Announcement

Collapse
No announcement yet.

Marshall JCM2000 DSL100 High Current Draw

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

  • #16
    Sorry about that. I must have missed the original photo.

    W4 and W5 are internally connected on the board, but since they aren't in use, I'll ignore them.

    Comment


    • #17
      I see now that the trace connects W4 and W5. Wires from the PT were never connected at these two points.

      Comment


      • #18
        I'm looking at your first photo and the PT primary side wiring along with the additional wiring with their tie wraps and lengths. Doesn't seem like it would be possible to mix up reds, blue or brown.

        As for the PT, I think one winding has red to blue, with the second winding having red to brown. I'm trying to see if I can find any photos of when I worked on this amp in the past, but am coming short at the moment.

        With the xfmr wires lifted from the board, what are the resistance readings you get from red to red, red to blue, red to brown, blue to brown? That might help determine if your transformer is shorted on the primary side, or at least determine the two sets of windings. Wouldn't be the first time this amp has had a failed PT or perhaps even an internal miswire.

        Comment


        • #19
          Originally posted by Delta362 View Post

          With the xfmr wires lifted from the board, what are the resistance readings you get from red to red, red to blue, red to brown, blue to brown? That might help determine if your transformer is shorted on the primary side, or at least determine the two sets of windings. Wouldn't be the first time this amp has had a failed PT or perhaps even an internal miswire.
          red to red, open

          red to blue, 2.34 ohms

          red to brown, 1.97 ohms

          blue to brown, open

          Comment


          • #20
            If you connect only the red/blue set to the power supply board and leave the red/brown disconnected, as well as leave the secondary disconnected, does your DBT (or LBL, dim bulb tester or light bulb limiter, your choice of nomenclature) glow brightly? If not, then next try with the red/brown set connected to the board without any secondaries.

            Comment


            • #21
              I found the Interconnect List I had made a while back. It's actually for the TSL-100, but much of the details apply to the JCM 2000.

              TSL-100 Amp Head Interconnect Cables List .pdf
              Logic is an organized way of going wrong with confidence

              Comment


              • #22
                Originally posted by Delta362 View Post
                If you connect only the red/blue set to the power supply board and leave the red/brown disconnected, as well as leave the secondary disconnected, does your DBT (or LBL, dim bulb tester or light bulb limiter, your choice of nomenclature) glow brightly? If not, then next try with the red/brown set connected to the board without any secondaries.
                Not using a bulb. I am watching the current on the variac meter. I tried each pair separate. Same issue.

                Dialing the V to just 3 to 5 VAC brings the current up fast to .5 A. Another 5 VAC brings it up to 1 A. I dial it down quickly. I have a 3 A slow blow fuse in the mains holder.

                Comment


                • #23
                  I don't believe you have tried it with all the primary wires disconnected yet? This will test for any issues with the power switch wiring etc.
                  Originally posted by Enzo
                  I have a sign in my shop that says, "Never think up reasons not to check something."


                  Comment


                  • #24
                    Originally posted by g1 View Post
                    I don't believe you have tried it with all the primary wires disconnected yet? This will test for any issues with the power switch wiring etc.
                    I was wondering about that. With all primary cables disconnected, I can connect my AC directly to the two center red wire taps on the primary?

                    Thank you

                    Comment


                    • #25
                      Originally posted by misterc57 View Post

                      I was wondering about that. With all primary cables disconnected, I can connect my AC directly to the two center red wire taps on the primary?

                      Thank you
                      No, to go direct you would connect to one of the sets Delta362 mentioned in post #20.

                      But what I really meant was just plug AC (variac) into the amp and monitor current like you have been doing, but with all PT primary wires disconnected. This takes the PT completely out of the equation and tests the wiring for any other faults that could be causing the current draw.
                      Originally posted by Enzo
                      I have a sign in my shop that says, "Never think up reasons not to check something."


                      Comment


                      • #26
                        What I was having you test was one of the two primary windings at a time. You'd have hot on red and neutral on brown to test the first set. Then the next set would have hot on the other red and neutral on blue. You won't/don't connect hot to one red and neutral to the other red as you'll get neither transformer winding energized properly.

                        Comment


                        • #27
                          Sorry folks. I am getting confused on the primary wiring and testing. I have edited the schematic section to include the wire colors. See pic.

                          In looking at this section of the schematic. I see the mains hot connecting to one winding "brown-red" and the mains neutral connecting to the other winding "blue-red".

                          So I would think to connect directly to the PT primary I would connect the mains hot to brown, the mains neutral to blue. I believe when you tell me that is wrong but I do not understand why.

                          If I want to bypass all the switches, etc, and connect directly from mains to the PT primary, I can only do one winding at a time? hot to brown, neutral to red being one test, then hot to blue, neutral to red being the next test?

                          Thank you



                          Click image for larger version

Name:	pt-schem.JPG
Views:	194
Size:	165.6 KB
ID:	922704

                          Comment


                          • #28
                            You measured 2.34 ohms from one of the red leads to the blue. I have highlighted that PT primary winding in green in the attached. You then measured 1.97 ohms for the other winding (the other red wire to the brown), which I've highlighted in purple. What I'd like for you to test is to connect only the windings I've highlighted in green then power on. Does that draw lots of current? If so, then that winding has an internal short somewhere and your PT is bad.

                            If that does not draw lots of current, then remove that winding and connect only the winding I've highlighted in purple, and power that on. Does that draw lots of current? If so, then that winding has an internal short somewhere and your PT is bad.

                            If one or both of those draw lots of current, then you have a shorted internal winding. If neither draws lots of current, then connect it so both the green and purple highlighted windings are connected. Then power that arrangement on. Does it draw lots of current? If so, then you have a breakdown of insulation between the two sets of windings and your PT is shot, and will need to be replaced.
                            Attached Files

                            Comment


                            • #29
                              Originally posted by Delta362 View Post
                              You measured 2.34 ohms from one of the red leads to the blue. I have highlighted that PT primary winding in green in the attached. You then measured 1.97 ohms for the other winding (the other red wire to the brown), which I've highlighted in purple. What I'd like for you to test is to connect only the windings I've highlighted in green then power on. Does that draw lots of current? If so, then that winding has an internal short somewhere and your PT is bad.

                              If that does not draw lots of current, then remove that winding and connect only the winding I've highlighted in purple, and power that on. Does that draw lots of current? If so, then that winding has an internal short somewhere and your PT is bad.

                              If one or both of those draw lots of current, then you have a shorted internal winding. If neither draws lots of current, then connect it so both the green and purple highlighted windings are connected. Then power that arrangement on. Does it draw lots of current? If so, then you have a breakdown of insulation between the two sets of windings and your PT is shot, and will need to be replaced.
                              Not seeing any attachment.

                              Thank you

                              Comment


                              • #30
                                Uploading this time as pdf instead of jpg.
                                Attached Files

                                Comment

                                Working...
                                X