Burnt resistor m15mk1

    This site uses cookies. By continuing to browse this site, you are agreeing to our Cookie Policy.

    • Burnt resistor m15mk1

      A couple of months ago i bought this kit and i had a problem with some smoking parts..
      I wasn't able to resolve the issue so i ordered new parts (all new resistors, pots, caps, boards).


      But now the R23 started smoking/ burning
      And when in standby the yellow wire at the standby-switch starts smoking/sparkling.
      So i thought the power transformer was broken but all the voltages at the pins of the OT are right.

      Maybe somebody has an idea what could be wrong?
    • May be you know (and like?) this verse of a Neil Young song (Powderfinger):
      "Red means run, son, numbers add on to nothing"

      But if you don't like numbers (e. g. measured values of parts or voltages) the only option that remains is to run (from your burning amp).

      R23 lays (nearly) at the beginning of the R-C supply chain of the amp. Behind this resistor two smoothing caps and six(!) tube stages are connected to the B+ voltage.
      To find the error you have to cut all six connections to the tube anodes and the two smooting caps and then reconnect them from start to end.
      In each step you have to survey the current through R23 by measuring its voltage.
      Under normal condions (all stages connected and no errror) that is 289 V - 267 V = 31 V! (damn, that are numbers).
      BTW: What is the value of the mounted - and well smoked - R23?.
      If in a process step the voltage on R23 rises above 31 V, you found the region of error.

      If you are not trained and experienced in working and measuring on equipment with high voltages leave this work to an expert - that costs money but not your life!


      Regards
      Bernd