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Twin Reverb - Amp circa 2005 Trem issues

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  • #16
    The 4 pin 'tapped' balance pot is an oddball that you can't get any more and confuses things.
    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
      The negative bias is applied to the grid of the oscillator tube via the 2.2M resistor and biases to tube into cutoff to stop the LFO.
      When the junction between the 1M and the 2.2M is grounded the grid voltage jumps from around -50V to zero and starts the LFO.
      The bias voltage has no effect on the LFO operation.
      - Own Opinions Only -

      Comment


      • #18
        Originally posted by Helmholtz View Post
        The negative bias is applied to the grid of the oscillator tube via the 2.2M resistor and biases to tube into cutoff to stop the LFO.
        When the junction between the 1M and the 2.2M is grounded the grid voltage jumps from around -50V to zero and starts the LFO.
        The bias voltage has no effect on the LFO operation.
        2.2m sets up a proportional bias so if the -50V is more positive in the circuit, the proportion is going to be to close to the output stage current curve. Giving it more negative bias will increase that proportion ratio.

        Comment


        • #19
          Originally posted by g1 View Post
          The 4 pin 'tapped' balance pot is an oddball that you can't get any more and confuses things.
          Never had a problem getting those. Maybe you are looking in the wrong places.

          Comment


          • #20
            Originally posted by sparkies View Post
            2.2m sets up a proportional bias so if the -50V is more positive in the circuit, the proportion is going to be to close to the output stage current curve. Giving it more negative bias will increase that proportion ratio.
            As said, the bias voltage has absolutely no effect on LFO operation.
            Read the schematic.
            The footswitch shorts any (negative) grid voltage to ground, otherwise the LFO will not work.
            Last edited by Helmholtz; 02-09-2024, 07:04 PM.
            - Own Opinions Only -

            Comment


            • #21
              Originally posted by sparkies View Post

              Never had a problem getting those. Maybe you are looking in the wrong places.
              How about posting a source for those 4 pin tapped pots. You've already demonstrated that you don't even know which pin is the wiper.
              Originally posted by Enzo
              I have a sign in my shop that says, "Never think up reasons not to check something."


              Comment


              • #22
                Originally posted by g1 View Post

                How about posting a source for those 4 pin tapped pots. You've already demonstrated that you don't even know which pin is the wiper.
                Your avatar suits you . because the 15K is on the wiper.

                I find it interesting that you can't find this:
                Click image for larger version

Name:	P271-DS21R10K.jpg
Views:	81
Size:	47.3 KB
ID:	993747
                On of my generic electronic suppliers I buy from has 42 of them in stock.
                But of course seeing your country of origin explains a lot, especially the attitude.

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                • #23
                  Originally posted by sparkies View Post
                  Your avatar suits you
                  .
                  Originally posted by sparkies View Post
                  But of course seeing your country of origin explains a lot, especially the attitude.
                  The right thing to say would have been "I think you missed the pot layout in the schematic symbol". Instead you chose personal insults and even demonstrated some intolerance regarding people of a specific nation. So hear this cupcake...

                  I'm going to start a private meeting with a few others here. And when it's over I'm pretty sure we won't be hearing from you again.
                  "Take two placebos, works twice as well." Enzo

                  "Now get off my lawn with your silicooties and boom-chucka speakers and computers masquerading as amplifiers" Justin Thomas

                  "If you're not interested in opinions and the experience of others, why even start a thread?
                  You can't just expect consent." Helmholtz

                  Comment


                  • #24
                    Originally posted by Chuck H View Post
                    .


                    The right thing to say would have been "I think you missed the pot layout in the schematic symbol". Instead you chose personal insults and even demonstrated some intolerance regarding people of a specific nation. So hear this cupcake...

                    I'm going to start a private meeting with a few others here. And when it's over I'm pretty sure we won't be hearing from you again.
                    I am not going to feed into your perceived intolerance and if you look at the thread, you will see he was picking on me instead of contributing to the thread.

                    Comment


                    • #25
                      Originally posted by sparkies View Post

                      Your avatar suits you . because the 15K is on the wiper.

