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  • Marshall DSL40C strange problem

    Not sure if anyone will be able to help with this, but I am having a problem with my Marshall DSL40C that no amount of google or my very limited electronics knowledge can figure out. Not that its a very expensive amp, but I enjoy problem solving, and have really come to enjoy this amp . So here is the story, amp treated me well for about a year, no problems at all. Was leaving it in an amp stand at my drummers house, where he one day in the process of moving something knocked it off the stand, it landed on the floor and left a gash in the front (didnt hurt speaker though). Was shortly after that, the amp started to completely randomly "stop working" as I was playing it. Out of nowhere, amp went silent in middle of playing, a quick turning the power switch off and on, and boom it was back alive again. This is where things get tricky, as it happens completely randomly, I can in no way duplicate this problem when I want to. The only thing that it seems related too at all is it seems to only happen when the amp is being played louder, at like live gig volume. But even then, I can play through an entire gig and have no trouble, but it will happen the next gig. Another funny thing about it, is that when this happens; it will happen, I will power cycle the amp, then it frequently (not every time) happens again within about 30 seconds, so a pair of failures quickly, then works fine for hours again. I recently put new tubes in this amp, power and preamp, biased both power tubes to 36mv, just throwing that out there in case anyone thought tubes had problem or something. Oh and one more detail, when I power on the amp, there is about a full second pause, then loud clickas the channel light comes on, then amp is operational. I do not remember hearing this loud click before the "accident", but I may be mistaken. Any ideas on this problem would be greatly appreciated, or maybe just let me know what you guys would start with in terms of diagnosis? I can provide more details if needed, thanks for reading!

  • #2
    Check the sticky post called "dreaded switching jack problem" near the top of the maintenance page:
    Maintenance, Troubleshooting & Repair
    It's the most common cause of this type of problem.
    Originally posted by Enzo
    I have a sign in my shop that says, "Never think up reasons not to check something."


    Comment


    • #3
      Well that sucks!
      I can't seem to locate the 'Power On' led on the schematic.

      At any rate, seeing that all of the other led's AND the relays AND the switching ic run off of the +5Vdc regulator, I would resolder that regulator.


      DSL40-60-02-v02.zip

      Comment


      • #4
        This happened to my DSL40C today .Playing & then there was nothing (i thought it was a cable) shut it off & fired it up again & there was sound again .. it did repeat the same problem again . but after unplugging the footswitch for a hour & plugging it back in I could not recreate this problem .I have not inspected the board or taken the chassis out . just wondering if this is a known problem .
        "UP here in the Canada we shoot things we don't understand"

        Comment


        • #5
          Originally posted by copperheadroads View Post
          This happened to my DSL40C today .Playing & then there was nothing (i thought it was a cable) shut it off & fired it up again & there was sound again .. it did repeat the same problem again . but after unplugging the footswitch for a hour & plugging it back in I could not recreate this problem .I have not inspected the board or taken the chassis out . just wondering if this is a known problem .
          See Jazz's post.
          nosaj
          soldering stuff that's broken, breaking stuff that works, Yeah!

          Comment


          • #6
            Originally posted by Jazz P Bass View Post
            Well that sucks!
            I can't seem to locate the 'Power On' led on the schematic.
            It's an illuminated rocker switch.
            Another thing to consider is IC4, the little micro shown below the input jack. It has a reset line and an 'AC detect' line that comes off the LV winding. If the cap or zener at IC4 pin 11 (or any connections to) got glitchy, I think it might mute the amp.
            Originally posted by Enzo
            I have a sign in my shop that says, "Never think up reasons not to check something."


            Comment


            • #7
              I've resoldered all the bad joints & made sure to reflow all the joints on the regulators (All 3 of them) & once in a while the problem still comes back .
              "UP here in the Canada we shoot things we don't understand"

              Comment


              • #8
                One of the issues I've had with a lot of the Marshall amps in our inventory here at CenterStaging, LLC in Burbank, CA, is the Illuminated Rocker Switch itself becomes intermittent. The switch is snap-fit into the rectangular opening, and a bit tricky to extract, but, I've done it repeatedly. Then, to deal with the problem, I carefully pry open the black plastic housing, first releasing one side (where the rocker mechanism has short plastic pins that penetrate into the opening of the housing. Get one side out, then equally careful, do the same on the other side. Tricky move, but once open, I remove the contacts, push out the mating contacts that are a folded contact that are also the 1/4" faston male terminals. With those out, I brush the contact surfaces with a brass bristle brush, then re-assemble it, brush on a little Caig DeOxit, and put it all back together. Switch then works reliably.

                When the switch acts up, as it almost sounds like you're experiencing, it will in use, just turn itself off, stopping the flow of current thru the switch contacts. That usually causes a bit of arcing, which you'd see when you open it up.

                Now, you could just order a new rocker switch and not bother with the procedure I go thru. I happen to like finding out why things happen.

                Just a thought.
                Logic is an organized way of going wrong with confidence

                Comment


                • #9
                  Originally posted by nevetslab View Post
                  One of the issues I've had with a lot of the Marshall amps in our inventory here at CenterStaging, LLC in Burbank, CA, is the Illuminated Rocker Switch itself becomes intermittent. The switch is snap-fit into the rectangular opening, and a bit tricky to extract, but, I've done it repeatedly. Then, to deal with the problem, I carefully pry open the black plastic housing, first releasing one side (where the rocker mechanism has short plastic pins that penetrate into the opening of the housing. Get one side out, then equally careful, do the same on the other side. Tricky move, but once open, I remove the contacts, push out the mating contacts that are a folded contact that are also the 1/4" faston male terminals. With those out, I brush the contact surfaces with a brass bristle brush, then re-assemble it, brush on a little Caig DeOxit, and put it all back together. Switch then works reliably.

                  When the switch acts up, as it almost sounds like you're experiencing, it will in use, just turn itself off, stopping the flow of current thru the switch contacts. That usually causes a bit of arcing, which you'd see when you open it up.

                  Now, you could just order a new rocker switch and not bother with the procedure I go thru. I happen to like finding out why things happen.

                  Just a thought.
                  So your saying even if the power rocker switch is illuminated as well as the other channel indicators it could be the power switch ?
                  "UP here in the Canada we shoot things we don't understand"

                  Comment


                  • #10
                    Originally posted by g1 View Post
                    It's an illuminated rocker switch.
                    Another thing to consider is IC4, the little micro shown below the input jack. It has a reset line and an 'AC detect' line that comes off the LV winding. If the cap or zener at IC4 pin 11 (or any connections to) got glitchy, I think it might mute the amp.
                    Maybe this is something i should be investigating .
                    "UP here in the Canada we shoot things we don't understand"

                    Comment

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