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  • #16
    Originally posted by Valvehead View Post
    V6/7--the meter slowwwwwly creeps up to around 120- 125k ? this is over 10 or 15 minutes until the meter times out and shuts off

    V8/9 instantly measure 150k.
    Does R73 measure 150K ? Does one end measure zero ohms to ground?
    Originally posted by Enzo
    I have a sign in my shop that says, "Never think up reasons not to check something."


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    • #17
      Originally posted by Enzo View Post
      Start looking for conductivity or foreign material on the board in that area. Also look for a tip of a component lead nearby touching that trace. If so, trim it back. Follow the trace from pin 2 to anywhere it goes, looking for anything along the sides of that trace somehow touching it.
      All looks good.

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      • #18
        Originally posted by SoulFetish View Post
        Lift one end of r76 and r78. Is the voltage still there?
        (Assuming you already pull those tubes)
        no---no volts at pin 2

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        • #19
          Originally posted by g1 View Post
          Does R73 measure 150K ? Does one end measure zero ohms to ground?
          yes and yes

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          • #20
            So with C45 removed, you still had 230V at the grids of V6 & 7 ?
            But with R78 & R79 lifted it disappeared?
            Originally posted by Enzo
            I have a sign in my shop that says, "Never think up reasons not to check something."


            Comment


            • #21
              Originally posted by g1 View Post
              So with C45 removed, you still had 230V at the grids of V6 & 7 ?
              But with R78 & R79 lifted it disappeared?
              Yes sir

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              • #22
                Sounds like maybe board leakage, not sure from where.
                You still have the EL84's out?
                Earlier you said 280V at the grids, now it is 230V?
                Point C is 290V? How about pin1 and 6 of PI tube?
                Originally posted by Enzo
                I have a sign in my shop that says, "Never think up reasons not to check something."


                Comment


                • #23
                  After you report back with the voltages g1 was asking about, I want you to try something..
                  Pull the Phase Inverter tube, solder r76 and r78 back in circuit, and power back on. What's the voltage at the grids now?
                  If I have a 50% chance of guessing the right answer, I guess wrong 80% of the time.

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                  • #24
                    Originally posted by g1 View Post
                    Sounds like maybe board leakage, not sure from where.
                    You still have the EL84's out?
                    Earlier you said 280V at the grids, now it is 230V?
                    Point C is 290V? How about pin1 and 6 of PI tube?
                    ok--i was measuring wrong--sorry--


                    el84s out , PI in , all resistors / caps in
                    v6 220v
                    v7 220v
                    v8 0v
                    v9 ov

                    point C 355vdc

                    PI tube pin 1 353v
                    pin 6 354v
                    Last edited by Valvehead; 04-01-2018, 09:52 PM.

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                    • #25
                      Originally posted by SoulFetish View Post
                      After you report back with the voltages g1 was asking about, I want you to try something..
                      Pull the Phase Inverter tube, solder r76 and r78 back in circuit, and power back on. What's the voltage at the grids now?
                      PI pulled , el84s pulled

                      v6 258v
                      v7 258v
                      v8 0v
                      v9 0v

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                      • #26
                        Okay. Just in case you measured something wrong, replace the coupling cap feeding those two grids. Its cheap and thats the logical source of the problem. Report back
                        If I have a 50% chance of guessing the right answer, I guess wrong 80% of the time.

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                        • #27
                          I replaced the .1 caps before

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                          • #28
                            Okay.
                            When you power up are those voltages present on the grids immediately or do they climb to those voltages after some time?
                            If I have a 50% chance of guessing the right answer, I guess wrong 80% of the time.

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                            • #29
                              Originally posted by SoulFetish View Post
                              Okay.
                              When you power up are those voltages present on the grids immediately or do they climb to those voltages after some time?

                              Ok... i just got back from vacation last night. Ready for the madness ? I powered it up to test just now .... and now I have 15 vdc at the grids of V6-7 and 0vdc at v8-9................yep !

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                              • #30
                                Are there any signs that something might have been spilled in the amp? I wonder if there was moisture somewhere that has dried out- maybe under a socket or something? I might hit the board with some compressed air and/or hair dryer. That, and a thorough inspection.
                                "I took a photo of my ohm meter... It didn't help." Enzo 8/20/22

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