Lincoln 185 compact mig

[Seath]

Bought this brand new 9 years ago and has had a fair bit of use however it stopped working all off a sudden. Everything seems normal, fan running, relay shuts on trigger pull but no wire feed or arc. The wire feed motor runs ok on an independent 12v supply so I thought that this could only be a problem with the PCB as it seems to receive 230v, but no 12v output as far as i can determine with my dvm. I ordered a replacement PCB for £65 but this has made no difference so I am at a bit of a loss. Any ideas please?
BTW The multiple cables that run from the rotary switch down to the main transformer have gone gloopy and stick together see pic below. I was reassured by the welding servicers who supplied the pcb that this is normal. Any comments there?

 

[Richard.]

@bwservices knows his Lincoln’s pretty well.

 

[eddie49]

The wires from the transformer to the rotary switch are enamelled or epoxy-coated copper, and then sleeved. The sleeving has gone sticky and is dusty, but that is not going to cause any problem.
The PCB is very basic, it seems to have just a transformer and a diode on it, not much else. Are there any other electronic components - such as transistors that would provide a decent motor speed control - near the wire speed control potentiometer?
The main contactor pulls in when you press the torch trigger, does the gas solenoid also click in?

 

[bwservices]

when you say the relay activates on trigger pull,is that the one on the pcb or the main contactor?
it could be a thermal trip,faulty over temperature sensor in the main transformer or rectifier.

 

[Greg05]

have you managed to get this fixed? seen this listed on ebay for £1000 buy it now but with no mention of any issues....

 

[eddie49]

This Forum link refers to a similar issue - same machine, same fault, PCB also replaced with no solution, turned out to be a failed main transformer:
https://www.mig-welding.co.uk/forum/threads/lincoln-185-compact-mis-behaving.52242/

 

[Seath]

Sorry should have said I pinched that photo from ebay as same machine as mine but more recognisable!

Yes contactor closing not relay my poor description

I'm not sure if the gas is working will check that today, its been out of action for so long I forget.

Thanks for the ideas on what to check and that link looks very helpful

 

[Seath]

Thanks for your patience, just got back to looking at my welder and have these updates. The wire feed and infact the arc work only on power setting 6 off 6, although not at with the wire speed you would expect from that setting. The gas valve is opening fine.
Any thoughts and insights would be appreciated Duncan

 

[eddie49]

The rotary switches that control power settings can fail. They can get stiff to turn, jam, contacts inside can burn or break off, screw terminals can get loose or the wires can burn. Be very wary of trying to fix the internals of this type of switch, they tend to spray springs, contacts and ball-bearings all over your garage floor when opened up.
However, on this Lincoln Electric model, the thread I linked to earlier indicates that the solid copper transformer wires have a tendency to break just before the screw terminals at the switch:
https://www.mig-welding.co.uk/forum/threads/lincoln-185-compact-mis-behaving.52242/
I would suggest unbolting the switch from the front panel and then examining all the wire connections and links very carefully, also where the wires go back into the insulating sleeving. Something may be loose or have broken at or very close to the switch.

 

[Seath]

After contacting Lincoln with my problem, they pointed me toward the transformer and rotary switch. so today I unbolted the main transformer and carefully slld it out but no obvious breakages, unless the fault is under the insulation etc. I also checked the rotary power range switch. I'm afraid I did not take head to warnings and disassembled the switch, that was an hour of fun putting it back together, only to then realise, the contacts can be accessed with switch intact, deep joy! but it all seems clean and new looking inside and now with cleaned contacts but the result of this session has made no improvement sadly, still only getting action on power setting 6.

 

[Seath]

After contacting Lincoln with my problem, they pointed me toward the transformer and rotary switch. so today I unbolted the main transformer and carefully slld it out but no obvious breakages, unless the fault is under the insulation etc. I also checked the rotary power range switch. I'm afraid I did not take head to warnings and disassembled the switch, that was an hour of fun putting it back together, only to then realise, the contacts can be accessed with switch intact, deep joy! but it all seems clean and new looking inside and now with cleaned contacts but the result of this session has made no improvement sadly, still only getting action on power setting 6.

