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Traynor TS120B bass amp

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  • Traynor TS120B bass amp

    hi all
    I have a traynor bass amp TS120B I am trying to repair
    The amp powers up ok but the output is garbled mixed with 60 cycle hum
    The xlr output from preamp alone is distorted and hums
    I replaced TL071 and TL072 in preamp
    there is a switching IC TL604 that i did not change as I could not locate one to purchase
    Transformer output is 36 volts AC steady
    The amp rails should be 50 volts + and -
    however the test on the output of the bridge rectifier gives me plus 50 volts
    and minus 32 volts
    I changed the rectifier but the readings are unaffected
    Output Transistors were removed and ohm meter tested and seemed to check out correctly
    I think this is a preamp problem but not certain of that
    however I am puzzled at the low minus voltage reading at the negative rectifier output
    any thoughts on a possible cause for the amplifier problem or cures ?

    thank you in advance

    regards
    robgrif
    Attached Files

  • #2
    The filter cap for the -50V is probably bad. Otherwise something is loading down the -50 supply. If you measure AC at the outputs of the rectifier you will probably see much more AC on the -50 than on the +50 side.
    Originally posted by Enzo
    I have a sign in my shop that says, "Never think up reasons not to check something."


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    • #3
      traynor ts120b bass amp

      Originally posted by g-one View Post
      The filter cap for the -50V is probably bad. Otherwise something is loading down the -50 supply. If you measure AC at the outputs of the rectifier you will probably see much more AC on the -50 than on the +50 side.
      thanks for the tip you were right on the mark
      replaced the cap and amp came back to life
      voltages now are correct
      thank you for help
      regards
      robgrif

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