Mig welder wire feeder controller board not working

[.RC.]

So I decided to turn on my older transformer mig welder that has sat idle for a couple of years, it was working fine when last switched off.  The machine powers up but the wire feeder is dead.  I have wriggled wires and measured a few voltages and the board is getting power but nothing happens when I pull the welding trigger.

The board gets fed 24V AC power, and I have gone so far as measuring 34V on the board after the bridge rectifier.  The board does multiple things.   When you pull the trigger on the welding handpiece, it should send voltage to a gas solenoid to turn the gas on.  It should send voltage to the wire feeder motor to feed motor, which I suspect is via PWM, it also send voltage to turn on a main contactor for the welding transformer.

The board has inputs of a potentiometer for the wire speed, a burnback potentiometer  that means after the trigger is released the wire feed is cut the welder still welds for a fraction of a second more. and a toggle switch to control what happens when you pull the trigger on the torch, either a simple on/off, press once for on and press again for off.

The board seems in good condition and there are no obvious faults, all through hole, double sided tracks.

I am not sure where to start trouble shooting due to my inexperience.  I can solder desolder through hole stuff OK. Have multimeter, DC power supply and oscilloscope on hand.

Since nothing works I would suspect the power supply side of the board.  I am sure it is repairable especially as I assume it is all analogue.

[floobydust]

Quick eyeball check - the relay has one set of contacts that look destroyed. The power transistor bottom left looks like it's run hot a lot,  poor heat transfer to the heatsink.
A real mix of brands of electrolytic capacitors, I would replace the cheap ones. 1999 was a while ago.

[xavier60]

Where was the 24VAC measured? There appears to be a PCB mounted control transformers supplying multiple regulators.
EDIT: Does the trigger switch have proper connection to the PCB?

[xavier60]

What feeds the PCB transformer?

[TERRA Operative]

What is the brand and model number of the welder and feeder?
I see Cigweld on the PCB, so I miigghhttt have a manual or even service manual for it.

[.RC.]

Thanks for the replies, Here is an updated mirrored photo with some of the pin outs identified.  Also have a photo of the back of the board which the pin outs will line up with the mirrored photo.

The relay points are a bit burnt, but I did test it with the bench power supply and it still works.

The welder is a 250SE, but the wirefeeder is separate, it is a 2R model 705995

I have tested the torch trigger, no issues there.

[coppercone2]

i wonder if they have a hand crank fed mig some where

the deep future of welding is a hand cranked super conductive dynamo that both feeds wire and generates electricity to power the welding process, for body repair in the far corners of the galaxy (New Pakistan, 12,101 A.D)

[TERRA Operative]

Here's the Service manual for the feeder and other documentation I could find.
(Linked here in my Google drive too, the welder service manual is too big to upload here)
If you let me know the 6 digit model number of your welder, I can check if I have the exact manuals. I assume it is probably 706118?

I see the schematics for the wirefeeder, including board level components etc are in the service manual which is nice.

Page 17 has the voltages, and from page 18 has a troubleshooting guide that should help narrow down the problem a bit.

I would first disconnect the feed motor from the control board in the feeder and briefly apply voltage (24V) to ensure it is not jammed or seized, and give the motor a sharp tap with the handle of a screwdriver to loosen it up if something is stuck. Also check the brushes aren't worn or stuck.

As an aside, make sure your rollers are free to turn (grease the shafts they spin on), and the gears aren't worn as they can start to jam if the teeth are badly worn. Also make sure the wire path and grooves in the rollers are kept perfectly clean for best grip on the wire.
Poking the wire through a foam earplug before it enters the feeder assembly is a cheap trick to keep the wire clean as it goes through the rollers.

[coppercone2]

there has got to be a better filter then a foam ear plug. maybe a fine nylon brush?

its such a dodgy construction worker hack

I don't like it because theoretically something can get stuck in the foam and scratch up the wire, and it can soak up grease and smear it on etc. I feel like a nylon brush would brush off debris and result in cleaner wire

there must be a more professional engineering solution to this using better hardware

[.RC.]

Here's the Service manual for the feeder and other documentation I could find.

Thank you so much.  I did not expect this sort of information to be available.  When I bought this welder new I did not even get a manual with it.

I think i should be able to do something now, probably let the magic smoke out somewhere.

