Snap on pro mig 2000 blowing fuses....

[willt1988]

Hi everyone, im in need of some assistance. I have a snap on pro mig 2000 which i believe is base on a cebora machine, which is blowing fuses. If i hold the trigger down to feed the wire through then it will quite happily run for as long as is needed, however once i start welding, within two seconds, so maybe two trigger pulls it blows the trip. I bought the welder used and voltage settings 3 and 4 didnt work, i traced this to a burnt out voltage selector switch, which i replaced. All the settings work now, but i wonder if the switch being burnt out is cause or symptom of the overall problem, i dont know if it has maybe back fed and affected something else...rectifier maybe?

Any thoughts greatly appreciated :-)

 

[mike 109444]

Welcome to the forum Willt1988.
Does the welder trip if on the lowest setting (1?).
Are you confident that the replacement power selector switch has been wired up correctly (same as ori).
Was the welder working before (less the 3 and 4 positions)
The wire feed power will come from a seperate transformer so would not be affected by a fault in the main transformer, power selector switch, rectifier, capacitor, or inductor.

 

[willt1988]

Thank you mike 109444!!!
I need to check if it blows on lowest setting, will do that this weekend. I'm quite confident that it was wired up the same as i marked each wire position on the switch and the wires and took pictures, so i would hope i didnt get it wrong. The welder did work before, although i cant remember if it blew fuses or not, i was too indulged in working out why settings 3 and 4 werent working. So i think we can assume that the wire feed side of things is okay... someone has mentioned to me about checking diodes and things???? is there any way of checking rectifier, capacitor and inductor for say high resistance or anything? i have a multimeter if needs be. Many thanks

 

[mike 109444]

Does your meter have a diode test option?. Will have a diode symbol somewhere round the dial. This would still only give a basic test of a "high power" diode but will show if it is dead short (that is possible to test with the resistance part of your meter. Headach is you will have to isolate the diodes from part of the circuit. You are probably looking for a short more so than a high resistance. The diodes will be mounted on a large ally plate and will be bolt through type?. Got a pic of inside m/c or maybe a circuit diagram?

 

[willt1988]

hi again, i didnt have a chance to test on setting number one. I did however manage to do a quick diode test. I found two small components that i think look like diodes, one is bolted on between the earth lead socket and the welder casing and one is bolted between two large cables somewhere in the middle of the welder. As you say the diode test is just a simple continuity check, and i found the one in the middle of the welder to be okay, but the one between the earth lead socket and the casing is open circuit as far as i can work out. there is nothing on the continuity reading, so i checked resistance on various settings, and nothing... so im guessing its open circuit.

 

[Robotstar5]

I found two small components that i think look like diodes, one is bolted on between the earth lead socket and the welder casing and one is bolted between two large cables somewhere in the middle of the welder.

From their locations, they sound more like capacitors not diodes.

 

[willt1988]

I think its time to get it properly diagnosed. Does anyone know of a machine repairer in the south east? near buckinghamshire. if not then i might try a company called r-tech welding... anyone had previous experience?

 

[willt1988]

Hi all, thanks for your help so far. i have tried the weler on settings one and two this morning and it works a treat!! i think in all my enthusiasm trying it on settings 3 and 4 which were faulty before, i didnt try the lower settings, which by the looks of things i will be using more anyway. I think the fault with the switch burning out and the thing blowing fuses is definately linked. so i think the fault lies somewhere in either transformer or rectifier...but i can get that fixed at a later date now and get on with what i actually bought the welder for...project girlfriends beetle :-)
Thanks for your help guys

 

[Wozzaaah]

Unless I've missed it you've not been asked what supply you're feeding this welder with.
It could simply be that it's drawing more than you're supplying which is why the lower settings work but the higher ones don't.
What size and what rating MCB are you running it from?

