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Gibson maestro fuzz tone issues

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  • Gibson maestro fuzz tone issues

    I have one here that I replaced the 3 transistors with the ones small bear sells http://smallbear-electronics.mybigco...zz-a-tort-pnp/.
    All I seem to get is howling feedback. So I bought another set thinking that maybe I ruined them installing without heat sinking them while soldering. With the new set I was careful about heat sinking and still it howls.
    This happens when using the resistors that come with the transistors.
    What is happening here? I've combed over this circuit countless times and nothing seems to be working.
    Can anyone shed some light on this pedal issue?

    thanks
    pete
    Attached Files

  • #2
    Steve/Small Bear is not going to sell you something that has not passed the test, so we can scratch bum trannies.

    That said, it is possible that others have encountered a similar issue. I would recommend contacting SBE with a description of the problem. Be patient, because Steve has to deal with a LOT of correspondence, but you will get a reply. Alternatively, since the majority of pedal builders/folk are usually on the DIYstompbox forum, perhaps your problem would receive a well-informed and more prompt response there.

    Comment


    • #3
      The first thing I would check is the basing... that is always suspect. Substitutes are frequently different. Especially when you are dealing with old tech. What was the original problem? I would put the original transistors back in and trouble shoot from there.

      Comment


      • #4
        You have to double and triple check the transistor pinout. I would have never swapped the resistors until it was working, they aren't that far from stock. Also make sure small bear is using the fz-1a, not the fz-1 for the parts location. He also has his own version of the fuzz with a positive ground. Do you have a transistor checker? If you are going to build any pedals you need one, gives you the pinout too.

        Comment


        • #5
          I should have explained this better. This came to me not working at all and the transistors were not original. They are RS 101 9 (?) made in japan. I changed out the electrolytics and checked all resistors and pots. There was a wrong volume pot value which I replaced. So since there wasn't much else besides the wiring I thought I'd try new transistors. I'm getting sound now but it howls a lot.
          I have a transistor checker an Atlas DCA 55. I will go back and check my pin out on each of these. Thanks for reminding me to use that.
          I was going by the OC77 data on line.

          Comment


          • #6
            That pedal deserves a total rebuild, get rid of those film resistors. Here are a few pictures. You need to find (rca) 2n2613 or 2n2614. You need the leakage or it probably won't bias up right. The earlier model had a 500k pot with a 50k resistor in parallel.
            https://www.coda-effects.com/2016/12...-fz1-1966.html
            https://sites.google.com/a/davidmorr...stro-fuzz-tone

            Comment


            • #7
              I got a kick out of, "If unit should ever need servicing, take it to a reliable radio man. The electrical diagram below should be shown the repairman to assist him in servicing the unit."
              "Yeah, well, you know, that's just, like, your opinion, man."

              Comment


              • #8
                You must have seen this before.

                Click image for larger version

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ID:	853778

                Comment


                • #9
                  Yep. One of my fav's.
                  "Yeah, well, you know, that's just, like, your opinion, man."

                  Comment


                  • #10
                    Originally posted by mozz View Post
                    That pedal deserves a total rebuild, get rid of those film resistors. Here are a few pictures. You need to find (rca) 2n2613 or 2n2614. You need the leakage or it probably won't bias up right. The earlier model had a 500k pot with a 50k resistor in parallel.
                    https://www.coda-effects.com/2016/12...-fz1-1966.html
                    https://sites.google.com/a/davidmorr...stro-fuzz-tone
                    Wow, that brings back memories!! I bought one back in 1966, using it on my Gibson EBO Bass and an Alamo Bass Amp...first of everything on my way to becoming a rock star (dream on!).
                    Logic is an organized way of going wrong with confidence

                    Comment


                    • #11
                      Originally posted by mozz View Post
                      You must have seen this before.

                      [ATTACH=CONFIG]53561[/ATTACH]
                      Yep got one of those hanging on the wall. Coolest Label I've ever seen.

                      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


                      • #12
                        Originally posted by pontiacpete View Post
                        I have one here that I replaced the 3 transistors with the ones small bear sells http://smallbear-electronics.mybigco...zz-a-tort-pnp/.
                        All I seem to get is howling feedback. So I bought another set thinking that maybe I ruined them installing without heat sinking them while soldering. With the new set I was careful about heat sinking and still it howls.
                        This happens when using the resistors that come with the transistors.
                        What is happening here? I've combed over this circuit countless times and nothing seems to be working.
                        Can anyone shed some light on this pedal issue?

                        thanks
                        pete
                        Those solder joints don't look very good to me. Remember heatsink your transistors when soldering.
                        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


                        • #13
                          I quit working on those because I could never find a set of transistors that worked. You blow on those Ge transistors and their bias point changes

                          Comment


                          • #14
                            Originally posted by nosaj View Post
                            Those solder joints don't look very good to me. Remember heatsink your transistors when soldering.
                            nosaj
                            Did the heat sinking as mentioned and no luck. Solder joints are good.

                            Comment


                            • #15
                              Originally posted by cjlectronics View Post
                              I quit working on those because I could never find a set of transistors that worked. You blow on those Ge transistors and their bias point changes

                              Ah ha i'm not the only one. If I can't find the RCA 2n2613 or 14s I'll pass on this repair. I don't see any sense and trying more NOS oc77s or whatever.

                              Comment

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