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  • My amp died.............

    Hey guys.

    I was at band practise earlier and while I was playing, my Marshall JTM60 combo just cut out. The mains power was still there, it just lost all sound.

    I looked around the back and 1 of what I believe to be the power valves was glowing immensely (more than the other power valves) and was extremely hot. So I turned the amp off, unplugged it and left it alone.

    I've noticed over the last week or so that my 60w valve combo has had trouble keeping up with the other guys Peavey Bandit or 40w Marshall valvestate combos, so I figured it was maybe ready for a new set of valves.

    Does this sound like a symptom of being a valve problem? If not, what could it be and what should I do about the amp?

    Thanx for any info.

    Craig

  • #2
    Re: My amp died.............

    There are fuses a bit hidden in that amp. At least 2. You have to yank the chassis out to get to them. I would try that first.

    Danger Will Robinson, high voltages at play here. Enought to send you off to that "long sleep", if you know what I mean.
    Jackson, Ibanez & Ovation Guitars
    Laney, Marshall & Peavey Amplification

    ((tube max dissipation wattage / amp plate voltage) x % of max dissipation wattage) x 1000 = bias current in mA

    "There was never a horse that couldn't be rode, never a man that couldn't be throwed." - Marshall Matt Dillon - GUNSMOKE (1959)

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    • #3
      Re: My amp died.............

      Originally posted by wixedmords
      There are fuses a bit hidden in that amp. At least 2. You have to yank the chassis out to get to them. I would try that first.

      Danger Will Robinson, high voltages at play here. Enought to send you off to that "long sleep", if you know what I mean.
      Hi there.

      Thanx for your reply

      To be honest I don't really want to be taking this amp apart myself because I know i'd either make the problem worse, or kill myself in the process I'm not the best guy when it comes to work such as this.

      Craig

      Comment


      • #4
        Re: My amp died.............

        Craig,

        You know a healthy JTM60 is WAY louder than a Bandit or a 40w Valvestate.

        I reckon an output valve died and you've been running on just one for a while. There are only 2 power valves in a JTM60 - the big ones (EL34s). Are they both glowing? (Take the black metal grille thing off if you can't see properly). An EL34 died in my JTM60 once and the symptom was a sudden drop in volume.

        Power valves and fuses are the obvious things to check/change, but if that doesn't work it might be best to see a tech.

        Simon

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        • #5
          Re: My amp died.............

          It's not a fuse. If the fuse had blown, the amp wouldn't power up at all. That's the point of having a fuse.

          I'm guessing that it's a tube (valve) problem. $20 should get you up and running again. It could be something more sinister, but I doubt it. It needed new tubes (valves) anyway, so start there.
          Mr. Way Too Proud of Texas Guy

          Nothing nothing nothing, nothing nothing nothing nothing nothing.

          Comment


          • #6
            Re: My amp died.............

            Originally posted by HamerPlyr
            It's not a fuse. If the fuse had blown, the amp wouldn't power up at all. That's the point of having a fuse.

            I'm guessing that it's a tube (valve) problem. $20 should get you up and running again. It could be something more sinister, but I doubt it. It needed new tubes (valves) anyway, so start there.
            Ah, HP, not true. There are fuses on board in this one. I have one, and it did this same thing.

            Not talking about the main fuses.

            But, a tube is easier to get at.
            Jackson, Ibanez & Ovation Guitars
            Laney, Marshall & Peavey Amplification

            ((tube max dissipation wattage / amp plate voltage) x % of max dissipation wattage) x 1000 = bias current in mA

            "There was never a horse that couldn't be rode, never a man that couldn't be throwed." - Marshall Matt Dillon - GUNSMOKE (1959)

            Comment


            • #7
              Re: My amp died.............

              Originally posted by HamerPlyr
              I'm guessing that it's a tube (valve) problem. $20 should get you up and running again. It could be something more sinister, but I doubt it. It needed new tubes (valves) anyway, so start there.
              This tube/valve thing is hilarious. Let's call the whole thing off.

              Comment


              • #8
                Re: My amp died.............

                Originally posted by Simon_F
                This tube/valve thing is hilarious. Let's call the whole thing off.
                Exactly. Everyone knows "tube" sounds better than "valve"
                Those who live by the sword get shot by those who don't.

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                • #9
                  Re: My amp died.............

                  Originally posted by Simon_F
                  This tube/valve thing is hilarious. Let's call the whole thing off.
                  You say potato...

                  I say tomato

                  Guitars: Frankinstein TeleBird/Classic Vibe Esquire w/BG-1400/Martin 000-28EC
                  Amps: 3rd Power Dream Solo 4 '68 Plexi/Port City Wave 2x12
                  FX: Skinpimp Faceplant/Skinpimp 3OD/Flyin' Dragon


                  https://itunes.apple.com/us/album/fa...wn/id786464154
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                  • #10
                    Re: My amp died.............

                    Two different fuses, huh? Why?
                    Mr. Way Too Proud of Texas Guy

                    Nothing nothing nothing, nothing nothing nothing nothing nothing.

                    Comment


                    • #11
                      Re: My amp died.............

                      Originally posted by HamerPlyr
                      Two different fuses, huh? Why?
                      One's a heater fuse. I am not sure about the other. They are in a fairly hard spot to get at, but not impossible. It is a complicated amp to work on.

                      Respect given HP. Just trying to help the original poster.
                      Jackson, Ibanez & Ovation Guitars
                      Laney, Marshall & Peavey Amplification

                      ((tube max dissipation wattage / amp plate voltage) x % of max dissipation wattage) x 1000 = bias current in mA

                      "There was never a horse that couldn't be rode, never a man that couldn't be throwed." - Marshall Matt Dillon - GUNSMOKE (1959)

                      Comment


                      • #12
                        Re: My amp died.............

                        No, no... I appreciate the correction. I'm just surprised, I've never owned an amp that had two fuses.
                        Mr. Way Too Proud of Texas Guy

                        Nothing nothing nothing, nothing nothing nothing nothing nothing.

                        Comment


                        • #13
                          Re: My amp died.............

                          It's a stinker, 2 on the board, 1 in the mains.
                          Jackson, Ibanez & Ovation Guitars
                          Laney, Marshall & Peavey Amplification

                          ((tube max dissipation wattage / amp plate voltage) x % of max dissipation wattage) x 1000 = bias current in mA

                          "There was never a horse that couldn't be rode, never a man that couldn't be throwed." - Marshall Matt Dillon - GUNSMOKE (1959)

                          Comment


                          • #14
                            Re: My amp died.............

                            Actually, a lot of ampegs come with 3 fuses, mains, and 2 heaters... as well as some other amplifiers, it is done to protect the tubes. You will probably be looking at another problem if the heater fuse blew as in most cases(over 50% of which) there is an underlying internal cause to a blown fuse. Take it to a competant tech(which are hard to find) and let them take care of it. Youll save time and your life possibly.
                            IMO, you should, if not properly trained and educated, take it to a tech. I have see too many hack jobs in my shop which have cause much greater problems then the original cause. You will probably save money in the end.
                            Gypsy, give me your tears. If you will not give them to me, I will take them from you.

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                            • #15
                              Re: My amp died.............

                              As wrong as I was on the fuse thing, I still say to replace the power tubes. Even if it doesn't fix the problem, you end up with a pair of spares that you should have anyway.
                              Mr. Way Too Proud of Texas Guy

                              Nothing nothing nothing, nothing nothing nothing nothing nothing.

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