 

[willt1988]

Well this has been something that i have thought about. Im using this welder at home and have had the electrics upgraded to suit as the house is old and so is the wiring. So i had an electrician come and fit a seperate breaker box run direct from mains supply, with a large waterproof 3 pin round socket and then heavy duty cable from the mig with matching plug. The breaker box is currently running a 32amp trip which is the one that goes every time, but it says on the front of my machine max current 24 amp. the trip fuse is upgradeable to 60 amp the guy said. Do you think its worth a try? And excuse my ignorance...whats an MCB?? Thanks

 

[Wozzaaah]

MCB - miniature circuit breaker ('trip')
At 32A you're already well over what the machine should draw so don't put a bigger one in as it's not necessary and also not safe.
Unless the MCB is faulty it does sound like the machine itself is at fault.
Just as a test, do you have another 32A MCB you can swap for the one that trips? It would at least eliminate that from the equation.

 

[Robotstar5]

Does it have B32 on the mcb? if so it may be worth changing for a C32 which will take the initial current longer than B32 before tripping.

 

[willt1988]

ah i see, that makes sense!! thats what i thought when i saw that it said 24 amp max on front of the machine. i upgraded the electrics because the welder was blowing the downstairs trip before, and i thought that it was just because the trip wasnt 'man' enough for the job. So had it all upgraded with brand new stuff and it still blows on settings 3 upwards (havent tried 5 and 6) so im sure its a machine fault, especially considering the switch was burnt out on 3 and 4.

It currently has a B32 so C32 might be worth a shot... whats the difference between the two?

 

[Robotstar5]

It currently has a B32 so C32 might be worth a shot... whats the difference between the two?

A "C" type will handle twice as much initial current as a "B" type.

 

[willt1988]

Ah cool thanks for that.

 

[Steven burke]

Did you ever find out what caused the problem because I have the same welder with the same issue

 

[eddie49]

The welder is tripping the input breaker when switched to higher power settings? What size breaker are you running on, have you tried other power sockets on different mains circuits? Does the machine weld correctly at low power settings?
The fault could be a shorted diode in the rectifier. These can be tested with a meter, and if defective, can be replaced ( maybe with a similar but equivalent component.)

 

[Steven burke]

The welder is tripping the input breaker when switched to higher power settings? What size breaker are you running on, have you tried other power sockets on different mains circuits? Does the machine weld correctly at low power settings?
The fault could be a shorted diode in the rectifier. These can be tested with a meter, and if defective, can be replaced ( maybe with a similar but equivalent component.)

I have tried it in work it does weld up to setting 3 and after that trips the board I work in a garage that runs lifts and we also have 3 phase so we must have high output trip boards it will trip on 4 and 5 after a couple of pulls of the trigger

 

[eddie49]

When a MIG is switched to higher power settings, the range switch is actually connecting the AC mains voltage to less wire in the transformer primary winding. So it is not very likely to be a fault in the transformer. The range switch itself could be faulty - they can short out and burn internally. Does the switch rotate freely and smoothly to each position?
It's possible that some component is breaking down at the higher voltages that are used for the higher power settings. However, most MIGs start about 16v on the lowest setting and rise to only about 33v, so that isn't much of a change. The component could be the rectifier, or the capacitor ( if this machine has one ). For the latter, you could test with one lead that goes to the capacitor(s) disconnected and insulated. A MIG will still weld without a capacitor; check if the breaker still trips.
To get an idea of the output voltage range, you could shut the gas off, release the wire pressure roller, then measure the DC volts between the torch tip ( positive ) and the work return clamp. Going up through each position of the power range switch, from 1 upwards, the tip voltage should rise steadily from about 16v towards 30 or 35v, before the machine trips out.

Another test would be to unplug the machine, set the main power switch on the front panel to on, and measure the input resistance of the transformer primary for each position of the power range switch. To do this, you would need to manually engage whatever contact device is used to turn the transformer on. That could be a Contactor, with a "manual on" button on the top. At the lowest setting of the power range switch, the transformer primary resistance may be about 2 Ohms. Stepping up the power range, that will fall to maybe 1 Ohm or less, but it should never be zero. A typical digital meter may only show 0 to 200 Ohms on the lowest resistance range, so this value may be difficult to check.