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marshall jcm 2000 dsl

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  • marshall jcm 2000 dsl

    Hey i bought a used dsl about 3-4 years ago, and to my knowledge that guy bought it new and had it for a couple years. Anyway, its bean giving me a little trouble this past year, and it has been gigged pretty hard i will admit. But my last problem leading to this starts as i replaced my power tubes with el34's, and the next time i turned my amp on i kicked the main power fuse..so i replaced it promptley. Now when i turn the standby on after letting it warm up for a couple minutes i got a little popping and a lot of heat coming from the middle pre amp tube and the third gets very bright, and also some light smoke comes from the middle tube. I also havent done much maintenance(if there is anything i could or should do besides tubes, please let me know) or havenst played it in over 4 months. I slid out the chassis, and discovered no burnt wires or solder joints...do i just need to resolder the main joints? or should i just take it in and get it revamped..anyone else had these problems or know whats up? any help please...thanx dustin

  • #2
    Flip the chassis over. Look next to the socket for the power tube closest to the power transformer. Next to that socket, is there a tiny disc ceramic cap? ANd is it blackened? Or at least shorted? It is wired between pins 3 and 4 of that last socket, so if pins 3 and 4 are shorted together, that cap is why.

    SOmething smoked, so even if you cannot spot it, something burned. COuld be that cap, could be an arcing tube socket, not likely a tube itself smoking.

    If this is beyond you, then it needs to go to your local repair shop. When smoke happens, it is not something that is fixed by plugging in a new tube or somehting.
    Education is what you're left with after you have forgotten what you have learned.

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    • #3
      alright thanks alot enzo..ill look at that.

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      • #4
        My buddy brought over a DSL100 with the C46 cap smoked and three screen resistors open.He also brought one with one of the screen resistors that desoldered itself from the board.The other three measured out fine.Should I check the C46 in this amp as well? How do I measure the cap? Damn these DSL's are nothing but problems.

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        • #5
          Ohm out the cap and check it for a dead short. You want to see a high resistance or the meter ramping up as it charges or moving down as it discharges. If any doubt just change it.Check your traces also from pins 3 to each tube and pin 4 around those resistors. Check the 1ohm current sense resistors going to pin 8 and ground and make sure each bias supply on each side is steady. It it moves up and down I'd change the coupling caps off of the PI too.
          KB

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          • #6
            Anyone in New York that can take a look at this thing for me? I got one done yesterday and it's back tonight again with the same screen resistor popped out again and now 2 of the power tube sockets look like they arced.

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            • #7
              Ouch! You're going to have to replace those arcing sockets. Something is drawing too much current, to cause a resistor to come unsoldered. Is that resistor that fell out connected to one of the arcing sockets? That would be my guess.

              Here's some reading (on similar problems) for ya: http://music-electronics-forum.com/s...ead.php?t=4465

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              • #8
                So sorry to hear about Enzo. Been a staple here and will be forever missed. Always helpful and a top notch tech. Rip Brother.

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