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  • #16
    Originally posted by The Dude View Post
    Are you saying that, when you have the standby switch closed, your 440V B+ drops at the filter caps?
    The 440 B+ doesn't drop, but the second power cap node, 6v6 screens and plates drop down from normal range, while on standby, to abnormally low when switched from standby to play.

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    • #17
      Again, please measure the voltage on both sides of the standby switch (switch closed) and tell us what you have. Then, measure the voltage on the center tap of the primary of the output transformer and report.
      "I took a photo of my ohm meter... It didn't help." Enzo 8/20/22

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      • #18
        Originally posted by The Dude View Post
        Again, please measure the voltage on both sides of the standby switch (switch closed) and tell us what you have. Then, measure the voltage on the center tap of the primary of the output transformer and report.
        Ok the voltage to ground from the rectifier side is now 480. No idea why or how it jumped. Voltage on the other side, connected to the choke lead and OT center tap is 156. The remaining filter cap nodes are 127v for the PI and 111 preamp.

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        • #19
          Hi

          When you check something, please don't tell us it is "fine", please tell us what you measured. We don't know what you consider fine, and we want to know specific values.

          You have 440 at the standby switch? OK. What do you have at the OT CT?

          To me "second node" is the downhill side of the choke, ie the screens. It bothers me you have the SAME voltage at both plates and screens, even though ther is a choke and transformer between those two places.

          What voltages do you get there with power tubes removed?

          The standby switch should be on at all times here. ON means closed, the operate position. You should have your 440v on both sides of that switch.
          Education is what you're left with after you have forgotten what you have learned.

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          • #20
            It may be helpful to note that in a parallel thread on TAG, the OP has revealed a 'trickle bypass' mod to the standby arrangement Deluxe Reverb voltages - Page 2 - The Amp Garage
            Hence standby mode is not as we would normally know it.
            Most amps described as clones aren't; it's way better to provide an accurate schematic, rather than provide text descriptions of deviations to an existing design.

            Originally posted by tyler8611 View Post
            Ok the voltage to ground from the rectifier side is now 480. No idea why or how it jumped...
            Maybe the mains voltage increased a few V? It's a good idea to monitor the mains Vac whilst undertaking such testing, as all voltages from the PT secondary will be a ratio of the primary voltage.
            Last edited by pdf64; 05-30-2018, 10:50 AM.
            My band:- http://www.youtube.com/user/RedwingBand

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            • #21
              Quote Originally Posted by The Dude View Post
              Yes. I understand. If you look at "pin 8 of the rectifier to the first power cap node", follow it up through the OT. It connects directly to the tube plates. If you measure 440VDC there, you should also measure it on the plates, unless you have a horribly bad, hot, melted standby switch. Measure DC on both sides of the standby switch. Is it the same on both with the switch closed?
              Originally posted by tyler8611 View Post
              True and everything is wired correctly. Weird problem.
              PLEASE-ANSWER-WHAT-YOU-ARE-ASKED
              "True" is not an answer.
              "everything is wired correctly" is obviously not the case.

              EDIT:
              PDF64 wrote:
              It may be helpful to note that in a parallel thread on TAG, the OP has revealed a 'trickle bypass' mod to the standby arrangement Deluxe Reverb voltages - Page 2 - The Amp Garage
              Is that so?
              If so, why didn´t you mention it?
              Please post the schematic of said "trickle bypass".

              And remember:
              "Standby ON means switch closed, passing current to the OT and power tubes"

              "Standby OFF means switch open, NOT passing current to the OT and power tubes"

              Nobody knows what trickle Bypass actually means but just from its name it looks like a BAD idea.
              Last edited by J M Fahey; 05-30-2018, 10:48 AM.
              Juan Manuel Fahey

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              • #22
                Originally posted by pdf64 View Post
                It may be helpful to note that in a parallel thread on TAG, the OP has revealed a 'trickle bypass' mod to the standby arrangement Deluxe Reverb voltages - Page 2 - The Amp Garage
                Hence standby mode is not as we would normally know it.
                Most amps described as clones aren't; it's way better to provide an accurate schematic, rather than provide text descriptions of deviations to an existing design.


                Maybe the mains voltage increased a few V? It's a good idea to monitor the mains Vac whilst undertaking such testing, as all voltages from the PT secondary will be a ratio of the primary voltage.
                I've used the standby switch trickle bypass mod on a tweed deluxe build, tweed bassman build and princeton reverb build. Never had a single problem with it.

                I will check and monitor the mains Vac and provide readings.

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                • #23
                  Originally posted by J M Fahey View Post
                  PLEASE-ANSWER-WHAT-YOU-ARE-ASKED
                  "True" is not an answer.
                  "everything is wired correctly" is obviously not the case.

                  EDIT:


                  Is that so?
                  If so, why didn´t you mention it?
                  Please post the schematic of said "trickle bypass".

