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XMT 350 Arcreach No ouput, No Codes

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  • XMT 350 Arcreach No ouput, No Codes

    I'm looking for some troubleshooting advice on this machine, it was working fine with my Arcreach suitcase, then all of the sudden, nothing. Powers up fine, no codes and appears to function, but won't power the suitcase when the gun trigger is pulled and won't produce more than a small spark in stick mode.

    I opened it up and found the +15v power to the hall sensor was only +5 volts and VR1 on the PC1 board was extremely hot. Something is pulling the positive rail down. Is the front control panel the culprit since I don't have any codes? Serial #MF306189U. Thanks for the help.

  • #2
    Hopefully Bushytails is still monitoring. He has spent much more time on the XMT 350s than me. All of the below asses the Arc Reach is an XMT350 with different software in the front board (if that). I am working through an XMT 350 main board right now and can offer hopefully something helpful for you:

    Be careful leaving it on too long. That 15V circuit is powered through the auxiliary inverter (the big power module under that finned heatsink at the back of the main board. That auxiliary inverter has a built in current limit, but it can still fail (happened on 3 of the 5 main boards I have on hand). If the voltage regulator gets too hot and fails, it may take out your auxiliary inverter (or it might even be what failed). If you have a current controlled power supply, it's best to use that to power the 15V circuit.

    That 15V circuit powers the front half of your main board, the hall sensor, the front board, and possibly the gas solenoid if your XMT 350 has that option installed. So there are a lot of things that could have shorted/failed to cause that issue. I usually use a IR camera to find the hot/failed parts because it's the fastest and easiest. If you don't have one and are good with electronics, you could troubleshoot it, bit I would caution that there are some high (lethal) voltages present on the boards.

    I would turn the machine off, let the big capacitors discharge, disconnect all of the connectors across the main board, do the pre-power checks for the inverter circuit on the main board, and do a resistance/diode check across VR1's output and circuit common. I would do a similar resistance/diode check across the front board's +15V and COM, as well as the +15V and COM for the Hall Sensor. I would also check across the VR1 input and COM to see whether or not it failed. This may narrow it down to one of the main boards/components. If it doesn't, there is likely a short on a component down stream of a transistor. Either way, it's probably component replacement at that point and worth taking in to a tech.

    Hope this helps. Let me know if you need any more info or make any more progress.

    Comment


    • #3
      Thank you for taking the time to reply! I downloaded the closest tech manual I could find online (Red-D-Arc Extreme 360, is there a closer match available?) there are some differences on the MOD 1 & 2 tests, but I checked what I could. I went through the Control/Auxiliary Power PC1 Inverter Control Circuit Test, all values were in tolerance except for Diode 11. It shows continuity both directions. I don't know if that piece of info points in a certain direction or not. I checked the +15 rail voltage with the hall sensor both plugged and unplugged with no change.

      I have a mechanical engineering degree, so I'm not super well versed in circuits, but have more experience then some. I might make more headway if they provided circuit schematics, but I know that's not the case. I bought the machine used, in February, and haven't had a single problem till the output dropped dead. Is there somewhere to send these PC1 boards for repair? I hate to send the machine to Miller for service, since even though I live in the biggest city in MT, the service center is 4 hours away in Gillette, WY. I only have 1800$ in the machine, and it looks like a new PC1 is around 1000$.

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      • #4
        No worries about the ME, my background is mechanics too. It all blends once you have to fix something someone else engineered...
        You may be able to buy the right tech manual for it off eBay, or a local Miller tech may send one to you if you ask. I usually start with the ones readily available and can figure out the rest. Of the XMT 350 main boards I have seen, the only major changes I found were the early ones had a pull-down resistor on the auxiliary inverter current feedback circuit, the mid-ish ones changed that to a pull-up resistor (I am assuming to deal with the issue that the current sense shunt in the module fails open), and the later ones use a different fan power circuit (probably some common failure with the Q1 triac).

        What were the two differences in the pre-power checks?

        I am working on the schematic for the main board, just haven't had the time to finish it. By Diode 11 showing continuity in both directions, do you mean 0V drop in both directions? Either way, it should read just the same as D20. If it doesn't, that's looks to be a good starting point. That diode is part of the main inverter gate driver circuit through the T4 gate drive transformer.

        Jon

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        • #5
          Jon,
          D11 reads .009, D20 reads .2, the specified range is .2-.9. Definitively not the same reading. From the look of it, the circuit that D11 is in is a mirror image of the circuit that D20 is in. I'm pretty sure the failure is related to that area of the board.
          The differences I saw between the manual and the machine board were in checking MOD2. Some of the specified diode test points weren't on the board, I think it was D8, D10, D11.

          Thanks for the help.
          Jon

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          • #6
            Jon,

            I'll look into those checks. The Dynasty 200 went through some similar changes where it added a test point between the snubber capacitors to check the snubber IGBTs. I haven't drawn the interconnect schematic yet, but the half bridge and snubber layout from the XMT350 looked the same as for the Dynasty/Maxstar 200, albeit larger/more modules.

