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  • #76
    Originally posted by redkurn View Post
    pin 3 to pin 2 = 98.7k *
    pin 1 to pin 3 = 23.3R
    You mean pin1 to pin2 = 23.3R, right? With pin1 being left side looking at the face.
    So the 23R has to be D to S. That means the ON semi datasheet is correct for the ON semi J111. If you still have the old 2N5638 you will find the low resistance (approx.20 to 50R) between pins 2 and 3. So the ON J111 should be installed facing opposite of the 2N5638, which I believe is how you did it.

    "Everything is better with a tube. I have a customer with an all-tube pacemaker. His heartbeat is steady, reassuring and dependable, not like a modern heartbeat. And if it goes wrong he can fix it himself. You can't do that with SMD." - Mick Bailey

    Comment


    • #77
      Originally posted by g1 View Post
      You mean pin1 to pin2 = 23.3R, right? With pin1 being left side looking at the face.
      So the 23R has to be D to S. That means the ON semi datasheet is correct for the ON semi J111. If you still have the old 2N5638 you will find the low resistance (approx.20 to 50R) between pins 2 and 3. So the ON J111 should be installed facing opposite of the 2N5638, which I believe is how you did it.
      I did install it in reverse, but the odd thing is the different datasheets. I did forget to change the 3, but I think I’m being confusing.

      It is installed like this and I numbered by these locations of where I and how I probed, just want to make sure I’m not confusing you or myself.

      This is referring to the image I posted.
      3
      (] 2
      1

      Comment


      • #78
        Originally posted by redkurn View Post

        I did install it in reverse, but the odd thing is the different datasheets.
        Yes, it was stupid for ON semi to reverse their pinout. There are a few other instances of that with different transistors, it's very rare but extremely troublesome.
        So the different datasheet shows how they have reversed their pinout for the ON semi part. You put it in reversed from what was there before so it should work.

        "Everything is better with a tube. I have a customer with an all-tube pacemaker. His heartbeat is steady, reassuring and dependable, not like a modern heartbeat. And if it goes wrong he can fix it himself. You can't do that with SMD." - Mick Bailey

        Comment


        • #79
          Originally posted by g1 View Post
          Yes, it was stupid for ON semi to reverse their pinout. There are a few other instances of that with different transistors, it's very rare but extremely troublesome.
          So the different datasheet shows how they have reversed their pinout for the ON semi part. You put it in reversed from what was there before so it should work.
          I put it in reverse of the original part because the datasheet, maybe I got a little lucky and the whole datasheet thing doesn't matter as much as I originally thought.

          I keep going back to it in my head though, if the resistance is lower on source and drain than source and gate, it would make it DSG or GSD?
          Because the measurements I got have me thinking it is a DSG since pin 1,2 had the lowest resistance 23.3R, am I catching on now?

          Comment


          • #80
            Originally posted by redkurn View Post
            Because the measurements I got have me thinking it is a DSG since pin 1,2 had the lowest resistance 23.3R, am I catching on now?
            Yes. The low resistance reading should be between drain and source. Just a guess, but I think what confuses people about jfets is that they are 'on' in their non-powered state. They require a voltage applied to the gate to turn them off.
            The jfet is most commonly used as a switch. The switch is between the drain and source terminals and the 'command' is applied to the gate terminal. When the jfet is 'on' there is a low resistance between drain and source. This is the switch 'closed'.
            When you apply the correct voltage to the gate, the switch goes 'open', you have high resistance between drain and source, and the jfet is in it's 'off' state.
            The J111 is an 'n-channel' type, so it needs a negative voltage at the gate to turn it off. A 'p-channel' type jfet requires a positive voltage at the gate to turn it off.

            The 2 different datasheets for the J111 part are both correct, but only for their respective brands. ON Semiconductor decided to build their own version of the part recently that had the face pointing the opposite direction from all other J111 jfets that had come before. This was a very irresponsible thing for them to do. So their datasheet is correct, but only for their own version of the part.
            The Fairchild J111 datasheet I posted in post #47 is correct for all other brand J111's, and also matches the pinout for the 2N5638. That is why Yorkville has the J111 listed as a sub for the 2N5638. I think if you ordered a J111 from Yorkville, you would get the older style part (not from ON Semi).

            "Everything is better with a tube. I have a customer with an all-tube pacemaker. His heartbeat is steady, reassuring and dependable, not like a modern heartbeat. And if it goes wrong he can fix it himself. You can't do that with SMD." - Mick Bailey

            Comment


            • #81
              Originally posted by g1 View Post

              Yes. The low resistance reading should be between drain and source. Just a guess, but I think what confuses people about jfets is that they are 'on' in their non-powered state. They require a voltage applied to the gate to turn them off.
              The jfet is most commonly used as a switch. The switch is between the drain and source terminals and the 'command' is applied to the gate terminal. When the jfet is 'on' there is a low resistance between drain and source. This is the switch 'closed'.
              When you apply the correct voltage to the gate, the switch goes 'open', you have high resistance between drain and source, and the jfet is in it's 'off' state.
              The J111 is an 'n-channel' type, so it needs a negative voltage at the gate to turn it off. A 'p-channel' type jfet requires a positive voltage at the gate to turn it off.

