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Marshall JCM2000 DSL100 Blown HT Fuse.

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  • #31
    That's some pretty high voltage on the plates and screens. Not saying it's wrong, but I wasn't aware DSLs ran that much B+.

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    • #32
      Originally posted by Greg_L View Post
      That's some pretty high voltage on the plates and screens. Not saying it's wrong, but I wasn't aware DSLs ran that much B+.
      I think those voltages were with all tubes removed.

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      • #33
        Originally posted by Greg_L View Post
        That's some pretty high voltage on the plates and screens. Not saying it's wrong, but I wasn't aware DSLs ran that much B+.
        That's without tubes.

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        • #34
          Originally posted by g1 View Post
          In the video it looks like you have the meter set to measure current? You should be measuring milli-volts DC at those test points.
          $#%&@!!! That could be the problem. DOH !

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          • #35
            Originally posted by The Dude View Post
            Your output tube (socket voltages) look reasonable. Do you have a scope? If so, I'd insert a test tone and follow it through the amp to see where signal is getting lost.
            I'll give that a go. I DID have my meter set on mA instead of mV ,so that's my mistake. I'll check again tomorrow with the right setting then pull the scope out. Thanks !

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            • #36
              Originally posted by gtrplayr1976 View Post

              That's without tubes.
              Doh, yeah I see that now.

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              • #37
                Originally posted by The Dude View Post
                Your output tube (socket voltages) look reasonable. Do you have a scope? If so, I'd insert a test tone and follow it through the amp to see where signal is getting lost.
                It seems to be working now. I got the bias set ,and I have sound. I'm going to run it a few more hours tomorrow to be sure. Hopefully it holds.

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                • #38
                  Originally posted by g1 View Post
                  Possibly. If the cap was shorting before it went open it may have done it. The schematics don't really show where it goes, but your picture shows it definitely connects to the fuse.
                  I have it working. I think that cap was a big part of the issue with the fuse blowing. I'll be testing it more over the weekend just to be sure.

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                  • #39
                    Originally posted by Helmholtz View Post
                    If you have 16.4R between each pin 3 and OT CT, there's no need to measure pin 3 voltages.
                    With tubes out pin 3 voltages will be identical to B+ and with tubes in a couple of volts lower.

                    What is your B+ measured at the OT CT?
                    I have it working now. We'll see if it lasts. I'll test it more over the weekend to be sure the bias holds steady.

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                    • #40
                      Originally posted by Greg_L View Post

                      Doh, yeah I see that now.
                      I have it working for now. I'll be testing more over the weekend. Once I got the meter on the right setting I could get the bias right.

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