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 :mad: 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,
http://img.photobucket.com/albums/v709/zippymbr/IMG_0481.jpg

http://img.photobucket.com/albums/v709/zippymbr/IMG_0482.jpg

http://img.photobucket.com/albums/v709/zippymbr/IMG_0482.jpg

http://img.photobucket.com/albums/v709/zippymbr/IMG_0484.jpg

http://img.photobucket.com/albums/v709/zippymbr/IMG_0485.jpg

[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

[Hobart Expert Bill]

Is this the AC or AC/DC Thunderbolt ?

First we need to make sure the switch is wired correctly.
I notice you said you have wired the switch up several differant ways. The two leads that go to the transformer each should have a fan motor lead luged to them, these should be attached one to each side of the top of the switch. The input lead has three wires, the ground attaches to the rear panel and the other two attach one to each side of the bottom of the switch.

What amperage is the circuit breaker that you are tripping ?

[ventureline]

Only 1 diode is likely blown, about a $30 part from Miller

[Zippymbr]

Is this the AC or AC/DC Thunderbolt ?

First we need to make sure the switch is wired correctly.
I notice you said you have wired the switch up several differant ways. The two leads that go to the transformer each should have a fan motor lead luged to them, these should be attached one to each side of the top of the switch. The input lead has three wires, the ground attaches to the rear panel and the other two attach one to each side of the bottom of the switch.

What amperage is the circuit breaker that you are tripping ?

My switch is wired with the 2 incoming leads on one side and the 2 outgoing on the other? I took off the red diodes and tested them with the Fluke. Pics to follow.

http://img.photobucket.com/albums/v709/zippymbr/IMG_0488.jpg

http://img.photobucket.com/albums/v709/zippymbr/IMG_0489.jpg

http://img.photobucket.com/albums/v709/zippymbr/IMG_0486.jpg

http://img.photobucket.com/albums/v709/zippymbr/IMG_0487.jpg

The first 2 pics are testing each pole of one diode, the next 2 are the second diode. One diode was 1.2 and 1.3 the other was 1.3 and 3.4

[84ZMike]

A diode is a one way only......looks like both are bad......are there only two of them? ......look on the side and let me know what they say and I'll see what I can come up with.
Mike

[Zippymbr]

A diode is a one way only......looks like both are bad......are there only two of them? ......look on the side and let me know what they say and I'll see what I can come up with.
Mike

I found 4 total. Which way should they be read? Red lead on the bolt area and black lead on the tab end? What reading range should they be in? There are 2 diffenent types of diodes with different numbers on the side of the bolt face.

[84ZMike]

You should have two for the pos.(+) and two for the neg.(-).... you should read resistance in one direction only and get the infinite symbol for the other.

[EdKing]

Make sure you are not touching the lead tips when you take the readings, the meter will read your body resistance. You should get a very high, if not open reading one way, and a much lower reading the other way. There should be 4 diodes as they use a full wave rectifier in most welders. Look for the diode/s that has a very low reading both ways as this indicates a short. The quickest way to check if its the diodes is disconnect the leads coming from the transformer to the diodes and tape them off so they don't make contact with anything, then turn on the welder and see if it trips the breaker.

Ed

[ventureline]

Really you don't and really shouldn't pull them all the way out of the rectifier just so you know which way they go back in.

A shorted diode will be 0.00 ohms

[Zippymbr]

Really you don't and really shouldn't pull them all the way out of the rectifier just so you know which way they go back in.

A shorted diode will be 0.00 ohms
Oh Snap! To Late! Noob LOL! I took a Pic for reference. I am still confused on the testing of the diodes now that they are out of the welder and the correct way to wire the switch.

[Zippymbr]

Is this the AC or AC/DC Thunderbolt ?

First we need to make sure the switch is wired correctly.
I notice you said you have wired the switch up several differant ways. The two leads that go to the transformer each should have a fan motor lead luged to them, these should be attached one to each side of the top of the switch. The input lead has three wires, the ground attaches to the rear panel and the other two attach one to each side of the bottom of the switch.

What amperage is the circuit breaker that you are tripping ?


I was tripping 2 50A. It tripped by arcing between the breaker and the neutral bus bar.:(