regarding my audio interstage transformer and the fact it had a burned out primary. Well, I have secured a replacement.

I'm back again because I want to learn more about how these things work. I'm asking the question... Why did the primary of the transformer burn out?

Here is my theory, tell me if I'm thinking right or wrong. The primary of the transformer is in the plate circuit of a 6F6 driver. That 6F6 has a primary grid that requires 10 volts according to the schematic and associated materials. That grid voltage is controlled by basically three resistors connected in series directly to the power supply. Referring to the schematic those resistances are R114 (330k), R108 (240k) and an IF expander pot (500k). I have found that R114 was totally open, and the pot had intermittent contact. The bottom line... the grid probably had zero volts. Would this situation have caused an uncontrolled current to flow through the plate of the 6F6 and probably burned out the transformer?

Opinions welcome.
Thanks
John Shaffer
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37-116x - audio int trans - Why did it burn out? - by spfradios2 - 07-08-2010, 09:02 AM



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