            Diode D11 looks to be part of the clamp/snubber for Q7, which is part of the gate drive circuit for Inverter Snubber 1 (through Gate Drive Transformer T4). Yes, both D11 and D20 are mirror components in the gate drives for Snubber 1 and Snubber 2. D11 connects the drain of Q7 to the +15V rail (in parallel with R38). The source of Q7 is tied directly to the COM. The drain of Q7 is also tied to one side of the T4 primary. And the gate of Q7 is tied to pin 5 of U13, which is also connected to the other side of the T4 primary (sorry for the terrible netlist...). T3 is driven the same way with D20, R52, Q10, and pin 7 of U13.

            So... When U3 pin 5 signals low, the gate of Q7 is low, Q7 drain is floating high (+15V minus voltage drop in R38), and T4 primary is reverse biased (my convention) with the current through it limited by R38. Once U3 pin 5 signals high, the gate of Q7 (also connected to one side of T4 primary) goes high, the Q7 drain is pulled low, which forward biases transformer T4. Diode D11 I am assuming is there as the free wheeling diode to protect Q7 when the current in T4 switches directions. Since it's shorting, it's worth replacing D11 and checking/replacing Q7 and U13 as well if necessary. Q7 is most likely damaged too since it was basically a dead short of +15V across it any time U13 pin 5 signalled high. U13 may be ok since it was current limited by the current resistor across the T4 secondary (part of your PM2 checks for the interconnect board).

            Sorry for the lack of clarity, hopefully this helps,

            Jon

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            • #7
              Quick note - you can measure diode drop across the source and drain of Q7. The more I think about it, if U13 pin 5 to common measured ok (pre-power check), then there's a good chance Q7 is ok, but still worth checking.

              Comment


              • #8
                Jon,
                I should have mentioned that I pulled D11 and checked it out of the circuit, it tested fine once removed. I replaced it with a new diode since I was already there, with no change obviously. I will look up the components for Q7 & U13 and order some replacements to see where that gets me.
                Thanks,
                Jon

                Comment


                • #9
                  That's odd, the only parallel connections I am seeing to D11 are R38, the loop through the T4 primary to pin U13-5 to +15V, or through Q7 (D->G) to pin 13-5 to +15V. Did U13 check out in the Inverter Pre-Power checks?

                  Comment


                  • #10
                    Jon, diodes D8-D11 in the pre-power checks are the Snubber gate protection diodes. It's worth finding/checking them to see if there are any problems with your Power Mod 2. If you post pictures of your main board near U13,Q7,Q10,T4 and the interconnect board near the top of PM2, I could probably point you in the right direction.

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                    • #11
                      I just rechecked the U13 tests. Either something changed since I previously ran through the PC1 inverter control tests, or I missed it, U13 Pin 5 to RC9 pin 4 shows near zero voltage drop (.009), U13 Pin 7 to RC9 pin 4 is within range (.2). Seems to me like u13 failed. I will order replacements for U13 and Q7 to see if anything changes.

                      Comment


                      • #12
                        Jon,
                        Attached (hopefully) are the two images you asked for. I made it through the MOD1 tests on the PC2, but there are some differences between my machine and the manual on MOD2.

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                        • #13
                          Sounds good. It's definitely worth checking PC2 for the Snubber protection diodes. They are most likely 15V zener diodes connected anode to anode between the Snub_1 G and Snub_1 E signal lines coming from PC1 to PC2. It's probably just as easy to do a diode check on every diode on PC2 (should be less than 20, pick whatever polarity is easier and just make.sure none read .009V on your multimeter - some will argue against this method and they're right, but it's worked for me so far...). It's especially important to rule out any issues with the PM2 Snubber 1 since the Snubber 1 driver has issues.

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                          • #14
                            Jon, it looks like Miller updated the gate driver voltage clamps on PC2 for the Snubber and Inverter IGBTs, as well as added protection diodes on the inverter/snubber gate drivers on PC1.

                            On the older PC2 boards (look at the pre-power checks) you will see pairs of diodes - they're zener diodes connected anode to anode and between the gate and emitter, which basically clamped the gate voltage to between ~ +/- 16.5V of the emitter. On the newer board, Miller replaced it with a Transient Voltage Suppressor (TVS) diode, which does the same thing.

                            If you see right next to all of the gate drive transformers (T1, T2, T3, T4) there are a pair of Shottky diodes. I suspect these clamp the drive signals from U13, U16, and U17 the same way. One of those next to T4 likely connect between U13 pin 5 and +15V, and could be another faulty component. The pairs should be connected anode to cathode, with the lower anode going to COM, the upper cathode going to +15V, and the anode-cathode junction going to either Pin 5 or Pin 7 of the driver ICs (U13, U16, U17). That's my guess, but can't confirm.

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                            • #15
                              Either way, I am sure those diodes are in the updated pre-power checks (D50, D52, D54-59). I am curious where D51 and D53 are on PC1. The higher number diodes should be in the back right corner of the board.

                              Also, it looks like Miller added L3 to PC2. Possibly an update to the snubber circuit?

                              Hope this helps,
                              Jon

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