Announcement

Collapse
No announcement yet.

K-MOD101 Kit DYI Amp -40% Voltage at V1 plate (12AX7 pin 6)

Collapse
X
 
  • Filter
  • Time
  • Show
Clear All
new posts

  • #31
    Originally posted by TelRay View Post

    - completely removed the VOLUME POT from the circuit and measured 20 Ohm to 1,016 Ohm from the wiper to both HOT and COLD lugs (it is a 1M pot). So I think the range the pot is controlling is OK
    This confuses me. Is that 1,016 kohms? I would expect it to get a bit closer to zero ohms the other way as well. The fact that it doesn't respond to bass and treble does make it sound like crosstalk like Enzo said.

    Comment


    • #32
      Is the 22µ cathode cap good and well connected? If not, some signal will be coupled via the V1A and V1B cathodes bypassing tone and volume controls.
      In this case signal would spill over even if pin 7 is directly grounded.

      Another possibility would be a bad (high ESR) node E filter cap.
      Last edited by Helmholtz; 06-07-2020, 12:57 AM.
      - Own Opinions Only -

      Comment


      • #33
        Originally posted by glebert View Post
        This confuses me. Is that 1,016 kohms? I would expect it to get a bit closer to zero ohms the other way as well. The fact that it doesn't respond to bass and treble does make it sound like crosstalk like Enzo said.
        my bad, 1,016 KOhm as you pointed out
        thx

        Comment


        • #34
          Originally posted by TelRay View Post
          my bad, 1,016 KOhm as you pointed out
          thx
          Well, that's very high. If this is at the grounded end of the pot, it will let some signal pass. Around 60dB down from full volume.
          - Own Opinions Only -

          Comment


          • #35
            Originally posted by Helmholtz View Post
            Well, that's very high. If this is at the grounded end of the pot, it will let some signal pass. Around 60dB down from full volume.
            isn’t that the expected value for a 1MOhm pot?
            maybe the original typo (now corrected in the post) brought some confusion

            the pot’s range goes from 20 Ohm to 1.02 MOhm

            Comment


            • #36
              Originally posted by TelRay View Post
              isn’t that the expected value for a 1MOhm pot?
              maybe the original typo (now corrected in the post) brought some confusion

              the pot’s range goes from 20 Ohm to 1.02 MOhm
              Oh, my bad. Seems I misinterpreted. Funny "translation" error. Reason is that over here 1.000 means 1k and 1,000 means 1. We don't use a decimal point but rather a decimal comma.
              So I thought you had 20R minimum resistance at one end (between wiper and outer termination) and 1k minimum resistance at the other end.
              Last edited by Helmholtz; 06-07-2020, 04:20 PM.
              - Own Opinions Only -

              Comment


              • #37
                Originally posted by Helmholtz View Post
                Oh, my bad. Seems I misinterpreted. Funny "translation" error. Reason is that over here 1.000 means 1k and 1,000 means 1. We don't use a decimal point but rather a decimal comma.
                So I thought you had 20R minimum resistance at one end (between wiper and outer termination) and 1k minimum resistance at the other end.
                i feel you brother!
                coming from metric system world too i had a period of “americanizing” myself to the decimal point and thousand separator comma myself

                i’ll check those capacitors soon and report back to headquarters

                Comment


                • #38
                  Originally posted by Helmholtz View Post
                  Is the 22µ cathode cap good and well connected? If not, some signal will be coupled via the V1A and V1B cathodes bypassing tone and volume controls.
                  In this case signal would spill over even if pin 7 is directly grounded.

                  Another possibility would be a bad (high ESR) node E filter cap.
                  both caps measured (they were OK with the MMT, I do not have an ESR checker) and replaced.
                  The problem is still there (sound with volume at zero not affected by treble or bass)

                  You guys were mentioning "cross-talk"earlier is this what I have just tried to solve by testing those capacitors or is it something else?

                  thx!

                  Comment

                  Working...
                  X