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  • 5F6A low volume

    Hi, I re-wiring my own 5F6A clone and now it has a very low volume. What could cause the problem?

  • #2
    Originally posted by vinceg View Post
    Hi, I re-wiring my own 5F6A clone and now it has a very low volume. What could cause the problem?
    Pictures and the schematic you used would be appreciated.

    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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    • #3
      You are right, sorry.
      Attached Files

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      • #4
        I used Ceriatone and Robinette layout for mods
        Attached Files

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        • #5
          Originally posted by vinceg View Post
          You are right, sorry.
          Not sure, but picture 9 might show a diode shorted by a cap's lead.
          - Own Opinions Only -

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          • #6
            Originally posted by Helmholtz View Post
            Not sure, but picture 9 might show a diode shorted by a cap's lead.
            Possible. Thank you for the tip. One thing to watch tomorrow with the light of day. Italy is now evening.

            This could be the cause?

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            • #7
              Originally posted by vinceg View Post
              Possible. Thank you for the tip. One thing to watch tomorrow with the light of day. Italy is now evening.

              This could be the cause?
              Also since you used Dale resistors, we can't tell what the values are. Sometimes a wrong resistor value in certain position can choke the volume. It will be up to you to verify each one against the schematic or layout.

              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


              • #8
                Originally posted by nosaj View Post
                Also since you used Dale resistors, we can't tell what the values are. Sometimes a wrong resistor value in certain position can choke the volume. It will be up to you to verify each one against the schematic or layout.

                nosaj
                I will also control the values of the resistors. Although I doubt they are wrong. Unless Mouser did not make a mistake.

                Anyway, it seems strange to me that the amp does not have a back hiss. I noticed that without guitar plug in there is not classical valve hiss, even raising volume control. Could it be a problem in V1 preamp section?

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                • #9
                  Originally posted by vinceg View Post
                  I will also control the values of the resistors. Although I doubt they are wrong. Unless Mouser did not make a mistake.

                  Anyway, it seems strange to me that the amp does not have a back hiss. I noticed that without guitar plug in there is not classical valve hiss, even raising volume control. Could it be a problem in V1 preamp section?
                  Anywhere in the signal chain can choke the signal, whether it is in the preamp or the poweeramp.

                  See this on page 47 the click test. http://theguitar-blog.com/wp-content...r-Handbook.pdf

                  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


                  • #10
                    Italy is now evening.
                    Same over here in Germany.

                    In winter time most of the day(s) I depend on electric lighting.
                    - Own Opinions Only -

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                    • #11
                      Just curious, did it work properly before the Mods?

                      Personally I have found that by far the best Mod, the one which brings smiles to users, is to rip all of them off and return amp to original circuit, go figure.

                      Not kidding: amps become Classics for a reason: they provide better sound than others since forever, and peak sound and performance was reached after extensive , ear tested modding ... 50 years ago.

                      Once at the peak of the mountain, all paths lead downwards
                      Juan Manuel Fahey

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                      • #12
                        If an amp was working, then you do something to it, and it no longer works right, it is a safe bet the work you did was the cause. SO look especially at every part you changed, every joint you soldered.
                        Education is what you're left with after you have forgotten what you have learned.

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                        • #13
                          Originally posted by J M Fahey View Post
                          Just curious, did it work properly before the Mods?

                          Personally I have found that by far the best Mod, the one which brings smiles to users, is to rip all of them off and return amp to original circuit, go figure.

                          Not kidding: amps become Classics for a reason: they provide better sound than others since forever, and peak sound and performance was reached after extensive , ear tested modding ... 50 years ago.

                          Once at the peak of the mountain, all paths lead downwards
                          Yes, it worked well. I just decided to change the resistors and capacitors and improve the wiring. The mods concern only the bias circuit.
                          However, this night I had a flash of inspiration: I forgot to solder the feedback resistor at the output. I can not wait to run into the lab to see if this is the cause of the problem.

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                          • #14
                            Update
                            I realized I forgot to solder feedback resistor to out. Unfortunately I do not think was the problem. Now the amp has right volume but sometimes it disappears. It also seems to produce some sort of oscillation when I increase the volume control and it has background noise.
                            these are the values I have read:

                            Power transformer has 325+325 V AC than it is correct. At B+ there is 411V DC.

                            V5 (6L6)
                            pin3 400
                            pin4 413
                            pin5 -40
                            pin6 404

                            V4 (6L6)
                            pin3 400
                            pin4 400
                            pin5 -40
                            pin6 407

                            V3 (12ax7)
                            pin1 233
                            pin3 41
                            pin6 236
                            pin8 41.5

                            V2 (12ax7)
                            pin1 170
                            pin3 1.1
                            pin6 310
                            pin8 167

                            V1 (12ay7)
                            pin1 152
                            pin3 2.3
                            pin6 153
                            pin8 2.3

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                            • #15
                              Originally posted by vinceg View Post
                              Yes, it worked well. I just decided to change the resistors and capacitors and improve the wiring. The mods concern only the bias circuit.
                              However, this night I had a flash of inspiration: I forgot to solder the feedback resistor at the output. I can not wait to run into the lab to see if this is the cause of the problem.
                              feedback resistor just lowers the overall gain,assuming it is the right value and the phase is correct,hence negative.Resistor and cap change has a slight effect,for good or worse,only if your building technique is the best possible required,from what i see it's not,sorry,most probably you have some bad soldering or miswire,although voltages are looking fine,which is a good thing.

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