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tsl power transformer question

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  • tsl power transformer question

    Hi group, sorry to be such a pest. It seems like with me when it rains it pours sometimes. Over the past two weeks my two tsl went down. One was a pretty simple and a seemingly standard tsl fix the other took some time.

    The most recent one I got working still just don't seem right to me. It actually sounds ok but it still has a mild burning electronics smell (really more of a heating up smell than a burnt or burning smell). I set up both tsl's today and ran them side by side.

    Both units have brand new power tubes in them with the same tube rating from the store I bought them from. I placed both amps with the controls all in the same positions and let them heat up for about an hour a piece.

    The first unit (I will call unit A) both of its transformers feel pretty cool to the touch, the second unit (I will call unit B) the power transformer feels pretty warm to the touch (like you could easily keep your super warm on top of it.

    Both units read simular readings on the power tube pins when checking for voltages, both units have the bias set to 80mv.

    Unit A when I play it while watching the dvm on the bias pins reads around a max of 280mv max, Unit B while playing maxes out about 75mv higher or it goes up to 350mv.

    I guess if it didn't have the smell I wound't be so concerned. But it does and I just dropped a 100.00 set of winged c's in it and don't want to burn them up.

    Is there some good places and easy place without splicing wires and such to put an ampmeter in it to monitor the current? Would that be a useful test to see the condition of the transformer? This is the same unit I had some severely discolored filter caps, they are the large 330uf caps in the amp.

    Should I presume the transformer is on its way out but just hasn't gotten there yet?

    I think for now I will go down to my two older power tubes and bias at 40mv and make the appropriate connection for the speaker connection just in case it decides to take out my new power tubes.

    As always thanks for any feedback and your opinions and insite is very much appreciated.
    Last edited by wyomingrocks; 01-10-2009, 05:25 PM. Reason: one question was already answered in a prior post by myself

  • #2
    Wow

    Oh SH#t, I was looking at my amp again tonight. I put two tubes into amp
    B and set the bias and put two tubes in amp A and set the bias. Switched my speaker wire on back of the amp to the 8 ohm slot on each amp. I am running 16 ohm cabs. Hooked up my KK eq with dual outputs and turned out the lights and started watching how both amps behaved in the dark.

    I noticed amp B right on the edge of red plating. Amp A stayed pretty steady. Next I swapped tube positions on amp B and noticed the same results.

    Next I switched tubes to the other amp. Amp B still was still the problem.

    Next I swapped speaker cabs, a funny thing happened. Amp A started acting up and amp B ran pretty steady.

    I thought I had a bad speaker cable going to my cab that was giving me near red plate results. I switched cables and still had bad results.

    I measured the resistance on the cab I wired myself and it was somewhere around 14 or 15 ohms. I measured the resistance on the cab that was causing both amps to nearly redplate and it measured 3 ohms.

    I bought the cab that is measuring 3 ohms off ebay and don't use it nearly as much as I do my other cab. But maybe just maybe I am on the right track, hopefully I haven't weakened my transformer.

    I guess the moral to this story is never trust anything to be what is says. I never thought twice about measuring my cab's resistance. It is a good looking cab and I had no reason to question it not being 16 ohms like stated. I am really interested now to see how it is wired. That is all I have for now, just thought I would share my journey with you.

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    • #3
      Look in the "3 ohm" cab, and see if the speakers are 16 ohms or 4 ohms. Four 16 ohm drivers wires in series/parallel results in a 16 ohm cab, but someone could have rewired them in parallel for a 4 o0hm total., which would read about 3 ohms on a meter.
      Education is what you're left with after you have forgotten what you have learned.

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