Announcement

Collapse
No announcement yet.

EVH 5150-3 issue

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

  • EVH 5150-3 issue

    Ok.... ive got 2 scems ..1 is a 2006 and other is a 2011 - I think ?? My amp has a 2014 pcb. This amp is a 50w combo with 6L6 and doesnt have the concentric pots.

    So.....When im on BLUE or Green mode.......the Gain pot of Ch3 RED , affects these 2 channels...it should not. Red channel operates normal.

    I suspect Q1 ..it looks like a Mute . J113 transistor . What do you guys think ?

    I can even find Q1 in the amp.......frustrating...
    Attached Files

  • #2
    WELL-----i found that Q1 is REMOVED............wow.

    i am looking thru my bin and found a J111 ---that should work yes ?

    Comment


    • #3
      Installed a J111... green)clean) is ok....Blue CH is still affected by ch3 Red Gain pot...

      Comment


      • #4
        J111, 112 and 113 are very similar and should be interchangeable according to onsemis data sheet.
        Support for Fender, Laney, Marshall, Mesa, VOX and many more. https://jonsnell.co.uk
        If you can't fix it, I probably can.

        Comment


        • #5
          The cutoff voltages are different and given the range of variation within Jfets you could get unexpected operation. A J113 may work as a substitute for a J111, but not necessarily vice-versa, depending on the specific device cutoff voltage.and the circuit voltages. Check the circuit VGS to be sure.

          EDIT: Looking a the schematic and the voltages should be fine for a J111 in that position, though I wonder why Peavey chose to use a J113 when elsewhere in the amp they used J111. You'd think that they'd be wanting to rationalize parts.
          Last edited by Mick Bailey; 11-19-2022, 02:18 PM.

          Comment


          • #6
            Originally posted by Valvehead View Post
            Installed a J111... green)clean) is ok....Blue CH is still affected by ch3 Red Gain pot...
            That really makes no sense.
            Green & Blue are a totally separate circuit from Red.
            If Q1 is working (mutes Red) for Green, then it should also work for Blue.
            Something else must be amiss.

            Comment


            • #7
              II dont know if this helps , but when on the Blue ch. , turning the Gain pot of Red ch. it acts like a wide sweeping treble...not a gain control . I will post a video of me turning the red gain .


              https://youtu.be/SCV2IZcHkFA

              Could it be Z1 / Z2 ? Maybe a relay ?
              Last edited by Valvehead; 11-19-2022, 09:23 PM.

              Comment


              • #8
                So Blue is not ok.
                Good.
                Q1 circuit is still the prime suspect.
                It's not muting the Red channel.
                What is the gate voltage doing when Red is Off & then On?
                I would check every part & connection of that circuit.

                Comment


                • #9
                  Gate is 0.4V blue mode , -07.1v Red

                  i now have a 2011 evh here to compare on the bench

                  The readings are the same on both amps at Gate of Q1 .

                  I took readings on both amps at Z1 / Z2 . heres a pic of that--the bad amp is highlighted =

                  Click image for larger version

Name:	20221120_183012.jpg
Views:	51
Size:	2.87 MB
ID:	973493

                  Comment


                  • #10
                    Verify that 1 is functioning.
                    Pin 2 at V2 A should have no signal when Red is off.
                    If so, then the issue is before that.

                    Comment


                    • #11
                      Originally posted by Jazz P Bass View Post
                      Verify that 1 is functioning.
                      Pin 2 at V2 A should have no signal when Red is off.
                      If so, then the issue is before that.


                      amp on in Blue mode , V2 - pin 2 measures 1mV dc , and .06VAC

                      clipped out Z1/Z2 = no change
                      Last edited by Valvehead; 11-21-2022, 08:58 PM.

                      Comment

                      Working...
                      X