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Brady V
05-16-2008, 06:18 PM
Newbe here. I have a 225 Bobcat that only produces 70 volts at the 120 receptacles, and will strike an arc, but nothing warm enough to burn rod with, adjusting the fine amperage, coarse amperage didn't work. It doesn't work correctly in straight or reverse polarity nor AC. Idle and high idle do work correctly.

Any ideas?

Thanks,
Brady

on edit; I'll add a little more info, sn LA070084 and I believe it to be a 2000 model year

Zrexxer
05-16-2008, 06:34 PM
For starters, check fuse F1 as shown in Section 7-4 of the owner's manual, and then also check the brushes/slip rings. How many hours does the machine have on it? I've got a 2000 model also.

MAC702
05-16-2008, 07:20 PM
Does adjusting the fine and coarse amperage at least give you some kind of variability, even though it still doesn't get high enough?

Brady V
05-16-2008, 08:01 PM
For starters, check fuse F1 as shown in Section 7-4 of the owner's manual, and then also check the brushes/slip rings. How many hours does the machine have on it? I've got a 2000 model also.

F1 fuse checks out ok as do the brushes and slip rings. Meter shows 190 hrs and is original meter, well at least it appears to be anyhow.

Thanks for the quick response.

Brady V
05-16-2008, 08:02 PM
Does adjusting the fine and coarse amperage at least give you some kind of variability, even though it still doesn't get high enough?

Yeah I think it showed some variability.

Thanks also for your quick help.

ventureline
05-16-2008, 09:30 PM
Now, F1 is under the top cover, it protects a little bridge, is that the fuse you checked?

If thats ok, I'd be inclined to say you popped that red capacitor (C1) test it with an ohm meter to see if it takes a charge (your resistance will steadily increase).

Brady V
05-17-2008, 02:58 PM
Now, F1 is under the top cover, it protects a little bridge, is that the fuse you checked?

If thats ok, I'd be inclined to say you popped that red capacitor (C1) test it with an ohm meter to see if it takes a charge (your resistance will steadily increase).

Yep that's the fuse I checked. I checked my C1 capacitor (although mine is blue) as you described and it tests good.

Thanks for your ideas.

ventureline
05-17-2008, 05:34 PM
Well then I'd change out the little bridge, a common one is a 35 amp 800 volt, the voltage simply is the heat rating.

Also check your RPM, RPM is checked at the auxillary in frequency, " high idle" must be 62.5 HZ which would equate to 3750 RPM

Brady V
05-17-2008, 10:41 PM
Ok, I checked the HZ and it is good, but where do I find the bridge? :o

ventureline
05-17-2008, 10:56 PM
It'll be very close to that F1 fuse,it about 1x1x1/4" , black and 4 stake on terminals on it.

Brady V
05-17-2008, 11:41 PM
Ah ha, found it. Miller calls it a rectifier, SR2. I'll get one ordered Monday, hope this works.

Thank for your time ventureline.

MAC702
05-18-2008, 03:43 AM
A bridge is just a type of rectifier, so you're okay. We blew one of those recently on our Cigweld inverter, and even though you can't find a potentiometer in PNG to save your life, one of the supply stores carried bridge rectifiers. Amazing.

Brady V
05-27-2008, 05:29 PM
Just replaced the bridge, that didn't solve my problem. :confused::confused:

Brady V
05-27-2008, 09:43 PM
I just found that the R1 rheostat is burnt out, so I will replace it and go from there. I just don't know why that would cause low voltage through the 120 outlets, but then again these things could work because of magic for all I know. :D

ventureline
05-27-2008, 09:53 PM
Kinda thought you said that it was fine at first?

You kinda need R1 to make things go including the auxilary voltage.

Brady V
05-27-2008, 10:35 PM
Kinda thought you said that it was fine at first?

You kinda need R1 to make things go including the auxilary voltage.

Here is the question I was asked about it.


Originally Posted by MAC702
Does adjusting the fine and coarse amperage at least give you some kind of variability, even though it still doesn't get high enough?

Here is what I said;

Yeah I think it showed some variability


Sorry if somewhere I misunderstood a question, I appreciate your help none the less.

Is there particular reason a rheostat may fail?

Big_Eddy
05-29-2008, 08:37 AM
Age and corrosion. If you don't turn the dial, the copper contacts don't swipe across each other and stay clean. Corrosion = resistance = heat = a new one. Even if you always run the same rods at the same settings - turn those dials from time to time. That goes for the AC / DC + / DC - as well.

NMWelding
05-30-2008, 11:15 PM
I also have a 225 Bobcat. Good machine for the price. Only problem I had was when I tried to run stick on AC,[I had a problem with magnetic oilfield pipe] I could barely run 1/8 inch 6011 with the settings on maximum amps. I was also told to periodically move the dial throughout it`s entire range and also the selector switch. Not sure if this is my problem,it still doesn`t weld any better on AC. But after 4 years and never using this setting until now, maybe it is dirty or corroded in this range.

Big_Eddy
05-31-2008, 09:20 PM
When I bought mine it worked great. After a few weeks - I moved the selector switch - next thing I knew I had no gen output and it wouldn't weld even when I put it back to the original settings. Cleaned the selector switch contacts with some alcohol (they were filthy) and turned it back and forth about 10 times - now works perfectly again although I never have tried welding with AC. I'll have to give that a shot some time.

tailshaft56
06-02-2008, 01:36 AM
We get this contact lube at work. It's clear with a viscosity somewhere between 3-In-One oil water. The stuff does feel oily. I call it magic. It improves conductivity but doesn't short stuff out. Since it's primarily used for connectors I'm not sure how long it last on a rheostat coil or a contactor that sees intermittent contact.

I believe it's a 3M product.

Brady V
06-04-2008, 03:37 PM
I put the new rheostat on today, welder is operational again and welds so much nicer than my old worn Legend aead 200 LE. Sorry for leading some of you astray in trying to help me diagnose the problem, your help was very much appreciated.

Rest of the story, I purchased this gen/welder from a man my dad thought could be trusted as he knew him. Now I understand why this guy bought a new 250 bobcat and sold this one with 190 hrs on it. Oh, well it was a learning experience, and this guy just lost a potential buyer for his larger pieces of equipment that are worth far more than this welder. My complain isn't so much the having to work on this welder, as it is the lost time of getting to the field and finding out that the machine with me is down, and spending the time to go back and get the other Miller and limping it along long enough to get this one fixed. In the end I would have been just as well off purchasing brand new.

But it is fixed, so I am back to being :D:)