Silverface Champ amp has a short

Discussion in 'Amp Tech Center' started by rockman627, Jun 6, 2021.

  1. rockman627

    rockman627 TDPRI Member

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    "So, we have shorts in the yellow and green wires of the PT, and a 2700 ohm resistor that is now 49.6 ohms. Seems to me there could also be problems with the output transformer (Weber W022905).I unsoldered the wires and I'm reading 350 ohms between blue and red (primary) and .5 ohms between green and black (secondary). I'd say the 49 ohm resistor took out both transformers."

    What do you think of the rest of my estimate?
     

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  2. Lowerleftcoast

    Lowerleftcoast Friend of Leo's

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    The 350R is about right. The secondary on mine is 1R. It may be in the ballpark.

    Do you have a low voltage AC source to put through the coil? A variac or an AC wall wort?

    You can test with the wall voltage but I am more comfortable with a lower voltage.
     
  3. Lowerleftcoast

    Lowerleftcoast Friend of Leo's

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    The 2.7K resistor is the NFB resistor. It should not be able to damage a transformer. It is possible it could be a victim of a catastrophic event. I don't know of a scenario where it would cause a problem.
     
  4. Lowerleftcoast

    Lowerleftcoast Friend of Leo's

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    Are you measuring the 2.7K resistor in the circuit? It would have to have one leg lifted to get an accurate measurement. Otherwise it would read close to 47R.
     
  5. rockman627

    rockman627 TDPRI Member

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    I forgot you have to lift one side to read Ohms.
     
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  6. rockman627

    rockman627 TDPRI Member

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    Thanks to all of your for your help in this. As I previously mentioned, this is my first time troubleshooting transformers and heater circuits and I would have made a few wrong decisions if not for the advice you guys shared. I'll tell my buddy about replacing the PT and will try to convince him to at least replace some components, maybe even the circuit board.
     
  7. Roger66

    Roger66 Tele-Meister

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    Did you ever find out what was wrong with your Champ??
     
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