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Dynasty 200 DX low output

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  • Dynasty 200 DX low output

    Hey all, just acquired an early Dynasty 200 DX for a very good price, but from what I can tell, the output is about half what it should be. The unit is from a private party, so not a production machine, and it is visually in very good condition with I assume low hours. The only definitive thing I know is that the owner had the machine ground wired to neutral on at his home. He apparently sent it into Miller because he said the stick welding stopped working (he didn't even realize it was welding weak until I told him), and they said to replace the user interface board and control switch board. Serial number is LE313985
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    I performed all pre power checks and everything was right where it should be. I then started looking at the hall device, and did a voltage test on it. I have the 15 and -15 volts at 2 points as I should, but when welding, I'm only seeing half the voltage I should for my amperage setting (confirming my suspicion that the welder is weak). From what I can tell, all functions on the menu are accessible when they should be. It works in ac and dc, but at 200 amps, I have trouble making a puddle on 1/8 steel.

    Any other thoughts on where I should focus my attention? Thanks!
    Last edited by rswright; 07-09-2020, 11:15 AM.

  • #2
    When doing the pre-power checks, did you check the IGBTs on the underside of the machine and the resistance checks for the gate drivers for those IGBTs that are on the board screwed to them? Does it have low power only on AC, or on DC as well?

    Also, visually inspect for overheated connections, especially at the busbars for the igbts on the underside, the secondary rectifiers, the connections to the dinse/tweco connectors on the front panel, and anything else that carries weld current.

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    • #3
      I did look at the snubber board (pc6) in the manual and all pre power tests were okay.

      I only confirmed the DC weld was weak with the hall device, but I do feel like the ac was weak as well when I tested the machine before receiving it.

      I will go ahead and take a look at the igbt area again and confirm everything appears okay visually.

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      • #4
        When welding, does the display show approximately the current you set before welding, or a lower number? (may need a helper, setting your phone to record a video, or a load bank, unless you can weld while looking at the screen not the weld...)

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        • #5
          Originally posted by Bushytails View Post
          When welding, does the display show approximately the current you set before welding, or a lower number? (may need a helper, setting your phone to record a video, or a load bank, unless you can weld while looking at the screen not the weld...)
          Just checked. The amps I'm seeing are just under half what I should be seeing. Setting the unit to 125, with a full pedal, the unit is displaying 52 amps. At 200 amps, it only made it to 83 amps. Conincides almost exactly with the values I witnessed testing the hall device directly.

          This is a different pedal than the one I originally used when i noticed the condition, so I'm fairly certain I can rule that out, unless the issue is on the machine end of the remote connection.

          Still have yet to look at the igbt area again, I'll let the capacitors drain and take a look in a bit.

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          • #6
            Have you already checked the ribbon cable from the front board to the inverter control board? What is the output voltage on the DC bus? How are you checking amps? I haven't tried it on a Dynasty 200, but usually crow bar the outputs to run my amperage tests. Start with it in stick mode, minimum amperage and slowly increase amperage. Since it's shorted across the output, it draws low power. If you're still getting low amperage, it's either the front board or the connection between the front board and inverter board. If you're getting full amps, it sounds like it would be a power issue, possibly one of the IGBTs not firing.

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            • #7
              Originally posted by jjohn76 View Post
              Have you already checked the ribbon cable from the front board to the inverter control board? What is the output voltage on the DC bus? How are you checking amps? I haven't tried it on a Dynasty 200, but usually crow bar the outputs to run my amperage tests. Start with it in stick mode, minimum amperage and slowly increase amperage. Since it's shorted across the output, it draws low power. If you're still getting low amperage, it's either the front board or the connection between the front board and inverter board. If you're getting full amps, it sounds like it would be a power issue, possibly one of the IGBTs not firing.
              Looked at the ribbon cable and tested everything there. Only items I got nothing on were the fan, but I don't think that's the issue.

              Output voltage on DC bus was 26 volts or so iirc when testing with the Tig at 200 amps.

              I'm testing amps by either looking at the display or checking the reading on the hall device. Both match values based upon the technical doc.

              I went into stick mode, set amps to 20, shorted it, and saw 35 amps on the machine display. Did the same thing at higher values (up to 100 amps) and still saw 35 amps holding the crowbar in place. Each time I saw roughly .8v.

              Does the front board (pc3 or weld control board as it's referred to in the manual) control the amperage or is that the inverter control board? It seems as though the front board is receiving the correct information (that current is lower than nominal), but it's not correcting. Each time, the current is also proportionally low to the nominal value. The ratio is roughly 2/5 of desired output.

              The igbt area looks flawless. Attached a pic for viewing. The entire machine is flawless inside, no electrical smells or anything.