                  And remember:
                  "Standby ON means switch closed, passing current to the OT and power tubes"

                  "Standby OFF means switch open, NOT passing current to the OT and power tubes"

                  Nobody knows what trickle Bypass actually means but just from its name it looks like a BAD idea.
                  This reminds me of that other forum. Jesus.

                  Comment


                  • #24
                    I'll be providing exact detailed measurements all at once asap. I appreciate you guys.

                    Comment


                    • #25
                      Originally posted by tyler8611 View Post
                      Ok the voltage to ground from the rectifier side is now 480. No idea why or how it jumped. Voltage on the other side, connected to the choke lead and OT center tap is 156. The remaining filter cap nodes are 127v for the PI and 111 preamp.
                      I think several of you guys may have missed this response. This is both sides of standby, switch closed. 480 on one side, 156 other.

                      Comment


                      • #26
                        And I can certainly remove the trickle bypass if anyone thinks it's making this more difficult. But like I said, I've always used it. I think it's a sensible, but obviously not mandatory mod.

                        Comment


                        • #27
                          Originally posted by tyler8611 View Post
                          I've used the standby switch trickle bypass mod...
                          Have you made any other deviations from the DR AB763 schematic and layout? http://schems.com/schematicheaven.ne...b763_schem.pdf
                          Please take a bit of time and review it carefully against your build.
                          We'll assume that a grounded mains cable and chassis have been used, and the death cap and switch omitted, unless you say otherwise.

                          Originally posted by tyler8611 View Post
                          I think several of you guys may have missed this response. This is both sides of standby, switch closed. 480 on one side, 156 other.
                          There may be something wrong with the switch.
                          I suggest that it is removed from the circuit (at least that will remove terminology confusion), and that you then power up via a light bulb limiter.
                          My band:- http://www.youtube.com/user/RedwingBand

                          Comment


                          • #28
                            Originally posted by pdf64 View Post
                            Have you made any other deviations from the DR AB763 schematic and layout? http://schems.com/schematicheaven.ne...b763_schem.pdf
                            Please take a bit of time and review it carefully against your build.
                            We'll assume that a grounded mains cable and chassis have been used, and the death cap and switch omitted, unless you say otherwise.


                            There may be something wrong with the switch.
                            I suggest that it is removed from the circuit (at least that will remove terminology confusion), and that you then power up via a light bulb limiter.
                            Deviations: 1 ohm resistors from pin 8 to ground on the 6v6s, a zener diode string to pull down an overvoltaged PT (also have zeners in my tweed deluxe), 100 ohm resistors on the pilot since my PT lacks a center tap, and copper bus preamp grounding.

                            I don't have a light bulb limiter but I probably do have another new switch that I can substitute. I will check my parts bin.

                            Comment


                            • #29
                              Originally posted by tyler8611 View Post
                              Deviations: a zener diode string to pull down an overvoltaged PT
                              Are those zeners between hi voltage winding center tap and ground? We had a recent thread where that arrangement caused the bias supply to overcharge = excessively high bias voltage. Why? because the current path through the bias supply presented a lower impedance than the current path through the zeners, causing the bias supply to act in an unexpected way. (If there was an entirely separate winding for the bias supply, not just a tap on a hi voltage winding, it wouldn't be a problem.) This isn't a problem with a tweed Deluxe because it is self-biased, iow has no negative voltage supply for fixed bias operation.

                              This may explain one reason for some of your Deluxe's misbehavior.

                              Another, if the meaning of "standby" is inverted, and you have a trickle resistor to partially charge the power supply, it would be expected to see 440V one side of the standby switch and some lower voltage say 153 on the other, when the switch is open. When the switch contacts are closed, the same voltage will exist on both switch terminals.
                              This isn't the future I signed up for.

                              Comment


                              • #30
                                Originally posted by Leo_Gnardo View Post
                                Are those zeners between hi voltage winding center tap and ground? We had a recent thread where that arrangement caused the bias supply to overcharge = excessively high bias voltage. Why? because the current path through the bias supply presented a lower impedance than the current path through the zeners, causing the bias supply to act in an unexpected way. (If there was an entirely separate winding for the bias supply, not just a tap on a hi voltage winding, it wouldn't be a problem.) This isn't a problem with a tweed Deluxe because it is self-biased, iow has no negative voltage supply for fixed bias operation.

                                This may explain one reason for some of your Deluxe's misbehavior.

                                Another, if the meaning of "standby" is inverted, and you have a trickle resistor to partially charge the power supply, it would be expected to see 440V one side of the standby switch and some lower voltage say 153 on the other, when the switch is open. When the switch contacts are closed, the same voltage will exist on both switch terminals.
                                Yes, they're between center tap and ground. There is a separate blue 50v winding for the bias supply.

                                I hear what you're saying on the standby, but somehow the reverse is happening. Doesn't make sense because the standby wires are going to their proper lugs on the switch. I will have to try a new one.

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