WeldingWeb - Welding Community for pros and enthusiasts banner
Cancel
Create thread New Forums

Newbie needs help with Miller Roughneck 2E.

Jump to Latest
1 - 20 of 38 Posts
J

johnnybanzai

· Registered
Joined
·
38 Posts
Discussion starter · #1 ·
Serial # JF852939

So, I bought this thing with the understanding that it didn't make juice, and that turned out to be true.

I replaced the rectifier bridge, and got a 1000 microfarad 75 VDC capacitor installed.

No juice.

Now, if it were wooden I could make it work, and that's a fact, but it's electronical, so I'm in uncharted territory.

I did dig up a digital multimeter, and the outlets on the face are showing 1 or 2 VAC.

The welding lugs show the same.

I may not be using the meter correctly, either, but I sure would like to get this machine up and going.

Any ideas?

THANKS!
 
Discussion starter · #5 ·
Yep. The troubleshooting schedule is all complete, but no juice.

Thanks for the heads up on the capacitor. I think I got that mixed up with the part number off the Bobcat.

I replaced the rectifier, as I said before, but I checked the used one after the fact, and it seems OK.

It will likely be a week before I get the right capacitor in hand.

I'll give an update after it is installed.

Thanks!

John
 
#9 ·
Check the wire running to the condenser on the machine. That turned out to be the issue on my unit when I got it.

Sent from my Nexus 6P using Tapatalk
 
Save
Reply Quote Like Like
Discussion starter · #10 ·
Thanks, fellas!

I'm thinking the correct capacitor should be in hand by Wednesday, and I'll put all these suggestions into practice at that time.

Since I bought that machine, I have looked at many more. The face is in excellent shape, and even the paint is good.

I figure it's seen little use, so I'm hoping this mystery doesn't go too many more chapters, and I end up with a durable machine.

I'l let y'all know how it goes, and thanks again!
 
Discussion starter · #12 ·
New capacitor is in.

Everything still reads 1 volt.

guajilloweld03 said:
Test both cap and bridge rectifier before installing them. One time tested the bridge rectifier and it was bad, but did not check cap and it was bad. Then only replaced the bridge rectifier and the bad cap killed the bridge rectifier.
Click to expand...
Yes, I have always to remember to double-check the triple-check.:)

guajilloweld03 said:
Those parts are less $$$ from Allied Electronics and Mouser or a similar type Electronics store.
Click to expand...
I'll give your guys a try.

Denis G said:
Did you check that you're getting good contact between the carbon brushes and the rings? Also you should be able to read voltage between the wires feeding the brushes so that the rotor can produce a magnetic field.
Click to expand...
Thanks for the suggestion. I did check, and I can report that there is continuity from Wire #25 to Wire #26 through the brushes/slip-rings and revolving field.

The fuse is good.

The capacitor is OK.

The bridge rectifier. I take it that Wire #28 connects from the fuse holder to the Bridge Rectifier at the one corner that's cut off?

Hypervisor said:
Check the wire running to the condenser on the machine. That turned out to be the issue on my unit when I got it.

Sent from my Nexus 6P using Tapatalk
Click to expand...
I'm not sure what you mean. All the wire that I have seen in this machine is as new. Seriously.

I have chased both wires that connect to the capacitor and I have found no faults, but I'm not sure what you are telling me to check for.

cool air said:
Also check the fine adjustment control.Mine had a open winding in it and one of the two micro switches was bad.
Click to expand...
I am not aware of any micro-switches OR fine adjustment control.

Please advise!

I have been reading up on the idea that it needs to be 'flashed', which makes a lot of sense, as this thing has not made power in close to three years, if the previous owner is to be believed.

I've tried the drill method, with no success.

I wonder if there's anything I should know about the Roughneck 2E as regards placement of the battery leads or duration of the current?

Thanks, fellas.

I'm getting close, I just know it!
 
#13 · (Edited)
johnnybanzai said:
<snip>

I am not aware of any micro-switches OR fine adjustment control.
Click to expand...
See attached schematic from the Roughneck manual -


S1 is an electrical toggle switch accessible from the front panel. It has two positions one for "WELD" and one for "POWER".
S2 is a microswitch that is actuated by moving the throttle lever on the lower cowl of the engine. Full throttle sets S2 for "WELD" and flipping the throttle lever to the lower RPM sets S2 for "POWER" (115VAC). The machine is designed to either weld or work as a generator, but not do both. Both switches have to be set correctly to either weld or generate power.
The fine tune adjustment control is R1 on the schematic and is a potentiometer accessible from the front panel. For generator power it should be set to 100%. For welding it can be adjusted to fine tune welding current. Coarse welding control is accomplished by selecting the right electrode socket on the front panel.
 
Discussion starter · #19 ·
I may have a problem.

I mean, other than being a smooth-brained moron.

I am no electronics whiz, and the drawing has only 2 electronic components, anyway (counting the four diodes in the rectifier bridge as one component).

Because I am a smooth-brained moron, and because I always set the cover aside in its proper orientation - up side up, I never noticed that this machine has a copy of the circuit diagram taped to the underside!

!!!!!


This diagram, the same one I posted earlier:

Image



I do not know yet if this is significant or not, but the little symbol at the capacitor that looks like a '-' at 100% page size in my browser magically transforms into a "+" sign if I blow it up to 250%.

The diagram taped to the machine shows this discrepancy clearly.

I'm going to make that change, now.

Wish me luck!
 
Discussion starter · #20 ·
OK.

No joy.

I have had two occasions where I checked continuity across the rotational field and the meter read 26 ohms.

I think I must have botched those measurements.

I now have the machine up on the bench, and I managed to get the bell end off, removed the brush holder and checked continuity between the slip rings.

No continuity.

Each brush reads continuous through its respective lead up to the rectifier and capacitor (Yes, I disconnected the cap and rectifier before testing).

Neither slip ring is continuous to ground.

I am a determined little cuss, and I have read that this condition is usually due to a broken wire somewhere, and that if one can locate the break it can be silver-soldered back together.

I really want this.

I am having a really hard time figuring out how to get the rotational field the heck outta the machine, so I can examine it and fix it.

I mean, it's pretty clear that I have to split the generator from the engine, and I am seeing no obvious way to do that.

Any help?
 
1 - 20 of 38 Posts
About this Discussion
37 Replies
6 Participants
Last post:
johnnybanzai
WeldingWeb - Welding Community for pros and enthusiasts
posts
1.8M
members
82K
Since
2003
Community Forum for Welding Professionals and Enthusiasts To Interact and Learn - Free
Full Forum Listing
Explore Our Forums
Welding Projects & Pictures General Welding Questions MIG, TIG, Stick, And Oxy/Fuel Welding Machines - Tools and Cutting Methods Lincoln