Snap on pro mig 187 low on power ?

[eddie49]

Did you try the 3 x car headlamp bulb load test?
I'm beginning to suspect that the transformer primary isn't getting full power in. You'd need to trace where the AC mains goes into the primary when the mains is on, the trigger is pressed, and the power selector switch is at the highest setting. Then disconnect those wires and rig up a direct 13-amp fused new mains lead direct in to the transformer at those points.

 

[anto44]

Check the voltage selection switch, I had a similar problem with my snap on promig and it was the contacts in the switch had burnt out. I think I still have the old switch at home I'll get some pics if I do. There was a big voltage drop across the switch.

 

[johnny]

Ive had a look at the power setting switch...i cant see any burnt connections..
I measured the ac from the transformer..it was 24 volts..
Im sure it was 26 the last time i measured it..?
Not tried the bulb test yet eddie...

 

[johnny]

Ive inboxed u eddie

 

[anto44]

My switch looked perfect from the outside it was only when I did a voltage drop test across it I found it was faulty and only supplying about 150-160 volts to the transformer.

 

[johnny]

Really...can you still buy the switches..?

 

[Jon Andriotis]

I understand that this is an old post. First off I must say that I am no electronics wiz, I probably know just enough to be dangerous. I have a Snap-On MB135 that seems to be having a similar issue. At first it would not feed any wire and I found a burned trace on the PCB with the feed controller on it from the Line in to the relay. I repaired that with a piece of wire. Voila! the wire started to feed again. Problem is it was welding like crap. After much research, figuring, and head scratching I came to realize that the feed rate is very low (about 230 inches per minute MAX). THe wire spool had rust on it so I cleaned the liner and spryed everything own with WD-40. Everything started moving smoothly and the speed increased greatly (I havent measured it yet). Problem is when pull the trigger and freewheel it, it moves right out, but then I tried to strike an arc and it bogs right down. I thought it was in the controller PCB but after reading your posts I am wondering about the voltage switch. I was curious if Johnny ever figure his issue out. I am also wondering If anyone has a schematic for the wire speed controller PCB for an MB135. Im Not sure but I believe that the MIG135 is going to be the same or very similar. Thanks for any input.

 

[paulo1974]

Any luck jon?
For the info plate of the welder the 187 amp machine has even worse duty cycle than my 140 amp mine on paper has 20% at 135 amps and 60% at 78 amps. And mine welder welds like crap or maybe the welder .
I will try what eddies49 says on my case a 2 12v car light bulb . As my welder has change polarity i will connect the light to the + and - dinse and press the trigger on the torch. I already connect the gas 24vdc valve to the dinse when i retrofit the welder from fixed torch to eurotorch.

 

[sol-car]

Good afternoon
I'm a new member, and I bought a second-hand snap on mig pro 187. but it has the same problem. little power
I suspect it's the 6 position switch.
Where can I buy one. thank you very much

 

[eddie49]

Hello and welcome to the Forum.
Have you tried the checks mentioned in Post #5?
If so, what DC voltages do you see at each of the six positions?
I guess that the 6-way switch is just 1-pole, 6-way. Does the rotary action feel damaged or notchy?
When welding the appropriate thickness of metal, do you consider the power to be too low at every one of the voltage positions?
If you can identify the terminals for the "pole" and the six "ways" at the switch, you could use an Ohmmeter to check the internal resistance. It should be about zero Ohms in every position.
If you are sure of the wiring layout at the switch, you could select one "failing" position and then bypass the switch by jumpering directly to the transformer tapping. If there is no improvement, then it is not the switch.
In my experience of the welder involved in this thread, this particular model of Snap-on welder is just not very good.

 

[Nix2]

I think that in this case it is not 1-pole, I think that Snap-On(Cebora) used characteristic connectors, as in the diagram for Cebora ART 838.
This can be easily used, even without a solution, because if it is connected as per diagram, 5 contacts and characteristic jumpers-bridges are used, one double jumper (2 terminals), the second triple jumper (3 terminals).

If 1 pole occurs, a larger jumper will occur (6 terminals).

Of course, as Eddie49 writes, you can also measure with an ohmmeter.

@sol-car - if it is first determined what the switch's connection layout should be, I will propose a new switch (matching replacement) Polish production, I have several types.

 

[sol-car]

Good morning
I carried out the tests without and with 55 W car bulbs.
The voltages I obtained results from are as follows.


I managed to weld but with little power. thicker iron.
I removed the selector and directly connected the input wires to the output wires to position 6 for maximum power. And in the first test, it seems to be better.
I used the test from, eddie49. Congratulations to him too, https://www.mig-welding.co.uk/forum/threads/snap-on-pro-mig-187-low-on-power.95599/post-1429362

 

[sol-car]

This was the schematic I got. and I present the old selector.
the 'R' are the inputs and the numbers are the outputs

 

[Nix2]

Your connection diagram contains errors, they are probably the result of testing the "transition" with an ohmmeter...

To ensure reliable measurement results, it is worth testing the "transition" with a 40-100W/230V bulb because then the switch contacts work in optimal conditions and the transition measurements are reliable.

BTW, this is the connection system and diagram that I provided

 

[sol-car]

thanks.
I've been reviewing the switch connections.
and it appears to be correct.
How I bought the machine second hand. They may have connected something in the wrong place. All that’s left to do is make the right connections. I did a test with another machine, at maximum power. and here is the result

 

[sol-car]

As you can see in the photo, S3, S7 and S5 have 2 wires. They go to the switch output, transformer input
corrector 1 and 3, his 'R', ; 5, 7, and 9 ins 'S'

 

[Nix2]

Yes, now the diagram is correct (and consistent with the Cebora electrical diagram)

 

[sol-car]

Thanks Nix2.
Is there any way for me to connect the wires to the switch. If I hadn't taken the numbers.
thanks again.
I think wire 1 and wire 9 should be at the ends?

 

[Nix2]

Yes, exactly like that (and according to the Cebora wiring diagram). Single wires are the beginning and end of the winding.

 

[sol-car]

Sim, exactamente assim (e de acordo com o esquema eléctrico da Cebora). Os fios simples são o início e o fim do enrolamento. você