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  #1  
Old 09-24-2007, 10:17 PM
tom.jelly tom.jelly is offline
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Default dead xmt304...did I find the (only) problem??

Got a good deal (I think, if I can fix it!) on a dead XMT304 (does nothing when you turn on the switch) opened it up and I can see a bit of smoke got let out of the board right by the area in the photo where the three black power leads are. the big question is, if this spot is burnt, what caused it and did it wreck anything else. the second picture shows where the enlarged detail is from, plus a spot on the toriodal transformer that doesn't look too good, but the spot on that insulation looks like it might have been melted by some spark ember from the thing that gave up in the enlargement, as the wire underneath looks good. Any suggestions on troubleshooting this would be appreciated before I give up and bring it in for service.

Tom
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Old 09-25-2007, 04:46 AM
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GWIZ GWIZ is offline
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I don't think I can help.
I never worked on one, all I can do is make alot of ASSUMPTIONS.

I cant read the markings on the board you covered them with your arrows.
Appears a plastic yellow capacitor maybe C6 the "C" usually means capacitor.
What I can make out of it, that type of cap will not short-out and fry on its own.
One of two things would do it excessive voltage but unlikely.
The second, more likely the heat from the power resistor ( long brown thing R7) took its toll and melted the Cap's coating then the cap fried.
The burnt spot under the resistor maybe normal over time.

You also have a bad crimp connection cable T1. that's ready to catch fire if you get this working.


The toroidal transformer,
That slit maybe from the plastic shrinking.
Checking it with an ohm meter may give an idea if its bad.

I'm Guessing you have a problem with the auto Power input voltage selector.
If your running this from 220 single phase you should hear a relay or two kick in, the relays configure the supply voltage to the toroidal transformer. 220 or 440.
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  #3  
Old 09-25-2007, 09:23 AM
tom.jelly tom.jelly is offline
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re auto link: Thats what I'm hearing, about what went wrong. I'll pull the top board and have a look at the contactor for that. A bunch of the crimps look like that t-1, I'll replace all of those assuming I get it running. I suppose someone plugged it in to 460v and the machine did not switch to the lower voltage

ouch..

thanks
tom
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Old 09-26-2007, 04:31 AM
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GWIZ GWIZ is offline
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While your at it. pull the smaller board that has the melted cap on it and see if there's any damage under the board.

Maybe if your lucky the Rectifier bridge under the board has a hole burned thru it,
(Guessing that black thing that the power wires are screwed to).
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  #5  
Old 09-26-2007, 07:54 AM
tom.jelly tom.jelly is offline
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thanks for the info, it will be about a week til I can get to it, going to VIR for some vintage racing...

t
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  #6  
Old 09-26-2007, 01:17 PM
ventureline ventureline is offline
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You've blown SR1, 3 phase bridge rectifier. If you blown this you've also taken out resistor R7 (cause of smoke) One of your capacitors is likely shorted ( large blue 450Vdc units) as well as, one or two 20K resistors on the output board.

If you shorted a cap, one or both of your IGBT's is probably shot as well. Pull all the 5/16" screws off your out put board. (Side board where SR1 is) look for visable damage on VR1 and IGBT's 1 & 2. They are usually cracked in half with silicone oozing out of them.


These are easy fixes though not for an amateur to mess around with.

PM me if you want detailed information.

(Miller Tech)
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  #7  
Old 09-26-2007, 03:29 PM
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TommyA TommyA is offline
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OMG! We've been infiltrated by the Miller Board Techs come to get there members back. Quick run for the Hobart board boys, we'll cover your back.
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Old 09-26-2007, 05:09 PM
ventureline ventureline is offline
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There are lots of Miller CST Techs, If you want, I could equally say Lincoln Tech, or ESAB tech, or -dyne Tech. We are factory trained and provide waranty service for all ..
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  #9  
Old 09-26-2007, 05:39 PM
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Ventureline: Good to have your expertise here, it's good to know we have someone to help with the real sticky insides if we need help. Thanks for helping the member.
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  #10  
Old 10-02-2007, 05:58 PM
tom.jelly tom.jelly is offline
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Do you guys do component replacement on these boards, or just change out the boards?
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