Millermatic 250MP Technical Manual

I don't have the tech manual, but if you follow the traces on the main board for the motor output back to the motor driver, It is a good bet that the power device that drives the motor is toasted. There might be some kind of interlock on it, but usually the highest power handling device in a circuit is the first thing to fail. You can do a lot of reverse engineering with manufacturer data sheets for the parts in the circuit.

Look at power supply voltages around the driver circuit. If they look sane, and you can see all the inputs to the circuits (from the data sheets) behaving in a way that makes sense, I would swap the output devices.

Good Luck, BobH

This sounds like the _Technical Reference Manual_ for a computer I used quite a bit back when. It had the full schematics for the main system board, and various plugin-boards (no not PC compatible at all), but two things had no such schematics. The card in the video monitor, and the switching power supply.

Both were made by other companies, and I don't think that this company even *had* the schematics. They just specified what they wanted it to do (and the pin locations for the power supply connector) and it arrived from the manufacturer. End of game.

The tech manual may not have those schematics, either. But it may have more troubleshooting info, so you could verify where the problem really is. It sounds like it is in the wire feed, or perhaps some sensor which verifies that the wire is there before turning on the motor.

No such luck here. Sorry.

Good Luck, DoN.

You might try a two-step search. Look for the tech manual and check the previews offered by the fee-based manual sites. That might disclose the document number of the tech manual, quite possibly same as the owner's manual, but with a TM prefix instead of OM. Then try a web search for that number.

The Miller forum folks are helpful to a point, but behave as if there's a lawyer sitting on their shoulder. Since it's a company forum, likely that's the case.

bob prohaska

Thanks for the advice. I'm a retired two-way radio tech with lots of other dabbling in devices. That is what I've been doing so far. Internet access helps a lot nowadays. Beats looking through a shelf full of old IC books anyday :) Tedious work and tail chasing though when you can't see how everything kinda works and links together. I sorely miss the multi-color board layouts, circuit theory and diagrams in the good manuals I used back then...

Figured this to be a long shot but I might get lucky :)

Does Miller have a repair service for the board? If not, their attitude is: "You can't get a new board & we won't fix it, so the welder is junk"?

They weren't given any options for any price from what I understand. I didn't find anyone selling the board nor any place offering to repair it (neither did he). The main circuit board is still available for ~$510 and I found at least four places with offers to repair that board. It seems the main board is also used in the Syncrowave. Probably why it is still available...

Kind of sad, the machine is circa 1996.

I'm not so sure it is really bad. I'm having problems with the main circuit board too. Without seeing how the two boards interface together I wouldn't yet condemn it...

Given the price of their equipment, that's a horrible attitude for blue to have. I wonder how many people go red as a result.

Thanks for the reply, advice. I'll pass this on to my friend if I fail to get it fixed. It is a personal machine so it isn't stopping production or slowing business options.

The technology used in this machine is stuff I used to work with, repair. I'm familiar with all of it just not in how it is being used. The lack of schematics and board layouts for the main and microprocessor circuit boards is the biggest time suck, annoyance...

You maybe right with that insight. I scrounged a tech manual for a newer model and that description fits. Lots of test point voltages but still no board schematics for the microprocessor area...

Thanks for the reply and thoughts :)