                      I find it interesting that you can't find this:
                      Click image for larger version

Name:	P271-DS21R10K.jpg
Views:	81
Size:	47.3 KB
ID:	993747
                      On of my generic electronic suppliers I buy from has 42 of them in stock.
                      But of course seeing your country of origin explains a lot, especially the attitude.
                      Yet still no source to help others?
                      nosaj
                      soldering stuff that's broken, breaking stuff that works, Yeah!

                      Comment


                      • #26
                        No he wasn't picking on you. The worst he said was that you didn't know where the wiper was in the schematic. This is much less personal than your reaction. Had you even replied with "No it's YOU that doesn't know where the wiper is." I could have stood for that as it would be equal to the remark. If you don't see the difference it's going to be a problem for you here.

                        My percieved intolerance is accurate as far as that goes. We live in different times and there are current and prominent ideologies that are supported by the majority of this forums constituency. And we don't tolerate intolerance. You probably thought you were being clever or funny but you only managed to be inappropriate.

                        So far the private meeting has revealed one member that thinks you deserve a warning. Well here it is. Hope you heard it. And while you're at it hearing things you might go ahead and edit your post as a demonstration of better intentions. I could do it myself but that's not the point.
                        "Take two placebos, works twice as well." Enzo

                        "Now get off my lawn with your silicooties and boom-chucka speakers and computers masquerading as amplifiers" Justin Thomas

                        "If you're not interested in opinions and the experience of others, why even start a thread?
                        You can't just expect consent." Helmholtz

                        Comment


                        • #27
                          Originally posted by nosaj View Post

                          Yet still no source to help others?
                          nosaj
                          Well since you asked, here is one:
                          https://www.digikey.com/short/mmv715m8

                          Comment


                          • #28
                            Originally posted by Chuck H View Post
                            No he wasn't picking on you. The worst he said was that you didn't know where the wiper was in the schematic. This is much less personal than your reaction. Had you even replied with "No it's YOU that doesn't know where the wiper is." I could have stood for that as it would be equal to the remark. If you don't see the difference it's going to be a problem for you here.

                            My percieved intolerance is accurate as far as that goes. We live in different times and there are current and prominent ideologies that are supported by the majority of this forums constituency. And we don't tolerate intolerance. You probably thought you were being clever or funny but you only managed to be inappropriate.

                            So far the private meeting has revealed one member that thinks you deserve a warning. Well here it is. Hope you heard it. And while you're at it hearing things you might go ahead and edit your post as a demonstration of better intentions. I could do it myself but that's not the point.
                            Do you do anything else than be a busy body and defend the two somewhat clueless hecklers? - Not really.

                            Comment


                            • #29
                              Originally posted by sparkies View Post

                              Do you do anything else than be a busy body and defend the two somewhat clueless hecklers? - Not really.
                              Clueless? Who's clueless? You mean the guys that demonstrated your error about bias supply voltage on the trem circuit? Nah. Can't be those guys. They were contributing useful information. And in fact they did it by directly countering your information. According to your post above you seem to think the opposite is true. Nevermind that the part you linked has nothing to do with the trem circuit but that matter is taking up room in a thread about a different circuit entirely. Is THAT useful content?

                              Surprisingly, I'll stand for the personal attack on me just now.
                              "Take two placebos, works twice as well." Enzo

                              "Now get off my lawn with your silicooties and boom-chucka speakers and computers masquerading as amplifiers" Justin Thomas

                              "If you're not interested in opinions and the experience of others, why even start a thread?
                              You can't just expect consent." Helmholtz

                              Comment


                              • #30
                                Originally posted by sparkies View Post

                                because the 15K is on the wiper.

                                I find it interesting that you can't find this:
                                Click image for larger version

Name:	P271-DS21R10K.jpg
Views:	81
Size:	47.3 KB
ID:	993747
                                On of my generic electronic suppliers I buy from has 42 of them in stock.
                                Yes, my mistake, when you were speaking about the 3K3 resistor I thought you were saying it connected to the wiper rather than the tap.
                                And I mistook you for a previous member which was reflected in my attitude so I apologize for that.

                                Now you still have not explained how anything related to the bias circuit could affect the opto. And the pot you referenced is not a recessed slotted adjuster like Fender used, so you would have the pot shaft sticking out the back of the amp. That is why they are considered 'No Longer Available'.

                                Originally posted by Enzo
                                I have a sign in my shop that says, "Never think up reasons not to check something."


                                Comment

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