Announcement

Collapse
No announcement yet.

Please advice me how to do 5150 combo bias mod

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

  • Please advice me how to do 5150 combo bias mod

    Hi

    I want to mod my 5150 combo. I find out the schematic is different with 5150 amp head.

    Please see the schematic, is this 47k a bias resistor?
    If yes, I should choose 22k or 47k trimmer? And what value resistor ? 10k?

    And I want to add 1ohm resistor to the power tube pin, to check the ma. I did it for vintage Marshall. How can I do it?

    Thank you

    Is img_8451.jpgClick image for larger version

Name:	IMG_8451.JPG
Views:	2
Size:	49.6 KB
ID:	871852

  • #2
    And keep in mind that the 5150 was deliberately designed with a lowish bias in mind.

    If you goose up the current it messes with the 'Resonance' control.

    Comment


    • #3
      Originally posted by Jazz P Bass View Post
      And keep in mind that the 5150 was deliberately designed with a lowish bias in mind.

      If you goose up the current it messes with the 'Resonance' control.
      Agreed. IMO, there is nothing to be gained by this mod.
      "I took a photo of my ohm meter... It didn't help." Enzo 8/20/22

      Comment


      • #4
        I'm sure you are right. I've deleted my suggested mod.

        Comment


        • #5
          Originally posted by The Dude View Post
          Agreed. IMO, there is nothing to be gained by this mod.
          How about reduced tube life?
          (I'm sure the tube dealers would disagree with you)
          Originally posted by Enzo
          I have a sign in my shop that says, "Never think up reasons not to check something."


          Comment


          • #6
            Yeah, if you are not wearing out a set of tubes every few months, you must not be rocking.
            Education is what you're left with after you have forgotten what you have learned.

            Comment

            Working...
            X