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  • Tubeworks schem?

    Got a couple Tubeworks Mosvalve TD723 amps to fix, any schems floating around the nether world?
    Output mosfets are blown, shouldn't be too hard.
    Haven't seen too many of these things out there.
    Thanks, A.

  • #2
    Guess y'all are lucky enough to have never had to mess with one eh?

    I'll try and jot down what I find in case any happen to rear their ugly head in your area!

    Comment


    • #3
      Well after getting the power supply up and running, I was able to make this thing work with an IRFP450 and an IRFP9240 N and P channel FETS in the output section, but they're not the original devices.
      The originals were gone when I got this thing and they should be a T03 package, so now I just have to figure out what kind of output devices this amp is supposed to have.

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      • #4
        If they were T0-3 MOS-FET's then they were most likely 2SJ49 & 2SK134 or 2SJ50 & 2SK135. These are rare and expensive devices now. They used to be relatively cheap and plentiful. If the amp works with the subs, I would probably leave them in there.

        RE

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        • #5
          I actually found a website from the guy who designed these amps (BK Butler) and asked him what devices these came with.
          He was actually kind enough to tell me the originals were 2SK1058 and J162 in a T03 package.
          So time to go searching....

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          • #6
            If you look at the spec sheets the 2SK135 & 2SJ50 are nearly identical to the 2SK1058 and 2SJ162, but in a TO-3 package. I don't see the K1058 or J162 in anything but a TO-3P type flat package. Perhaps they had the output devices custom made, but I would think that they would have just used the commonly available K135 & J50, like most everyone else at the time.

            RE

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            • #7
              I was hesitant to use the flat version 1058 etc. since that's what was in the amp, and they were fried!
              i went with some higher powered IRFP450 and 9240's since we have tons at work, but I'm getting some nasty crossover distortion.
              I'm gonna see if I can rebias them somehow.

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              • #8
                Oh, and I also have a mosvalve power amp which uses the J50 and k135 mosfets, but they appear to be bad also.

                One interesting thing, while studying mosfet amp circuits, this amp has the source pins tied together but they are grounded instead of being the output.
                It derives it's output from the center tap of the +/- mosfet supplies connected to the drains (?).

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                • #9
                  I think the 2sj49 and 2sk134 are available through korg.

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                  • #10
                    Really? I would be most surprised at that. What would they use them in? That part hasn't been made in many years.
                    Education is what you're left with after you have forgotten what you have learned.

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                    • #11
                      No they don't seem to have been made in a while....which is why I suppose I haven't seen these amps around!

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                      • #12
                        July 23, '07 I repaired a Marshall Mosfet Lead 100, which uses the aforementioned FET's. I used a BUZ900 and a BUZ905 as subs. I believe Korg still supplied them at that time.

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                        • #13
                          Ya know, I think replaced those FETS in a Marshall mosfet a while back and have extras.....I think- because I labeled them as Darlingtons, so I'll have to check the part numbers...

                          I'm just bummed that the IRFP450's don't work right since I have a bunch.

                          The amps owner runs a rehearsal studio where my band practices and he has a few Tubeworks mosfet power amps, he gave me one so I could use the mosfets from it, but of course they're bad!

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                          • #14
                            The Mosfet Lead 100 is model # JCM3210. The Korg P/N's are AT134, which is subbed by a Buz900 ($22.87), and AT49, which is subbed by a BUZ905 ($25.50). The prices are list, and are still currently available through Korg

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