Announcement

Collapse
No announcement yet.

JTM 45 build

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

  • JTM 45 build

    I just finished a JTM 45 kit from Mojo and there are issues. The b+ is near 500VDC at all b+ points with just the GZ34 in. Granted, the pre and power tubes draw current, but isn't this a bit high? When I put the pre's and power tubes in I got smoke from the middle of the board. I had them in before and got no smoke but very high b+ readings in the preamp. like 300 +. But this time when I got smoke I immediately shut it down and checked continuity fro the board to the tubes and the board to the pots. All were fine. I just don't know what to do next....Any ideas? Thanks guys....

  • #2
    Some gut shot pictures would help.
    Also Metro has an instruction manual you can download, that has a power up section.
    TubeDepot has one too.
    They show voltages with and without tubes.
    Here are the links to the manuals.
    http://metroamp.com/wiki/index.php/J...t_instructions
    http://metroamp.com/wiki/index.php/5...t_Instructions
    http://site.tubedepot.com/pdf/jtm45plus_v4a.pdf
    http://site.tubedepot.com/pdf/jtm45plus_v4b.pdf
    Last edited by big_teee; 05-30-2013, 04:06 PM. Reason: To Add Info
    "If Hitler invaded Hell, I would make at least a favourable reference of the Devil in the House of Commons." Winston Churchill
    Terry

    Comment


    • #3
      Originally posted by big_teee View Post
      Some gut shot pictures would help.
      Also Metro has an instruction manual you can download, that has a power up section.
      TubeDepot has one too.
      They show voltages with and without tubes.
      Here are the links to the manuals.
      Jtm 45 kit instructions - MetroAmp Wiki
      50 Watt Kit Instructions - MetroAmp Wiki
      http://site.tubedepot.com/pdf/jtm45plus_v4a.pdf
      http://site.tubedepot.com/pdf/jtm45plus_v4b.pdf
      I've got those manuals, but thanks anyway. I have a couple pics but I can't get this bb to upload them. I click on "Insert Image", navigate to the image, and it just hangs.......

      Comment


      • #4
        So are your voltages similar to the Instruction charts?
        Maybe that will show you where your problem or wiring error might be?
        T
        "If Hitler invaded Hell, I would make at least a favourable reference of the Devil in the House of Commons." Winston Churchill
        Terry

        Comment


        • #5
          Terry,

          I can't check the voltages with the tubes in because the board starts smoking...not good! I have a feeling it is a problem underneath the board, because there was continuity to the chassis where there shouldn't be.

          Mike

          Comment


          • #6
            Originally posted by MikeT View Post
            Terry,

            I can't check the voltages with the tubes in because the board starts smoking...not good! I have a feeling it is a problem underneath the board, because there was continuity to the chassis where there shouldn't be.

            Mike
            Roger that Houston!
            May be a good time to build that Dim Bulb tester.
            They are great for what I call Poor Boy Power up!
            dim bulb tester - Google Search
            Good Luck,
            T
            "If Hitler invaded Hell, I would make at least a favourable reference of the Devil in the House of Commons." Winston Churchill
            Terry

            Comment

            Working...
            X