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  • EHX Bass Micro Synthesizer

    Iíve got a vintage big box EHX Bass Micro Synthesizer that isnít working right. The clean signal going through bypassed is garbled at acceptable preamp settings, meaning itís either very quiet or garbled. When the pedal is activated, thereís just some buzz and no effected signal or clean signal passing through. What should be my first course of action in determining the problem? Iím using a Harmon 9v adaptor to power it.

  • #2
    Originally posted by sunshine_bassman View Post
    ......What should be my first course of action in determining the problem?.....
    Upload or link a schematic.
    "Yeah, well, you know, that's just, like, your opinion, man."

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    • #3
      Open it up and meter the power jack, it it still 9v? Assuming it says 9v on the machine. Also check current rating.
      Education is what you're left with after you have forgotten what you have learned.

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      • #4
        Originally posted by sunshine_bassman View Post
        Iíve got a vintage big box EHX Bass Micro Synthesizer that isnít working right. The clean signal going through bypassed is garbled at acceptable preamp settings, meaning itís either very quiet or garbled. When the pedal is activated, thereís just some buzz and no effected signal or clean signal passing through. What should be my first course of action in determining the problem? Iím using a Harmon 9v adaptor to power it.
        I have a 90's microsynth fairly big, it uses either a 24v or 18v wall wart I'll verify after while.
        nosaj
        Binkie McFartnuggets‏:If we really wanted to know the meaning of life we would have fed Stephen Hawking shrooms a long time ago.

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        • #5
          I just went looking at photos. Some are listed on Reverb for sale. One has a nice close up of the power adaptor. It says 24v DC 100ma.

          I looked at several more listings and all said 24vDC 100ma.

          Clearly the 9v adaptor is not the correct one.
          Education is what you're left with after you have forgotten what you have learned.

          Comment


          • #6
            Originally posted by Enzo View Post
            I just went looking at photos. Some are listed on Reverb for sale. One has a nice close up of the power adaptor. It says 24v DC 100ma.

            I looked at several more listings and all said 24vDC 100ma.

            Clearly the 9v adaptor is not the correct one.
            24v 100ma center positive is what I have.
            nosaj
            Binkie McFartnuggets‏:If we really wanted to know the meaning of life we would have fed Stephen Hawking shrooms a long time ago.

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            • #7
              In accordance with the scheme, it is necessary to use a 24 VAC power supply (not 24 VDC).

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              • #8
                I don't see a schematic. The various machines I saw had DC adaptors.
                Education is what you're left with after you have forgotten what you have learned.

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                • #9
                  Here is the schematic.
                  DC power supply can be used, but operation may be unstable when output voltage is 24VDC.
                  30-32VDC is preferable.
                  Attached Files

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                  • #10
                    Originally posted by doctor View Post
                    Here is the schematic.
                    DC power supply can be used, but operation may be unstable when output voltage is 24VDC.
                    30-32VDC is preferable.
                    78 model is ac.
                    90s model is dc
                    Nosaj
                    Binkie McFartnuggets‏:If we really wanted to know the meaning of life we would have fed Stephen Hawking shrooms a long time ago.

                    Comment


                    • #11
                      I've been "repairing" one for the last year and a bit. I had it running properly about February last year, but when I went to reassemble the unit, something either shorted or fractured (damn you with your solid-core wire, EHX!!!). Exasperated, I needed time away from it.

                      That said, the initial repair would not have been in any way possible with this drawing from my good buddy Stephen Giles, in England, who used to work as an accountant for EHX there, and seems to always have arcane pieces of technical info about their products. The schematic can be gotten in many places. Knowing which chip is which is a whole other kettle of fish, though. This drawing sorts that out. It is for the big-box guitar microsynth, but it only differs from the bass unit in terms of a few component values; e.g., for the filter.

                      Click image for larger version

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                      • #12
                        Originally posted by Mark Hammer View Post
                        I've been "repairing" one for the last year and a bit. I had it running properly about February last year, but when I went to reassemble the unit, something either shorted or fractured (damn you with your solid-core wire, EHX!!!). Exasperated, I needed time away from it.

                        That said, the initial repair would not have been in any way possible with this drawing from my good buddy Stephen Giles, in England, who used to work as an accountant for EHX there, and seems to always have arcane pieces of technical info about their products. The schematic can be gotten in many places. Knowing which chip is which is a whole other kettle of fish, though. This drawing sorts that out. It is for the big-box guitar microsynth, but it only differs from the bass unit in terms of a few component values; e.g., for the filter.

                        [ATTACH=CONFIG]57762[/ATTACH]
                        The multiple versions of the microsynth https://encyclotronic.com/synthesize...theszer-r1227/ The first one is the 78 model, second on is the 90s model I have and the others are newer,

                        nosaj
                        Binkie McFartnuggets‏:If we really wanted to know the meaning of life we would have fed Stephen Hawking shrooms a long time ago.

                        Comment

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