XMT 304 cc/cv help.

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I have an XMT 304 cc/cv 230v/460v. I am in the military and when i left it was a running unit.  i have returned to find that when i switch it on i have no display and it hums.  if i switch between processes the hum changes tones.  any thoughts as to what this could be? My wife told me while I was away my father came over and used my welders for a project he was working on but he swears when he shut it down it was working as it should.  One more thing, I removed the case and noticed the 4 large black caps on the circuit card are bulging slightly.  i have 4 units i got for parts in various stages of disarray.  should i remove the caps from one of there boards and put them on mine? all the values are the same between them but the plug ins are different so I cant just swap out boards. thanks in advance
Reply:You don't have any help# codes? I am by any means an expert but I think you have issues that aren't the caps.
Reply:i have zero display.  when i switch it on it sits for a moment and then it starts humming. no display at all
Reply:I would check the power and connections!  Bulging caps, not good, probably should be replaced!GlenMiller Dynasty 200DX - Millermatic 350P - Hypertherm Powermax 45Want to sell!! - Hobart Handler 150
Reply:just swapped out front display card. everything works perfect again.  now as far as swapping caps, is it feasible to remove the ones from the donor board and solder them on.  and i also have the xfmer and hookups to ad the 115v plug to my xmt.  if i added those parts to mine would that be an issue?  as far as i can tell from my manual i only need to add the parts and change the xfmer.  thanks again for all your sugestions.
Reply:I would replace the bulging caps with new ones if it were me.Miller Syncrowave 350Millermatic 252/ 30A spoolgunMiller Bobcat 225g w/ 3545 spoolgunLincoln PowerArc4000Lincoln 175 Mig  Lincoln 135 Mig Everlast 250EX TigCentury ac/dc 230 amp stickVictor O/AHypertherm 1000 plasma
Reply:would the bad caps cause the machine to be sluggish when switching between processes? i have ordered the de-soldering tools to remove the old caps and will replace when it gets here.  Is there any other thing that could be causing this? I Googled the issue with no results. thanks again
Reply:Also was wondering if the humming is a normal occurrence.  I don't recall it humming previously.  Or maybe I have just been away from welding and my shop that im hearing a problem that doesn't exist.Miller Syncrowave 180sdMiller Syncrowave 250 Tig RunnerMiller XMT 350Miller Suitcase Xtreme 12VSMiller DialArc 250Miller Trailblazer 302Lincoln Invertec V300 ProTorchmate CNC Plasma Table
Reply:Good to hear you got it running. This hum  is it low pitched or more of a crackle ? Mine has a fairly quiet hum  to it but not excessive. Maybe something is loose and vibrating inside.
Reply:Sounds like a transformer hum.  Probably all it is. As far as switching between processes, why would it be sluggish? Also if I switch to lift arc I have all zeros displayed and my volts dance between 16.9 and 18.4.  All other processes work alto slow to respond when dial turned. Any thoughts?Miller Syncrowave 180sdMiller Syncrowave 250 Tig RunnerMiller XMT 350Miller Suitcase Xtreme 12VSMiller DialArc 250Miller Trailblazer 302Lincoln Invertec V300 ProTorchmate CNC Plasma Table
Reply:It takes a few seconds for the display when you switch process. As for tig volts I never really looked at mine, I just go by the amps.
Reply:on my xmt at work when set on lift arc tig i have an amp reading and volt.  also by sluggish i mean when i switch process from stick set to 100 amps to scratch start, the amps read zero for a few seconds, and sometimes i have to turn amp knob to get the amperage to show.  I too generally go by the amps,  but as it is on lift arc i have no amperage reading to go by.  makes no sense to me.Miller Syncrowave 180sdMiller Syncrowave 250 Tig RunnerMiller XMT 350Miller Suitcase Xtreme 12VSMiller DialArc 250Miller Trailblazer 302Lincoln Invertec V300 ProTorchmate CNC Plasma Table
Reply:Are you set to panel, not remote.
Reply:set to panel.  the hum is the same for scratch tig, stick, v sense feeder.  no hum on ntig, mig, pulsed mig or cc.  hum on lift arc is a higher pitch.Miller Syncrowave 180sdMiller Syncrowave 250 Tig RunnerMiller XMT 350Miller Suitcase Xtreme 12VSMiller DialArc 250Miller Trailblazer 302Lincoln Invertec V300 ProTorchmate CNC Plasma Table
Reply:You should have the same amp rating with your process switch set to tig, lift tig ,stick and CC. The mig and vs settings would be different. I would set it on stick ,set your amps, then switch to lift tig and see if it works.
Reply:I have done that. Lift arc is the only process that displays  no amps as it should. All other processes read as they should.  I have tried to leave it sitting on lift arc to see if the display changes with no luck.  If I switch from stick or scratch to lift arc it displays amps for a fraction of a second then goes blank. Have replaced the Display board with no change.  Also checked all wires and plugs and all checks out. I rarely use lift arc anyway but id like to know what is going with the machineLast edited by richardson3709; 12-17-2014 at 10:25 PM.
Reply:installed the 4 new caps on board and now all processes are working.  on to trying to repair the other 304.  when hooked to power and switch flipped instantly blows breaker and main. nothing in the unit looks burned or desoldered. igbt's look OK.  need to test them but unsure of the procedure on that.  what other possible areas may be causing a dead short?Miller Syncrowave 180sdMiller Syncrowave 250 Tig RunnerMiller XMT 350Miller Suitcase Xtreme 12VSMiller DialArc 250Miller Trailblazer 302Lincoln Invertec V300 ProTorchmate CNC Plasma Table
Reply:

Originally Posted by richardson3709

installed the 4 new caps on board and now all processes are working.  on to trying to repair the other 304.  when hooked to power and switch flipped instantly blows breaker and main. nothing in the unit looks burned or desoldered. igbt's look OK.  need to test them but unsure of the procedure on that.  what other possible areas may be causing a dead short?
Reply:6 year old thread.caps = capacitors. should be the low voltage power supply caps on the main control pcb on top. Be careful working on them. there is stored high voltage on the large buss caps and if something fails while the cover is off it can blow pieces of plastic across the room or into your eyes. Before you you attempt to power them up. Use an ohmmeter to check the input diodes and IGBTs for any shorts at the terminals.either in ohms or diode test. If you have a cap test mode measure the buss caps.make sure they are close to rated value and even. Check the two diodes next to the IGBTs and all the power resisters. Look in the vents on the back for anything that looks burnt or discolored. If all appears ok. set cover on and power up.Are these single or two voltage auto link welders? start out with lowest line voltage they will run on first, Less likely to make a big bang.Miller has forbidden all service techs from giving out the tech manual.to down load a manual we have to agree, that we will be the only user of the down load. Plus the service tech is supposed to have completed level one of their training. just for us to use it.Last edited by ccawgc; 11-14-2020 at 01:02 AM.
Reply:hi.thanks for the reply.ive just put up a post about my xmt 304 and a few problems im having with it.really appreciate any input you can give me..love to hear back from you..