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  • xmt304 help 7

    Happy New Year Everyone!

    I recently purchased a used xmt 304 cc/cv unit (1999) and a 60 series wire feeder with some other equipment for a decent price. I knew the unit had the error code when I bought it. It is a 1999 model 230/460v unit. It is very clean inside and out, figured it was worth repairing as I hear these are good machines.
    When powered up I hear the contactor pull in then a another click then the machine will set for around 15 sec or longer then go into a Help7. the display shows current setting but voltage says .1 or.3 in stick mode. All resistors on side board check good. 20k resistors do get warm. When I took the bolts out of the caps and checked across terminals with an ohmmeter I got just under 20k. When I took the board off It was apparent that some one had been messing with the IGBTs (mitsubishi). But they checked good. I checked them according to a October 24 -25 2008 thread. As far as the diodes... if I use an ohmmeter what should they read? Any help or guidance is greatly appreciated.

  • #2
    i know a guy here in wilm nc. that specializes in welder repair. if u need a number let me know...

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    • #3
      Thanks. I will keep it in mind.

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      • #4
        this is what is listed in the service book.
        Help 7 Display
        Indicates that the input voltage is too high and
        the unit has automatically shut down. Operation
        will continue when the voltage is within
        the acceptable upper range limit (15% above
        the applicable input voltage). Effective with
        KK104771, Help 7 can also indicate a bus
        voltage imbalance (see Section7-9).
        Failed Diode (D1 or D2) on PC2.
        Failed HD1 pulling down +15VDC supply on
        PC1 (unplug hall device to verify).
        Failed IGBT pulling down +15VDC supply on
        PC1 (unplug firing leads RC5 to verify).
        PC2-PLG2 incorrectly inserted into
        PC1-TP1.
        Also to test diodes you need a multimeter that has diode test mode or an old analog meter.
        Be extra careful when powering this units with the cover off. stay to the front and ware a face shield and heavy coat. They can blow up. Remember there is around 325 volts on each of the large caps. These are fatal voltages if you get into them wrong.
        Glenn 300 amp stick
        Millermatic 35
        L-tec plasma

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        • #5
          Thanks for the info. Will check. Yesterday, I was looking at it and decided to try out the machine on lift arc tig and did not get an error although I did not try striking an arc. Diodes d1 and d2 are reading the same. Checked with DVM in diode mode What and where is the HAL? I did notice that the fan does not come on at all when powered up. Is this normal? With most other machines I have seen or used the fan comes on when powered up then shuts off and comes on when needed if the machine has a "fan on demand" setup. How warm or hot should the 20k resistors get? To me they seem to be on the borderline of being hot not warm.

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          • #6
            Xmt

            The 20K bleeder resistors do get quite warm. Assuming you are running the machine on 240 vac, you should get the same voltage on each of the large blue caps, about 340 vdc as I recall. The clicks and delays you describe are normal and you should see a slight jump in cap voltage as you hear the second small click from the top board, pc1, and the caps go up the the final 340 vdc or so. My guess is you have a problem in pc1 or the display board, pc3. The Hall device is the current sensor mounted on the left output terminal and is connected to the pc1 on your machine with a shielded cable and a small white 4 pin connector. We can check any of the devices mentioned here if you like and the boards can be repaired. PM anytime.
            BTW, ccawg is giving you good advice about precautions. The caps are holding a very large amount of energy and if one fails under power, it can provide an experience you will not soon forget. weldersales

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            • #7
              Will check the voltage on caps and the list of things that ccawgc mentioned. Yes I am aware of the safety aspects. I keep as far away as I can when powering it up. Your guidance is greatly appreciated.

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              • #8
                99% of the time Help 7 has to do with the side output board, generally with the bleeder resistors, and/or with the left side igbt. It might test fine, though if you remove the output board, that igbt, may have the base blown off it.

                Will want to verify the protection diodes on the board itself.

                Thi board is rather expensive, though very easy to repair.

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                • #9
                  Originally posted by cruizer View Post
                  99% of the time Help 7 has to do with the side output board, generally with the bleeder resistors, and/or with the left side igbt. It might test fine, though if you remove the output board, that igbt, may have the base blown off it.

                  Will want to verify the protection diodes on the board itself.

                  Thi board is rather expensive, though very easy to repair.
                  All resistors on the side board checked good. When I had the board off, the igbt did not show any visible signs of damage. I did only take of the igbt that is closest to the rear of the machine.
                  Both of the caps have 340v. If I unplug the HAl the open circuit voltage goes up from .3 to 5.3 in stick mode. In lift arc mode, no errors until i try and strike an arc.

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                  • #10
                    When you say someone was messing with the igbts, in what way? Doesn't sound to me that that first one is turning on. They are supposed to be PRX CM100DY-12H.

                    It may be that someone changed the igbt to a non Miller version but didn't fix the driver board for it. Does it look like the protection diode had been changed?

                    Small black unit on the output board with 2 prongs to the left of the igbt mounts.

                    Best to replace the IGBT's with the actual Miller parts. Need the serial# to find out the correct part#'s.

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                    • #11
                      The igbts that are on there are mitsubishi (both). I can tell they have messed with because the white compound on them is smeared. the little boards that are on them may have been resoldered to them just doesnt look like a factory job if that makes sense. How much are new ones? Who is the OEM manufacturer of the igbt?

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                      • #12
                        Originally posted by Semper Fi View Post
                        The igbts that are on there are mitsubishi (both). I can tell they have messed with because the white compound on them is smeared. the little boards that are on them may have been resoldered to them just doesnt look like a factory job if that makes sense. How much are new ones? Who is the OEM manufacturer of the igbt?
                        PRX is the manufacturer though that won't do you any good as you need the driver boards, thats why your best getting them from Miller4less.com, with part#180110, thats the kit with 2 units.
                        Last edited by cruizer; 01-04-2011, 08:47 PM.

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                        • #13
                          Diodes

                          After closer inspection of the board it does appear the diodes have been replaced but the little screws that hold them appear untouched. C1 on the board also seems to have been resoldered or replaced. Again thank you for all of your help!

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                          • #14
                            Yep, the original IGBT's blew, as bolts that hold the board into place likely loosend off, so instead of replacing the IGBT's with the original Miller units, he replaced them with jobbers. Which is fine as long as the driver boards are repaired properly. This is unlikely though. The caps almost never pop unless the internal contactors don't click in for the correct power then they tend to dynamite,

                            You should re examine the output board for damage and replace the IGBT's as a set with the original Miller version.

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                            • #15
                              Well that makes sense. As far as damage to the board, is there anything specific i should look for? Also, Is there anything else I should check out while I have this thing apart. I was thinking of installing the duplex receptacle on the rear of the unit. I looked at the wiring diagram and it appears to just have a pigtail of the appropriate circuit breaker to the hot side and the neutral and the ground are shared and just go to the chassis ground. Am I seeing it correctly?

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