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Sunn Beta Lead Output transistors

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  • Sunn Beta Lead Output transistors

    Hello folks,
    I have a Sunn Beta Lead circa 1970's. I have decided to use the Mot MJ15003 & 4 power transistors but wonder if these amps are like the older ones where the original output transistors were fundamentally low frequency response that the designers did not have to design in snubber caps to prevent oscillations. Epitaxial vs whatever they were back then.
    So does anyone know if there will be oscillation issues on this era amp? Been a while since I've worked on the Acoustics & Sunn amps...Thanx, Glen Whatley Mars Amp Repair

  • #2
    Howdy, Glen.
    Here is the service manual.
    Beta Series Service Manual.zip
    I am not a guru but I see nothing esoteric in the circuit that would require tweaking.

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    • #3
      Thanx Jazz. I just know that the original 2Nxxx type transistors from 60's - 70's had much lower frequency response compared to the latter epitaxial ones, so the MFG'S didn't have to be concerned about parasitic oscillations at the higher frequencies as they did later (part of the reason you see all those PF value disc caps all over the place in the later amps).
      I recall working on an older Trace Elliott that i had to add snubber caps on the outputs to stop the oscillations.
      Thanx for the schemo. Much better than the one i have.

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