I need some welding critique!
#286
I'm a little late to the party (been browsing this thread off and on and enjoying reading your adventures!), But I would recommend doing a pre-power check before plugging it in again, if you are comfortable with a DMM (digital multimeter).
If you decide to open it up and start working on it, BE VERY CAREFUL! There is a lot of power stored inside the capacitors and the possibility of electric shock, or being hurt by exploding components is very real. Always wear safety goggles when the cover is off, and test the main capacitors to ensure they are discharged before touching anything else inside. When a part fails, it can explode and send debris flying faster than you can react and get away from it.
If you decide to open it up and start working on it, BE VERY CAREFUL! There is a lot of power stored inside the capacitors and the possibility of electric shock, or being hurt by exploding components is very real. Always wear safety goggles when the cover is off, and test the main capacitors to ensure they are discharged before touching anything else inside. When a part fails, it can explode and send debris flying faster than you can react and get away from it.
#287
My guess is that you have a problem with display board PC3. It seems unlikely that the thermistors on both sides would fail at the same time, unless it was caused by failed IGBTs. I would definitely recommend going through the pre power checklist before replacing any parts based on the help codes.
#289
#290
#291
Yes, I do have one. I don't like buying a little El cheapo ones, I've got a pretty decent one.
#292
Leave the machine unplugged for a day before working opening it. That will give the capacitors a chance to discharge on their own. Then, when you first open it, set your DMM to DC volts and test across the terminals on each input capacitor. If any significant voltage is present (more than a few volts), leave it for longer before working on it.
#293
Out of curiosity, what is your machine's serial number?
#294
f you decide to open it up and start working on it, BE VERY CAREFUL! There is a lot of power stored inside the capacitors and the possibility of electric shock, or being hurt by exploding components is very real. Always wear safety goggles when the cover is off, and test the main capacitors to ensure they are discharged before touching anything else inside. When a part fails, it can explode and send debris flying faster than you can react and get away from it.
#295
materthegreater, you inbox is full! He is my last message to you.
I believe I found a short on IGBT PM1. In your book it would be section 7-5. Instruction number three. Check C1 to E1, and C2 to E2 on PM1 and PM2 for no less than 100 ohms. 0 ohms indicates a short. PM2 passed with flying colors. PM1 has 0 ohms between E2 and C2. What does this mean? Bad board?
I believe I found a short on IGBT PM1. In your book it would be section 7-5. Instruction number three. Check C1 to E1, and C2 to E2 on PM1 and PM2 for no less than 100 ohms. 0 ohms indicates a short. PM2 passed with flying colors. PM1 has 0 ohms between E2 and C2. What does this mean? Bad board?
#297
I also found this sitting underneath PM1. Looks like a broken part of a component.
Also, when following the pre-power checklist from the technical manual, it had me test the capacitors. I was not 100% sure how to do this. The book said to test all three capacitors for a short. So I assume this meant to test resistance on each capacitor individually from one post to the other. If I did this right, the tank capacitor has an open circuit. Here's how I tested the capacitors.
I tested for ohms on every setting that my meter has. Not on this particular capacitor, but the one big one down to the right that is not shown in this picture was the shorted one. It is the tank capacitor. It showed no resistance.
I also tested all four diodes on the PC-2 board as instructed by the manual. Three out of the four read either way too high or way too low.
Also, when following the pre-power checklist from the technical manual, it had me test the capacitors. I was not 100% sure how to do this. The book said to test all three capacitors for a short. So I assume this meant to test resistance on each capacitor individually from one post to the other. If I did this right, the tank capacitor has an open circuit. Here's how I tested the capacitors.
I tested for ohms on every setting that my meter has. Not on this particular capacitor, but the one big one down to the right that is not shown in this picture was the shorted one. It is the tank capacitor. It showed no resistance.
I also tested all four diodes on the PC-2 board as instructed by the manual. Three out of the four read either way too high or way too low.
#300
Good for you for finding the blown off piece that has the part number CM100DY-12H. But don't bother looking for that part number.
Miller discontinued those particular IGBTs. Look no further than your own machine for the reason why.
Miller re-specified a different IGBT as a replacement, and the new IGBT is a CM75DUM-12F.
You need to replace ALL of the IGBTs, not just the one that exploded. The kit from Miller is $900.00.
I've seen eBay specials from LongShen in China for as little as $25.00 each.
If it were me, in your shoes, I'd button the cover back on your Miller XMT304, and set it aside. Write down some notes on these part numbers, print out a few photos you took of the guts, stick your notes and photos in an envelope, tape it to the machine, and get back to learning how to weld with the AC transformer that you already bought and paid for, that is rock solid, dead simple, doesn't have any fancy whiz bang, and I do mean "BANG!" electronic components that are expensive to replace... and get back to welding.
I never ceased to be impressed with what you take on, but you can replace every one of those IGBTs, and still find that you need to also replace one of the circuit boards too.
Before becoming a welding machine repair technician, get confident with the AC machine that you have, and as you get into it, you may find that another DC machine, at very low cost, manifests itself into your orbit.
That being said, count your blessings to have Glen by your side on the XMT. MatertheGreater's assistance is yet another manifestation of goodwill!
So many choices!
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