              The 2 different datasheets for the J111 part are both correct, but only for their respective brands. ON Semiconductor decided to build their own version of the part recently that had the face pointing the opposite direction from all other J111 jfets that had come before. This was a very irresponsible thing for them to do. So their datasheet is correct, but only for their own version of the part.
              The Fairchild J111 datasheet I posted in post #47 is correct for all other brand J111's, and also matches the pinout for the 2N5638. That is why Yorkville has the J111 listed as a sub for the 2N5638. I think if you ordered a J111 from Yorkville, you would get the older style part (not from ON Semi).
              So based on the readings it must be installed backwards, I installed it based on it being listed as a GSD, but it appears to be a DSG.
              I think when I have it apart, I'll try getting a reading from the resistors again out of circuit and compare to the new ones.
              Also thinking I will flip the fet before I do any of that and see what it does, unless it could damage the output again.

              Just trying to be careful, I know I probably seem like an annoying idiot and I likely am a idiot, but one that is learning. XD

              Comment


              • #82
                Idiots at ON Semi have flipped the pinout again!!! This is brand new, April 2021. They have a new 'Rev.4' datasheet on their website that mouser doesn't even have yet. So maybe mouser are shipping the brand new part. The latest 'rev.4' pinout agrees with the old 2N5638 pinout. That seems to be what you have got.

                So, ON semi rev.2 (March 2006) DSG pinout looking at face (same as 2N5638)
                ON semi rev.3 (Sept.2020) GSD pinout (opposite of 2N5638)
                ON semi rev.4 (April 2021) DSG pinout (same as 2N5638)
                What a nightmare. At least they are back to what it should have always been.

                (edit: I see you had already posted the new one in post #55, sorry I missed it)
                Attached Files
                Last edited by g1; 04-19-2021, 03:18 AM.
                "Everything is better with a tube. I have a customer with an all-tube pacemaker. His heartbeat is steady, reassuring and dependable, not like a modern heartbeat. And if it goes wrong he can fix it himself. You can't do that with SMD." - Mick Bailey

                Comment


                • #83
                  Originally posted by g1 View Post
                  Idiots at ON Semi have flipped the pinout again!!! This is brand new, April 2021. They have a new 'Rev.4' datasheet on their website that mouser doesn't even have yet. So maybe mouser are shipping the brand new part. The latest 'rev.4' pinout agrees with the old 2N5638 pinout. That seems to be what you have got.

                  So, ON semi rev.2 (March 2006) DSG pinout looking at face (same as 2N5638)
                  ON semi rev.3 (Sept.2020) GSD pinout (opposite of 2N5638)
                  ON semi rev.4 (April 2021) DSG pinout (same as 2N5638)
                  What a nightmare. At least they are back to what it should have always been.

                  (edit: I see you had already posted the new one in post #55, sorry I missed it)
                  Yea it's trippy when you see it like that. XD must have had some backlash over it.

                  So I need to flip the fet around when I get it apart and replace the resistors, then probably fixed?
                  I think I will test the original resistors again for giggles.

                  Comment


                  • #84
                    Go figure once the parts arrive things start happening and I am too busy to mess with the amp.
                    One day free so far was today and I didn't really feel like opening it up, but instead spent most of the time trying to learn how to play better.

                    If nothing is going on tomorrow I'll give it a go and see if it is finally fixed and no voltage on the output.

                    Comment


                    • #85
                      -60mv on the output, new resistors in place and J111 reversed, it sounds really nice.
                      The volume knob seems like it will need replaced in the future, but for now it is working.

                      Thanks to all, g1 you sir have helped so very much and taught me a few things.

                      Comment


                      • #86
                        If you haven't, try some Deoxit on the volume control.
                        "Yeah, well, you know, that's just, like, your opinion, man."

                        Comment


                        • #87
                          I did it helped some, but not as much as I’d hoped and they aren’t the easiest kind to get the spray into.

                          They are almost like alpha 9mm pots with the riveted plastic on them, it’s not scratchy really, but cutting connection until it’s at the max. A little wiggling and it works fine enough.

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                          • #88
                            Well definitely do not use a Boss DS-1 on this amp, the fuse just went, powered the pedal on and poof blown fuse, worked fine with my VFE Triumvirate I built though.
                            So I guess it's got an issue still.

                            Comment


                            • #89
                              Can you be more specific, powered on as in connected power to the pedal with no signal going through the chain? Or engaged the effect at high volume? (if the latter, is it back to the stock fuse value?)
                              "Everything is better with a tube. I have a customer with an all-tube pacemaker. His heartbeat is steady, reassuring and dependable, not like a modern heartbeat. And if it goes wrong he can fix it himself. You can't do that with SMD." - Mick Bailey

                              Comment


                              • #90
                                Originally posted by g1 View Post
                                Can you be more specific, powered on as in connected power to the pedal with no signal going through the chain? Or engaged the effect at high volume? (if the latter, is it back to the stock fuse value?)
                                Stock fuse, was playing through it with no pedals and it was fine for maybe 10 minutes, plugged in the VFE pedal and tried it for a couple minutes and then turned that one off and turned the boss pedal on, volume is set low and the gain is maxed, but it shouldn't be or have been the problem.

                                I was plugged into the High channel, I think I may have strummed a string, but all I can recall is the fuse got bright and the amp cut out. I had the volume on the amp about half way up, maybe a little less.
                                I had just got done dialing in a nice clean tone and messed with the scoop knob to see what it was about.

                                22 minutes to break a amp again, got to be a world record there! Probably wasn't something I did though, this amp has seen better days and those resistors were toast, practically fell apart when I removed them.
                                Last edited by redkurn; 04-29-2021, 05:52 AM.

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