 

[Seath]

Not having much experience with welder transformers, would one be able to find out the expected resistances on each wired connection to enable testing for failures / breakages on the transformer?

 

[eddie49]

The primary resistance of the main transformer will be between one and two ohms. That is across the whole winding. From the start to each of the six power taps, and between the taps, there will not be any measurable difference - but there should always be continuity.
With most typical digital meters having a lowest Ohms range of zero to 200 Ohms, it will not be easy to come to a precise conclusion, but you can at least make sure that nothing is open-circuit.

 

[Seath]

 

[Seath]

I finally got round to testing the main transformer. I am not sure If I have covered all the bases? All the blanks are open circuit.
Thanks in advance for any info. Duncan

 

[eddie49]

I like the look of your fancy Megger Ohmmeter! The one I have is red bakelite and it has a crank handle...
Those are interesting results but I'm not sure that I understand them, 0.02 Ohms is too low.

In an earlier thread, I measured the transformer primary resistance on my 200A MIG:
https://www.mig-welding.co.uk/forum/threads/sealey-180-supermig-v3.88076/#post-1278482

I was going to post this info earlier, it may help:

Assuming that the mains input is 240v AC and the welding voltage at the highest setting is 24v, then the required step-down ratio is one-tenth.
To get a turns ratio of 10 to 1, if the secondary has 100 turns of thick wire, then the "main" part of the primary would have to have 1000 turns of thin wire.
From the start of the winding to the first tapping, I would expect the primary resistance to be less than 1 Ohm - maybe 0.2 or 0.3 Ohms, but not zero.
This first tapping after the start corresponds to Position 6 of your power range switch - the highest setting.
To get a lower voltage out of the secondary, you actually need more turns on the primary.
If the lowest welding voltage is 12v, the turns ratio needed would be one-twentieth. So from Position 6 down to Position 1 there would have to be 1000 more turns on the primary, with 5 tappings at 200-turn intervals.

On your MIG, Position 6 works, the rest don't. This implies that the first 1000 turns ( or whatever ) of the transformer primary is OK, and the wire emerging at the first tap and going to the power switch is OK. The problem is that the wire which loops back in to the rest of the winding, and the other 5 taps, is broken.
This earlier thread about the same model mentions similar issues:
https://www.mig-welding.co.uk/forum/threads/lincoln-185-compact-mis-behaving.52242/

From the start of the primary to the wire that leads in to the switch screw terminal for Position 6, continuity must be OK. From the paired wire that leads back in to the transformer from switch position 6 to all the other five tappings, there must be an open circuit. I would suggest stripping back the insulation on that Position 6 pair, and checking for a broken wire.

 

[Seath]

A sparky by trade requires a decent Multi function tester!
Thanks for the great info.
The chart is read while having in mind I tested the transformer wire 1 against transformer wire 2 then 1 to 3 then 1 to 4 and so on so on. The meggar MFT is set to low ohms and it measure .02 ohms between
1 and
2 and 4
3 and 5
4 and 6
5 and 7
6 and 8
7 and 9
8 and 10
9 and 11

I will try and understand how the transformer is wound from your information, without having such a luxury as a diagram correlating wire numbers to transformer windings, in order to identify which wires correspond to power setting 6. I imagine I will just need to get stuck in and expose the wires from the insulation and see what I can discover.

Many thanks

 

[eddie49]

The wire at the start of the winding will be just a single wire, in the sticky woven sleeving.
All the tappings will have two wires inside the sleeve, apart from the last one, which will again be just a single wire. This last one corresponds to switch position 1, the lowest power setting - and the highest resistance from the start of the winding - maybe 1 Ohm ( if there is no break in continuity anywhere ).
I did think that the tapping points were loops, with the wire emerging, cleaned from enamel insulation, then going back up the sleeving. However, the wire is actually cut, and relies on the screw terminals at the power range switch to form the loop.

 

[Seath]

Ok second round of tests and I feel we are getting somewhere now. I joined the ends of the looped cables as seen in photo.
I continuity tested between the single wire 1 and each of the looped wires then repeated this with single wire 2.
Open circuit between wires 1 and 2 ie the whole winding if I have understood correctly and no continuity between loop 12 and either single wire. Could loop 12 the culprit?

 

[Seath]