Beta-Mig 200 stops welding, won't feed wire

[vpnwiz]

Hi,

I bought an old Beta Mig 200 welder off eBay and drove out to PA last night to pick it up. The serial # is 81ws19275. I got home late last night and haven't put a new plug on to power it up. The guy I bought it from said he used it for a few years, then it quit on him and wouldn't feed wire any longer. When you pull the trigger it just clicks and won't feed wire. He put a new liner in it, and maybe did some other things to it but I don't know what. It's dirty as all get out, it came out of a corner of his barn and the case looks kinda sad but if I can get it working I am going to repaint it. The 5 lbs of dead bugs and dust was free at least

This is my first welder so any help on where to start looking would be appreciated. I'm in the Akron, OH area if that helps.

Thanks,
Patrick

[crawler]

I'm guessing the clicking sound is the contactor closing. I'd check the drive motor to see if that is the problem. Could the brushes be too worn?

[whateg0]

I'm not familiar with the Beta-Mig at all, but you should be able to check the voltage getting to the motor. I think you should also be able to check the OCV at the wire relative to the ground clamp. That would at least be a good starting point. I'm sure somebody here has some experience with the Beta-Mig and can give some more pointed advice.

Dave

[Mike W]

The Beta-Mig was built to last. Mine is still working after 20 years. The motor voltage is 20 volts max. The wire speed control is a variable transformer. The output goes to a full wave bridge to get DC. There is also a k2 relay contact and a 1/2 ohm, 30 watt resistor before the motor.

Check the DC voltage output of the welder. From the ground clamp to the gun connection. On low range (jumper inside front corner) with switch on 9 or 8, you should see approx 26 vdc. Also, check the contactor contacts. The contactor supplies 220 to the main transformer for welding and also the power for the drive motor.

Clean it out good. There may be dirt in the 2 small relays. Let us know what you find out.

[vpnwiz]

Thanks guys, Mike you said to check for around 26vdc at the gun connection. This may be a totally ignorant question, but what do you mean by "gun connection"? Do I put the meter between the electrode at the end of the nozzle and the ground clamp?

I wouldn't be surprised if the case was full of dirt inside. I'll be taking it apart tonight for a good cleaning.

Also a giant thumbs up to the Hobart/Miller literature people, they found a manual for this machine and already sent it to me!

I'll post back with what I find tonight. If you could clarify where I should meter I would appreciate it.

Thanks,
Patrick

[Mike W]

You could do that or just measure at the lug that the gun power cable attaches to. Other meter lead to the ground connection. That welder is rated at 200 amps with a 60% duty cycle. Some newer units would melt trying to keep up.

[vpnwiz]

OK, here's what I found. I took the case off and there was a thick coat of dust inside but that was about it. I blew it out with an air gun and wiped everything down.

I get a good DC measurement between the lug and the clamp. With it on low and the handle around 2, I get ~17Vdc. With the handle around 7 I get ~23Vdc.

I can see the contactor and relay moving - there was some arcing at first though it looks like it went away. Metering the leads going into the motor gives me 0 volts. Looks like the motor leads go to the full wave bridge(?... oh, I went and looked up what a rectifier does) and the resistor. That's where I was metering.

At this point I think I should begin troubleshooting backwards, find out where there's voltage and then figure out why the next step doesn't have it. I'll check the output from the wire speed transformer and see what I get. Assuming that checks OK, how do I verify the rectifier is OK?

Thanks,
Patrick

[whateg0]

...Assuming that checks OK, how do I verify the rectifier is OK?

Thanks,
Patrick

I'm not sure how the rectifier looks in your case. They come in many styles. However, if there are any markings on it, there should be 2 wavy markings and maybe a (+) and (-). The wavy ~ are the ac coming in. Refer to a previous post for the correct voltage there. The (+) and (-) will have the DC output across them, or at least they should. It seems that you probably have 0VDC there unless you have a bad connection or broken wire between the rectifier and the motor. Again, not having a schematic, that's about as specific as I could get.

Short version - check for an ac voltage at the ~ marks and a DC voltage across the +/-.

Dave

[Mike W]

The rectifier has one AC connection to term 7 on the transformer. The other rectifier AC connection goes to the variable tap on the wire feed transformer. See if you have AC voltage across these two connections.

There is an F2 fuse before the rectifier. See if there is AC voltage across the two terminals of the wire feed speed control transformer. The 3rd terminal varies the voltage as the wire feed is varied.

If you have input to the wire speed variac but no output, it would have an open winding.

[vpnwiz]

OK thanks guys. I think the wire speed control transformer is going bad. When I was testing on the AC lugs of the rectifier I would get 0 volts. Then if I would spin the wire speed control around sometimes it would "hit" and go up to ~15 or ~18Vac. But then it would go away pretty quick, after a few seconds.

I've attached the wiring schematic from the manual as a PDF. I tried testing the transformer, maybe it's because it's going bad but I couldn't really get a good reading, it was all over the place.

<just saw Mike W's reply>

OK Mike I was going to do your tests but I noticed that the input to the rectifier is not coming from term 7 but from term 4. Before I go any further, should I put it back to term 7?

Thanks,
Patrick

[vpnwiz]

I think now we are getting somewhere. I checked for Vac from term 4 to both pre- and post-fuse coming from the wire speed transformer. Standby it was around 1.4Vac. Pressing the trigger it went down to about .6Vac.

Checking both input terminals of the transformer show 20Vac when the trigger is pulled.

So should I move the other input for the rectifier from term 4 back to term 7 where the schematic shows it should be? Or just get a new wire speed transformer? And if I just need a new wire speed transformer, is it something I need to source from Hobart or can I get it somewhere else?

Thanks for ALL the help.

Patrick

[Mike W]

I would leave it there for now. The contact of the variable transformer is a common problem area. You might look at that. As you turn it, it makes contact on the windings to change the voltage.

You can fix these with easy to find parts. Try setting the voltage at pos 8 or 9 on the low tap once you fix this problem.

[vpnwiz]

Well... I got the drive motor to work! I noticed the back of the wire speed transformer windings were all glossed up, so I took some sandpaper and rubbed it off til the copper showed through. The drive motor fired RIGHT up!

Now it looks like I need to fix the wire feed part itself... the wire isn't lining up in the groove on the lower roller. I'll check the manual for the info on that and if I need help make another post.

THANKS AGAIN FOR ALL YOUR HELP! I CAN'T WAIT TO MAKE SOME SPARKS!

Patrick

[crawler]

Well... I got the drive motor to work! I noticed the back of the wire speed transformer windings were all glossed up, so I took some sandpaper and rubbed it off til the copper showed through. The drive motor fired RIGHT up!

Now it looks like I need to fix the wire feed part itself... the wire isn't lining up in the groove on the lower roller. I'll check the manual for the info on that and if I need help make another post.

THANKS AGAIN FOR ALL YOUR HELP! I CAN'T WAIT TO MAKE SOME SPARKS!

Patrick

Good work...

[Mike W]

Interesting, be careful not to let 2 windings short together. Try the wire speed between 3 and 4. I run .035 wire and C02 gas most of the time. I have a lot of load readings if you are interested. Setting up the drive wheels should not be a problem for you.