              The only area on any of the boards that looks questionable is R1 on the power interconnect board (pc2). I don't think it's a bad joint, but I could be wrong... Looks like a bit of a sloppy soldering job.

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              • #8
                A failing transzorb on the control board might be able to cause that. Since you're just testing, put it in stick mode, set the output to "on", and do not connect a pedal. I'm not sure if that actually bypasses all the zeners on the plug, but it's worth trying.

                But, before poking at the control circuitry, check for bad connections on the secondary power stuff first, especially the back of the front-panel dinse connectors.

                If everything looks clean and tight, then check the voltages to/from the pedal. I'm pretty sure it's 1V/100A. The unit should put out 1V to the pedal for each 100A selected, and the input from the pedal, at full pedal, should be the same. At least, that's how it works on a different, older unit I've worked on, and I'm guessing is how a dynasty might work, but they won't give a schematic...


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                • #9
                  Bushy, the reference amperage to/from the pedal is from 0-10 V, with 10V as max amperage in this case 200a. On the remote socket, pin D is your reference, pin C is the panel amperage to the pedal, 0-10V DC based on 0-200a set at the panel. Pin E is your remote amperage 0- voltage on C. That's in line with what you should see on Pin 11 of the ribbon cable (pin 16, 17 or 18 are your reference for this voltage) Oddly enough, the Dynasty does have actual output voltage and amperage readings available on the remote, and they followed the 1V/100a and 1V/10V you mentioned above. I would guess they read out in pin F (output amperage) and H (output voltage) like the XMTs. Maybe someone had in mind to make this work with an optima 200 mig pulser...

                  If the remote C reads appropriate with changing the panel amperage and you're pedal potentiometer is working right, it's worth checking at Pin 11 on the ribbon cable if you can get to it.
                  Last edited by jjohn76; 07-09-2020, 09:59 PM.

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                  • #10
                    I just went out and checked my 200dx, and at least when not welding, C-D is always 10V regardless of the current set on the front panel. So, instead of looking for the front panel setting on the pedal connector, you'd want to check for 10V C-D and, with the pedal down, 10V E-D as well.

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                    • #11
                      Thanks Bushy. That's odd, the tech manual says it should vary 0-10V. It isn't the first typo on a pin voltage in that manual...

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                      • #12
                        Originally posted by Bushytails View Post
                        I just went out and checked my 200dx, and at least when not welding, C-D is always 10V regardless of the current set on the front panel. So, instead of looking for the front panel setting on the pedal connector, you'd want to check for 10V C-D and, with the pedal down, 10V E-D as well.
                        So... Just had a chance to check on the voltage on pedal connections. Looks like I have a constant 10v C-D. When I floor the pedal, I get only 4v E-D, but, C-D also drops to 4v, so the pedal and it's connections are fine.

                        That 4v volts occurs on hf or lift arc Tig, stick, AC or DC at any amp setting. Pin 11 values vary wildly (2v for Tig hf, 0v for lift arc, 10 or 12 v for stick AC/DC respectively). Again, amp setting plays no role.
                        Last edited by rswright; 07-12-2020, 02:18 PM.

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                        • #13
                          Sounds like a lot like a bad transzorb on the E pin. That's an easy, cheap fix!

                          If the voltage on the E pin only goes up to 4V, and full scale is 10V, the welder will think you're only pushing the pedal 40%. 80A is 40% of 200A, like you measured earlier.

                          I believe they're a P6KE12A. Will run you about 50 cents.

                          It could be some other part of the input circuitry, but I'd give an almost certain chance of it being the transzorb.



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                          • #14
                            Originally posted by Bushytails View Post
                            Sounds like a lot like a bad transzorb on the E pin. That's an easy, cheap fix!

                            If the voltage on the E pin only goes up to 4V, and full scale is 10V, the welder will think you're only pushing the pedal 40%. 80A is 40% of 200A, like you measured earlier.

                            I believe they're a P6KE12A. Will run you about 50 cents.

                            It could be some other part of the input circuitry, but I'd give an almost certain chance of it being the transzorb.


                            That seems very logical. Going to see if I can source one at my electronics store tomorrow and give it a go. I've identified the diode as the one directly below the plug. I compared the voltage drop to the bank of those same diodes and they were the same. But, this diode had much less resistance than all the others, so I'm hopeful that's a sign it is indeed cooked. I know you'd typically provide 10-12v and measure the loss, but it's in such an easy area to solder I'll risk it.

                            If this works, I got this welder for the cost of the diode and a case of beer.

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                            • #15
                              I'll give you two cases of beer for it!

                              Transient suppressor diodes aren't something most electronics stores will have a good selection of, unless you have a very well-stocked store. You might have to go to mouser or one of the other online suppliers.

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