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EL34 Grid Stopper resistor

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  • Don't touch any bias wire it have no sense to swap bias wires you swap at most the PI outputs but not now
    "If it measures good and sounds bad, it is bad. If it measures bad and sounds good, you are measuring the wrong things."

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    • You must get an 100- 220 pF/ 1-2 kv ceramic cap.
      "If it measures good and sounds bad, it is bad. If it measures bad and sounds good, you are measuring the wrong things."

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      • Originally posted by catalin gramada View Post
        You must get an 100- 220 pF/ 1-2 kv ceramic cap.
        I've got some of those on hand. What to do with it?

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        • Solder it from pin1 and pin6 of v6 directly to the soc,et. Start with 100 pF and power on
          Last edited by catalin gramada; 03-09-2022, 06:53 PM.
          "If it measures good and sounds bad, it is bad. If it measures bad and sounds good, you are measuring the wrong things."

          Comment


          • Originally posted by catalin gramada View Post
            Solder it from pin1 and pin6 of v6 directly to the soc,et. Start with 100 pF and power on
            Any alternatives to a ceramic cap. I've got a 200pF film cap.

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            • Originally posted by ca7922303 View Post

              Any alternatives to a ceramic cap. I've got a 200pF film cap.
              Or a 1000pF 400v film capacitor?

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              • No. Don't use nothing more than 220pF , a ceramic one at 1000v or more slodefed between pin 1 and 6 of v6 directly at the socket
                "If it measures good and sounds bad, it is bad. If it measures bad and sounds good, you are measuring the wrong things."

                Comment


                • Originally posted by catalin gramada View Post
                  No. Don't use nothing more than 220pF , a ceramic one at 1000v or more slodefed between pin 1 and 6 of v6 directly at the socket
                  Will have to order online. Meanwhile, anything I could do to check the xpand/boost switch that has oscillation when engaged?

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                  • Originally posted by ca7922303 View Post

                    Will have to order online. Meanwhile, anything I could do to check the xpand/boost switch that has oscillation when engaged?
                    Correction: found a ceramic that reads 175pF. Will solder in now.

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                    • Originally posted by ca7922303 View Post

                      Correction: found a ceramic that reads 175pF. Will solder in now.
                      Installed ceramic resistor, no change, oscillation with xpand/boost engaged, red plating when ch. 2/3 full gain. Do notice that there is more volume when plugged into 16 ohm jack instead of 4/8 ohm.

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                      • Squeal and red-plating with everything turned to 10 may be normal. No one would ever play the amp that way.
                        Is presence control working yet?
                        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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                        • Originally posted by g1 View Post
                          Squeal and red-plating with everything turned to 10 may be normal. No one would ever play the amp that way.
                          Is presence control working yet?
                          No presence control. It's just not up to full power. Even with everything on 10 then red plating from 8-10. Oscillation now only occurs with xpand/boost engaged. Since the switch actually works, any reason to suspect the switch or the solder job could cause oscillation?

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                          • Originally posted by g1 View Post
                            Squeal and red-plating with everything turned to 10 may be normal. No one would ever play the amp that way.
                            Is presence control working yet?
                            I just noticed that there is no oscillation when both xpand and boost are engaged at same time. If it's only one or the other, oscillation occurs. Red plating occurs to the extreme when all four(4) modern, bright, xpand, boost are engaged and drive/volume/master volume are on full. Sure power tubes will explode if I didn't volume down.

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                            • Originally posted by g1 View Post
                              Squeal and red-plating with everything turned to 10 may be normal. No one would ever play the amp that way.
                              Is presence control working yet?
                              Also seeing now that the red plating is only occuring on one of the power tubes(V8).

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                              • Put those 100k from orange 16 ohm to old blue point back. See if oscillate worse
                                "If it measures good and sounds bad, it is bad. If it measures bad and sounds good, you are measuring the wrong things."

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