PT and OT for 1971 Marshall Super Tremolo 100 watt

Discussion in 'The Workbench' started by mdc1, Jul 30, 2020.

  1. mdc1

    mdc1 New Member

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    Hi

    Anyone know what replacement transformers I need for PT and OT for this amplifier head?
    standup transformers, but I do not see much in terms of identification.
     
  2. Chris-in-LA

    Chris-in-LA Well-Known Member

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    You need both transformers? @neikeel might be able to help direct you to replacement parts or the specs if that helps. Are you restoring a basket case or something?
     
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  3. neikeel

    neikeel Well-Known Member

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    In 1971 Marshall used either Dagnall or Drake for their transformers
    The Dagnalls would be a C2668 OT and T2562 PT (or T3556 came in early 70s)
    The Drakes would be 1202-99 OT and 1209-3 (these are rarer).
    You have a choice of Marstran, Merren or Classic Tone for these equivalents
    I would go with Marstran and Merren joint first and Classic tone a close second.
     
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  4. American Viking

    American Viking Well-Known Member

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    Have the old ones been tested? I'm surprised both transformers would need replacement at the same time. It would be best to keep stock iron in an amplifier from 1971.

    Sight unseen I would bet the electrolytics are bad and causing the amp to be inoperable unless some catastrophic failure occurred and took out the OT and PT at the same time. I am making a big assumption here simply based off what you are asking for.

    The 1959T amplifiers if I recall correctly use PT's with only two secondary coils. One for B+ and the other for heater wires. The bias voltage is taken off the B+ coil. You can use a transformer for a later model 1959 amp as well if you modify the wiring to take the bias from a separate coil as the later transformers will have three secondary coils for bias voltage, B+ and heaters.

    You can use a 40-18068 from Classic Tone for the PT and 40-18067 for the OT. I only listed these numbers as I'm not as familiar with the Marstran or Merren stuff but I would trust the recommendation to try them as well.

    I would go through the amplifier to verify that these would work correctly. Again, I am making this assumption sight unseen. If this amp has more than two secondary coils than you will need a different PT to work as a drop-in replacement.
     
  5. neikeel

    neikeel Well-Known Member

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    The 1959T followed the same PT arrangements as the normal 100w 1959 and 1992s (or for that matter the PAs. So the earliest 45/100 with Drake 1203-43 PT took its bias feed off half the HT feeds you see these with 150k bias droppers the 1203-80 amps used 33k or 27k bias feed droppers. The subsequent models with T2562 etc all had bias taps of 90v these you see with 27k bias droppers.

    American Vikings points are all valid, but without more info from the OP we are all kind of shooting in the dark.
     
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