[TERRA Operative]

there has got to be a better filter then a foam ear plug. maybe a fine nylon brush?

its such a dodgy construction worker hack

I don't like it because theoretically something can get stuck in the foam and scratch up the wire, and it can soak up grease and smear it on etc. I feel like a nylon brush would brush off debris and result in cleaner wire

there must be a more professional engineering solution to this using better hardware

The 'official' way is a lightly oiled felt 'slug' held on with a metal clip.
https://www.google.com/search?q=mig+wire+cleaner&udm=2

Thank you so much.  I did not expect this sort of information to be available.  When I bought this welder new I did not even get a manual with it.

I think i should be able to do something now, probably let the magic smoke out somewhere.

The benefit of buying a quality brand instead of a cheap Chinese no-name import.

And I archived all the manuals from when I was in the welding and cutting equipment repair game.

[.RC.]

I believe I have found the problem.  Could not work out why I could not get any of the DC voltages anywhere and why I could not get continuity to the isolation transformer from one of the AC input legs.  So I suspected it was a power supply issue.

Removing the isolation transformer revealed the problem.

Running a jumper wire and everything is clicking as it should.

[coppercone2]

wow I don't like that attachment. I thought the weld wire would have to be clean from oil. I guess its not like TIG were they have you religiously clean it. I suppose that feeder might be oiled too lol.

[.RC.]

I have been doing the ear plugs on the wire for quite a few years now.   I did at first have those special foam things, but earplugs are much cheaper.  I do not so critical structural welds so I do put corrosion inhibitor on the wire as a roll may last quite some time.  I cannot say I have had porosity issues because of it. 

[TERRA Operative]

Yeah, basic, non critical MIG welding on mild steel is pretty forgiving. I never really understood why some people end up with no penetration on their bird-poop welds....

TIG does need a clean surface, but there are welders that provide cleaning settings (AC balance IIRC?) especially for aluminium alloys etc, but nothing beats a pre-cleaned surface.

[coppercone2]

I imagine  the degree of porosity added by some oil would require x-ray to find, it must be very minor.

Not that I care, but you know, boeing might be using mig welders for airframe repair or something

But I do have the mentality that a non professional will benefit from the best possible conditions because the work you put out without it being basically a trade job might be so marginal in some cases that the extra steps keep it barely in line. If I can get some extra help from essentially a passive system I will take it, I just don't have the time and inclination to always do a practice bead and stuff that a pro would get paid to do

[xavier60]

A little off topic but wire feed related. Since repairing a no wire feed problem with my brother's WIA 250i, it now will stop feeding if an arc doesn't strike within a second of pulling the trigger. Seems to be a feature that has been activated somehow, but no mention of it in the manual. Not a problem in practice.

[.RC.]

Yeah, basic, non critical MIG welding on mild steel is pretty forgiving. I never really understood why some people end up with no penetration on their bird-poop welds....

I actually found it hard to do a bird poo weld with a mig.   What it is easy to do it do a visually fantastic looking weld that has zero fusion to one side.   I have also found cold mig welds on commercially made stuff. The bead stands proud like your nipples on a cold morning.

Mig welders because they are more complex to get the settings right, with volts and wire feed and gas type or gasless or dual shield has opened a whole new level of crap welds.  At least a stick weld looks crap if it is crap and starting out stick welding I did a lot of crap welds.

The old days your 15a socket melting (yes I melted a few of them) AC transformer stick welder had one knob to adjust (well some were flash and had 2 OCV settings), and everyone was running 6013 rods.  Life was simple.

Of course one quirk for Australia that has gone full short bus on regulations.  Dodgy Darryl at his home with his $150 mig welder and a roll of flux core and ten minutes welding experience can weld up a trailer to tow behind his car and get it registered no problems at all.

[TERRA Operative]

A little off topic but wire feed related. Since repairing a no wire feed problem with my brother's WIA 250i, it now will stop feeding if an arc doesn't strike within a second of pulling the trigger. Seems to be a feature that has been activated somehow, but no mention of it in the manual. Not a problem in practice.

Apparently, the wire should feed normally for 5 seconds, then run at full speed (for feeding wire down the MIG Gun etc).
Might be an issue with the current sensing somewhere, but I unfortunately don't have access to the WIA service portal anymore to get the full schematics (if available).

[bill_c]

I would replace all those capacitors, one ore more is leaking.  Make sure you clean the board well.

[.RC.]

You mean just the electrolytic ones or all of them? As there are quite a few rectangular ones and ceramics.

[TERRA Operative]

Just the electrolytic capacitors, film and ceramic capacitors very rarely go bad.

[.RC.]

OK, At least with the good service manual, I can order new ones from AliExpress in advance. 
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Sorry I meant Mouser/Digikey/Element14, etc.