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Thread: Speaker and OT question

  1. #1
    Join Date
    Nov 2016
    Nova Scotia

    Speaker and OT question

    I did a little looking before I posted this, but it's a hard thing to search for, so here's a quick question.

    A couple of weeks ago, I built a little EL84 push-pull head which I'm really enjoying. When I'm feeling too lazy to pull out my 1 x 15 cab, I've been using a cable connected directly to the extra pair of quick-connects on the speaker of a 1 x 12 combo, and disconnecting the speaker cable to the amp chassis. The other night a friend came by and we were playing around with both amps. I realised later that when I plugged the head in, I forgot to unplug the the other cable. Later when playing the combo, I heard a couple of cracks. It may well have just been the jack on the guitar cutting out, but is there the possibility of having damaged the output transformer? The OT secondary would have been connected in parallel with the speaker, and so would have had some portion of ten or so watts through it. The primary at the time would have been at 0 VDC as it was not powered up.

    I think it's probably fine, but some reassurance from those with a better understanding would be great.


  2. #2
    "Thermionic Apocalypse" -JT nickb's Avatar
    Join Date
    Dec 2009
    Devon, UK
    Probably no harm done as the voltage developed on the primary is likely in the normal operating range ( other than a minus B+ DC offset).
    pdf64 likes this.
    Experience is something you get, just after you really needed it.

  3. #3
    Old Timer J M Fahey's Avatar
    Join Date
    Oct 2007
    Buenos Aires, Argentina
    If it works, it works.
    Donīt overthink it.
    Juan Manuel Fahey

  4. #4
    Join Date
    Nov 2016
    Nova Scotia
    Thanks guys, I'll give it a try later. It was probably just the guitar making some noises.

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