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Marshall Artist, extremely low volume output.

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  • #31
    Originally posted by drewl View Post
    Even though I have rivets and a rivet gun at work I would just use screws and nuts for replacing a socket.
    I usually try to keep it uniform. All screws an nuts or all rivets.
    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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    • #32
      Either way will work fine. If you don't think you will need a rivet gun in the future, go with screws and nuts. Use a drill bit just a little larger than the hole in the middle of the rivet. They drill out quite easily. You might want to put a little grease on first, so the metal filings don't get into anything.
      "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

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      • #33
        Mounting a socket in a old Fender with screws is easy. Now go look at that Peavey the OP is servicing. How you gonna get the nuts on the screws with that board in the way? or would we also rewire the power amp to eliminate the rivets?
        Education is what you're left with after you have forgotten what you have learned.

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        • #34
          Originally posted by Enzo View Post
          Mounting a socket in a old Fender with screws is easy. Now go look at that Peavey the OP is servicing. How you gonna get the nuts on the screws with that board in the way? or would we also rewire the power amp to eliminate the rivets?
          Self Tapping Screws of course.....

          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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          • #35
            Oh and I was confused about what amp we were discussing too.


            And as to self tapping, um, you did say screws with nuts...
            Education is what you're left with after you have forgotten what you have learned.

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            • #36
              Originally posted by mfreqmaster View Post
              Sorry for the delayed response. Hobbyist here with limited time to devote to this. I wiggled the tube socket while on and got a huge change in hum volume/static. So I strongly suspect the 12ax7 socket is bad and not allowing the tube to conduct. I've got a spare. Problem is on the 3203 the socket is riveted in. Any suggestions on how to remove it?
              Have you tried retensioning the socket pins?

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              • #37
                Originally posted by Enzo View Post
                Oh and I was confused about what amp we were discussing too.


                And as to self tapping, um, you did say screws with nuts...
                Good point, you must always be aware whether screwing involves nuts or not.



                EDIT:
                Have you tried retensioning the socket pins?
                Now that you say that, I would also check all solder pads around that socket, a poor/cracked solder joint may lose/make contact when twisting tube, because of PCB flexing.
                Juan Manuel Fahey

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                • #38
                  Originally posted by Enzo View Post
                  Mounting a socket in a old Fender with screws is easy. Now go look at that Peavey the OP is servicing. How you gonna get the nuts on the screws with that board in the way?
                  You and your "real world", always spoiling everything.
                  "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

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                  • #39
                    My world gets more real by the day, and yet it gets less and less real at the same time.


                    Cosmic...
                    Education is what you're left with after you have forgotten what you have learned.

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                    • #40
                      Originally posted by Enzo View Post
                      My world gets more real by the day, and yet it gets less and less real at the same time.


                      Cosmic...
                      You sound like the VW bus in CARS ( cartoon movie lightning McQueen)
                      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


                      • #41
                        Well I know that in an earlier post I said I was a hobbyist with limited time available to work on projects. Apparently my second hobby is extreme procrastination because I finally got those rivets out with a drill and installed a new ceramic 9 pin socket in and rewired everything. The voltages on the 12ax7 pins are similar as before, that is the first triode of the tube doesn't appear to be conducting. I have verified there is 6.3 vac on the heaters and both sides of the tube are lighting up. Even switched 12ax7s and have the same result.

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                        • #42
                          I think the clue is the low pin 2 (input grid ) voltage. Though the absolute values of the measured grid voltages may be not real because of the loading by the meter, pins 2 and 7 should have identical voltages.
                          A low grid voltage means low plate current and thus high plate voltage.
                          So I suspect a leaky coupling cap (C12) as nickb proposed earlier. This would make sense as in this amp the far end of C12 is connected to a low voltage ( 0V) as opposed to the high voltage sometimes.present when coupling tubes.
                          A leaky C12 would pull the pin 2 voltage down.

                          If C12 is good I would look for some leakage path between the grid and ground.
                          Last edited by Helmholtz; 08-10-2020, 07:08 PM.
                          - Own Opinions Only -

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                          • #43
                            I don't know if this is visible, but here is what is located at the C12 location. This looks like a resistor and I measured around 45k ohms across it. This was already there when I bought this and the amp worked well for several months after my purchase. I've ordered a .22 цF capacitor to replace what is on the board. Hard to read the digitized schematic but I think that is the value it calls for.

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                            • #44
                              Actually it is a capacitor but you should replace it as it's suspect.
                              Experience is something you get, just after you really needed it.

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                              • #45
                                The amp had worked fine for a number of months but now it has a super low output.
                                Connect the guitar to the return jack (rear).
                                Do you hear a clear and loud guitar tone?
                                Who does not know and knows that he does not know - teach him Confucius)
                                Who knows and does not know that he knows - wake him Confucius)

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