Welder troubles again

[landrover598]

Yet more problems with my SIP/Cosmo 145 This time the wire feed is constantly stuck on, even if i disconnect the trigger wire which comes from the torch.

Any suggestions as to where to look to fix the problem, I've had a quick nose around insdide the machine, and can't see any shorting wires or burnt out components.

This welder has survived a few vehicle builds but perhaps it's had it's day now ?

[T1G UP]

the wire feed is controlled from the triger on the torch so try tracing that back

[Retroanaconda]

Is there a control board for the motor?

If so, does it have any large transistors on it? Or a 555 timer IC chip (used for PWM)?

I just fixed a similar issue with mine, the wire speed was permanently at full whack irrespective of setting, I solved it by replacing the output transistor which had shorted internally

[Disco-Ron]

You could have a short between the two wires in the lead up to the trigger, see if you can disconnect the cables that go into the wander cable, and see if the cable feed stops.......... if it does, you need to re-wire it...............

[landrover598]

You could have a short between the two wires in the lead up to the trigger, see if you can disconnect the cables that go into the wander cable, and see if the cable feed stops.......... if it does, you need to re-wire it...............

Thats what i thought but like i said in my original post, i've tried this

This time the wire feed is constantly stuck on, even if i disconnect the trigger wire which comes from the torch

There is a circuit board in there, but i've got no idea what any of the bits on there are

Time for a grown up to look at it i think

[Retroanaconda]

Give us a photo of the circuit board if you can?

Also worth putting up a thread on http://www.mig-welding.co.uk

That's what I did, and the knowledgeable chaps on there diagnosed my issue quite quickly once I had done a few quick tests.

Here's my thread on there:

http://www.mig-welding.co.uk/forum/showthread.php?t=19334

[landrover598]

Give us a photo of the circuit board if you can?

[Retroanaconda]

The output transistor is most likely that one that's bolted to the large aluminium heat sink there. If you're handy with a voltmeter you can test it, and most of the other components.

I'm only going by my own experience here, but I think it is likely that something has shorted on that circuit board. A simple test to determine where the fault might lie:

1. Turn the welder on, so it starts feeding wire (uncontrollably)

2. Turn the wire speed knob.

Does it adjust the speed?

If the speed adjusts, then it is likely that the on-of control side of the circuit has suffered a problem. If it doesn't adjust, and just keeps going full-speed, then it's the speed control side of the circuit. Or both

[landrover598]

1. Turn the welder on, so it starts feeding wire (uncontrollably)

2. Turn the wire speed knob.

Does it adjust the speed?

It does, yes.

I'll dig out the multimeter and have a poke around.

[Retroanaconda]

There's what looks like it might be a relay on the board, bottom right in your pictures. The light blue semi-transparent thing. I would have *thought* this would have been used to switch the output, although this is where a more in-depth knowledge of the system comes into question.

If it is indeed a relay, see if it has shorted across either the coil contacts or the output ones. It should click when activated, and click again when deactivated.

[landrover598]

a relay on the board, bottom right in your pictures. The light blue semi-transparent thing

Your diagnosis what right, it looks like that relay had stuck, i gave it a quick thump and seems to be working again Cheers