SIP Handymig Wire Feed Stopped Working

[thomp1983]

Hi All,

The last time I used my SIP handymig the wire feed stopped working, as I needed to finish the job I was doing I went and bought a different welder and this has sat in the corner of my garage waiting for me to do something with it.

I've stripped the cases off it to have a look, when the torch trigger is pressed the relay on the pcb clicks as I'd expect, I also used a 12v power probe to supply power direct to the wire feed motor and it works so the issue is the supply to the motor.

above is a picture of the pcb, all the joints on the back look in good condition and as I said the white relay in the top left corner clicks when the triger is pressed. I'm guessing the black tansformer in the centre of the pcb has failed but thought I'd check in here?

The label on the transformer seems to suggest it's 230v in and 12v out unit but every other post I've found online for sip units suggests the wire feed motor is a 24v unit?

I've also found some other posts about fitting a dedicated power supply to run the wire feed motor, If I was to do this would I still need to replace the transformer on the pcb or would the new power supply bypass this?

Thanks
Chris

 

[Domdom]

That board should be easy enough to troubleshoot if you have a meter
Just because the relay clicks down't mean the contacts for the high current side are OK, they could well be burnt out.
That's a 12v secondary transformer with a rating of 1VA so shouldn't be hard to source.
The thing to do is go through it logically with a multimeter. Probe the 240v side of the transformer - is it getting power? Probe the live side of that relay - is that getting power? Then probe the switched side and operate teh relay, does the power flow through ok? And so on.
The discreet components look fine, those would go black if burnt out. Maybe put the meter across the potentiometer and check that the track is OK and that the resistance varies between the wiper and one end when you turn the knob. Middle contact would be the wiper so probe middle and either of the other 2 on resistance scale of 10k. It's a 2k2 pot so the outer 2 contacts should show a resistance of 2200 ohms ish.
Not sure about that device (DIAC or FET maybe) bolted to the heatsink though. That possibly looks as if the legs may have got hot at some point. Could be the light though.

 

[thomp1983]

Hi Dom,

the potentiometer works fine I checked it before I made the post, I've ordered another transformer anyway as there cheap enough. I'll check the relay fully and take a closer look at the bit mounted to the heatsink when I get 5 minutes

Thanks
Chris

 

[eddie49]

The only purpose of the small transformer on that PCB is to drive the relay coil. Since the relay does operate, the transformer must be OK.
Power for the wirefeed motor comes from the main welding circuit, via the speed control components on that PCB. The next step is to check if the main welding power is on after the relay closes. Although the wirefeed motor does not turn, can you still get an arc from the wire tip?

 

[Alan Reynolds]

Just a thought here. Try all the cdurrent switches on the front for being halfway between positions or are faulty. You can easily check them in each position with a meter with the machine off. I've had a couple of SIP's with no feed and this was the problem.

 

[thomp1983]

Top marks to Alan, wiggling the current switches back and forth has brought it back to life, next I'm going to look into stripping and cleaning all the connections as everything does look a bit nasty in there, I'm also going to look into replacing the wire feed pot as the one fitted isn't supposed to be very good

Thanks for all the help

Chris

 

[angellonewolf]

there only rocker switchs just change them ?

 

[Country Joe]

there only rocker switchs just change them ?

Probably wouldn't help much - as the switches on the front tend to do this anyway, from time to time.
I had one quite a while back, and it suffered with the same symptoms if the switches were full of crud.

All the Best,
CJ