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Samson TXM20 schematic

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  • #1

    Samson TXM20 schematic

    Hello folks,
    Am deep into a Samson TXM20 power stage rebuild. We've rebuilt one channel & are now getting weird offset & general improper operation.

    The board isn't set up very intuitively, so it's difficult to determine what transistor does what or which transistors are in which power amp as well as having some resisotors that are burned & unidentifiable. The other channel doesn't seem to mirror this one to help determine what these resistors are.

    Does anyone have a schemo for this power stage? Thanx, glen
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  • #2
    Don;t have that one in my files. Did you contact Samson in NY? They are usually forthcoming.
    Education is what you're left with after you have forgotten what you have learned.

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    • #3
      Hello Enzo,
      I actually did e-mail Samson & was delighted at the quick response. I had the files within 1hr.

      One of my techs who is a bit hard-headed, fought this thing on & off for a few days w/o a schemo and actually did very well (imagine that, a hard-headed tech!!). He finally asked me to find one after much dain-brammich. I took over the repair as he was on vaca & got the last problem fixed in 15 minutes, aside from what you have to do to get this thing apart.

      He had everything bad replaced but one 47ohm fusible resistor feeding from the bias ckt to the drivers. And then to add insult to injury, the speaker relay was fused open!

      This amp is designed a lot like the Yorkvilles are where they have a half a million little support transistors & fusible resistors all over the place. Finding them all is sometimes a bit of a challenge.

      Don't know if you've ever had the 'pleasure' of working on one of these things. They are set up in a fashion where you have to remove about 20 screws on the heatsink forthe power transistors & drivers to get the board off of the heatsink. That is the only way to get under the board. What a stupid design.

      This also has the stepper power supply switched by 2 mosfet IFR transistors. You have to test for that proper operation, also.

      What happened to the days of the simple brute force Peavey CS600's! One power transistor blows & that's ALL that blows.

      Anyway, it's all fixed & happy now. Thanx, glen

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