Miller AEAD200 Low voltage

[Jnjjunk]

Hi everyone, I recently acquired an older AEAD that has been sitting in the back of a welding shop for years. Serial number JC602382. I got it running, it needed the fuel pump rebuilt. I went to go check for voltage at the AC outlets and found that I only have around 1 volt there. Checked the welding outlets with the machine idled up and I also only have around one volt there.

I've been crawling all over this forum trying to hit all the trouble shooting posts about these welders and I still haven't found the cause of this problem. I checked the diode in the side of the machine and that seemed to check good. Also cleaned the bands on the two resistors but no changed after that. Those seemed like the two major causes that I came across here. I've also tried grabbing the throttle linkage and running it past 3000 rpm a couple of times but that did not help either.

I appreciate any insight anyone might have

[Bushytails]

First things to check are the brushes and slip rings. The slip rings should be clean and shiny, and the brushes should move freely and spring into the slip rings tightly. If that doesn't fix it, measure the voltage on the brushes to check for the next step.

[Jnjjunk]

The brushes move freely. The slip rings are fairly clean, you can see where the brush has been rubbing on them. I'm not 100% certain how you check voltage at a brush, but I had very little (<1 volt) at all of them

[Bushytails]

Measure the voltage between the two brushes.

[Jnjjunk]

I have 3 brushes on this machine, but I checked for DC voltage between all of them and had less than a volt. I appreciate the help. I have some electrical knowledge but never dealt with generators before.

[guajilloweld03]

Get a copy of the manual from millerweldsupport and check/test F1 and SR1, search for this generator manual which shows how to test components.

[welderdoc]

if this machine has been setting around a while not being used you may have to excite it. check f1 and sr1 as stated above first

[Jnjjunk]

Im going to check sr1 tonight, this machine does not have any fuses in it, Not that I could find or see on the electrical diagram

[guajilloweld03]

My bad, Fuse F1 is on generator only models

[Jnjjunk]

Ok so looking at the schematic I thought sr1 was going to be a bunch of diodes. And it may be but not sure what I'm looking at. As far as I can tell it's this big chunk of aluminum. Just want to make sure I'm looking at the right thing

[Bushytails]

Sorry for not helping more... life has been keeping me really busy.

It would be SR2 you need to check, the exciter rectifier, not SR1, the output rectifier. Checking D4 and its connection to the power switch would also be a good idea.

I haven't worked on that exact machine, but SR2 is probably in the little square aluminum heatsink on the bottom right of your image. It should test as four diodes - but it sounds like you already checked it?

D4 goes from the power switch to the excitation winding, to supply 12V to the slip rings when the switch is on. Check the switch is good, the diode is good, the wiring is connected, and the ground from one of the other slip rings to the body is good.

[ryanjones2150]

Have you tried the old turning the drill motor backwards trick? It works like a charm on regular generators every time.

1/2” drill motor, plugged into the generator, set to forward direction, breaker closed, pull the trigger on the drill motor and turn the chuck backwards by hand. Be ready, if it excites the field, that drill motor will take off, so don’t use a glove or put anything in the drill chuck to hold on to if you like your fingers intact. Like I said, it works on generators, don’t see why it wouldn’t work on this.

[Jnjjunk]

I have not tried the drill trick yet. I did it on my old pto generator and it worked like a charm.

checked sr2, all didodes checked the same. Around .6 volts so i assume that's fine. I was checking voltage at d4. I had battery voltage on the switch side. No voltage on the other side of d4. So I pulled d4 out and I'll be dam no continuity. If you wiggle it around and twist it, it occasionally makes a connection. So I'm hoping that's the problem. Even though I know i checked it a couple weeks ago and I'd swear it checked good.

I really apperciate everyones help. I dont really have a use for the welder so I'm not in a hurry to get it going. Just thought it'd be nice to have around for when you do need it.

[Jnjjunk]

I think this should be a suitable replacement for that diode. Manual said 3 amp 1000v, other then that I don't really know what the rest of those specs are on these diodes

10PCS 1N5408 Rectifier Diode 3A 1000V DO-201AD (DO-27) Axial 5408 3 Amp 1000 Volt: Amazon.com: Industrial & Scientific

[Bushytails]

Sounds like you found your problem! Just about any 3A or larger diode will work, or you might be able to repair the connections to yours, depending on where it broke.