Broken Thunderbolt Noob!

[Zippymbr]

I was given a Miller Thunderebolt by a good friends father last year and can't get this thing to work. It sat in his barn for 10 years only being used a few times. He brought it here to NC from Indiana to teach me and some friends how to weld. He was a master welder with FORD for 25 years. We never got the thing to turn on while he was in town. It worked according to hime before he left. I found the power switch was broken and tracked one down and replaced it. Now it will come on for a millisecond and then arc/trip the breakers. I have tried a few different ways to wire the switch up with no avail. Diodes? short? improper wiring? Help Thanks

Matt

[84ZMike]

Were in NC are you? You can find the owners manual here http://www.millerwelds.com/service/ownersmanuals.php

[Zippymbr]

I'm in Durham not too far from the southpoint mall. I got the manual in PDF but it is not as helpful as I thought it would be.

[ventureline]

You probably have a shorted diode. It should come on for a mili-second buzz and kill the breaker

[Zippymbr]

You probably have a shorted diode. It should come on for a mili-second buzz and kill the breaker

That is what it seems to be doing. I have a Fluke DMM but have read that is not the best way to test the diode?

[ventureline]

Take the nuts off the diode pig tails to isolate the diodes and check with a diode checker.

[84ZMike]

I make service calls out your way from time to time...... if you do wind up needing any parts let me know as I know an old guy that could have some of the stuff you need for lots less than you would pay at any LWS / repair center around......and if needed my LWS's repair guy lives close so I could drag it to him to check it out....
Mike

[EdKing]

You can check the diodes with a DMM. Isolate the diodes like ventureline said, then measure the resistance across the diodes, you should get a different reading on the diode when you reverse the DMM leads. Look for a diode/s that is shorted (very low resistance reading) and that will be the bad diode/s.

Ed

[Zippymbr]

I make service calls out your way from time to time...... if you do wind up needing any parts let me know as I know an old guy that could have some of the stuff you need for lots less than you would pay at any LWS / repair center around......and if needed my LWS's repair guy lives close so I could drag it to him to check it out....
Mike

Thanks for the offer, I was going to ask if there was someone who could fix it in the area. I will check the diodes as per Edking and see. I would love to get this up and running so I can stop borrowing My friends Hobart 210 . I 's sure I will need some parts.

[EdKing]

If the Thunderbolt is built anything like the old Lincoln IdealArcs (big tombstones), you should be able to disconnect the DC portion and still use the AC welding capabilities. When my brothers went bad we did this so he could still weld while he was waiting for the parts to arrive.

Ed

[Zippymbr]

If the Thunderbolt is built anything like the old Lincoln IdealArcs (big tombstones), you should be able to disconnect the DC portion and still use the AC welding capabilities. When my brothers went bad we did this so he could still weld while he was waiting for the parts to arrive.

Ed

Looking inside it looks like I can just unhook the DC plugs and it will just run in AC mode?

[EdKing]

You will have to unhook the diodes and isolate the leads that connected to them to the transformer, the sides of the diodes away from the welding leads.

Ed

[Zippymbr]

I tried to find the diodes All I found were resistors. You can see in the first pic that I unhooked the resistor and tested it both ways at 4.05 OHM. Here are some pics,

[84ZMike]

Look to the right in the 1st pic.....the leads with the red insulation on them that area about 1/2" thick...those are your diodes.....one end has a bolt thru it and the other has a nut on the backside....

[EdKing]

The diodes might be listed on the parts list as the rectifier, which is 4 diodes to convert the AC current to DC current. The diodes will usually look like bolts going through the plates that the positive and negative leads are attached to. Looks like somewhere around 16-19 and 27-29 on the parts diagram. There should be some leads connecting from the main transformer (14 on diagram) to those plates. If you disconnect those leads and isolate them (tape the bare end with electrical tape) you should be able to use the AC portion of the welder, if the diodes are actually the problem. I would only use that as a temp fix until you can get the DC portion fixed, as the DC welds much smoother and nicer than the AC.

Ed