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Power Transformer oddity

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  • Power Transformer oddity

    I built a 6G15 last year and the PT has a 240-0-240 HT with a 6.3V heater winding. Well last weekend I changed the reverb tranny in it to see what difference it made, and that's another story (sounds quieter because of the end covers BTW).

    But in changing over the RT, I inadvertently created a short from the B+ to the chassis ground (from an overly-long RT primary wire poking through the CLC output filter eyelet - DANG!), and when I switched the amp on there was a slight humming noise for a couple of seconds followed by light wisps of smoke and the sound of a faint crackling noise, and I immediately realised what I'd done and switched it off.

    I pulled it apart, and found the miscreant wires poking out the back of the main board and clipped it off, stuck it back together and fired it up and it works okay - because somehow amazingly I think I must've caught it in time (or am I fooling myself?).

    Anyway I ran it last night for 4 hours at band practice no problems. Today I measured the VAC out of curiosity and it was higher than what I thought it should've been (pretty evenly 260-0-260 - as opposed to 240-0-240 that I thought I had ordered when I got it last year). The whole thing is SS/diode rectified and the B+ is 350VDC at idle (which is about 17V less than I thought it would be with that 260-0-260VAC on the HT).

    Anyway I'm just curious if anyone else has nearly stuffed a PT in this way but managed to avoid it so to speak?
    Building a better world (one tube amp at a time)

    "I have never had to invoke a formula to fight oscillation in a guitar amp."- Enzo

  • #2
    Yes. I have done that and afterwords the amp kept working. Your voltages are acually very clos to spec and IMHO the "differences" could easily be caused by normal tolerances and line voltage variations.
    Cheers,
    Tom

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