I have a SIP 150 was welding lovely and all of a sudden there was a loud pop and now even at maximum power it hardly melts the wire, let alone any penetration.
Any ideas what’s gone wrong? Taken the sides off and can’t see anything obvious?
Hi and welcome. Great bunch of guys on here and no doubt someone clever will be along shortly but meantime there's me!
The Sips are pretty simple machines and there isn't a lot there to go pop but one of the things that can do is the rectifier diodes. These change the alternating current from the main transformer to direct current for welding and have to pass an awful lot of power when you're welding.
I believe on your Sip there are two of them and you'll find them mounted on large flat aluminium plate/s near the big transformer. You should be able to easily recognise them.
You really need a meter to trace and test the innards of the welder and a simple cheap one is fine and doesn't cost more than a few pounds.
If you've got or can borrow one you can set it to measure the diode function which allows current to pass in only one direction and not the other. If you try the two probes one at each end of each diode and then swap the probes and try the other direction you should see completely different readings in each different direction. You may well find one of them measures the same in both directions which shows it's probably faulty. This is with the power off and welder unplugged.
The only caveat to this is that the diodes are connected together through the transformer so the readings may be very similar and not obviously different enough to be certain. To be more certain you need to disconnect one end of each diode to take them out of circuit. One connection is to the plates/s they are mounted on and this may be the most convenient to disconnect from the circuit.
If the above makes no sense then please wait and someone else will be along shortly no doubt.
Another easy test:
Remove the gas shroud (checking that spatter hasn't shorted it to the tip..) and set your meter to DC to measure the welding voltages between contact tip (+) and earth clamp (-), when triggered, over the 6 settings.
Should be a range of c. 18 v to 32 v. Any anomaly here could point to a failed transformer winding, if the push button switches are all OK.
There you see I told you the guys would be along soon
Even an offer of spares to help you out. Can't get much better than that.
Don't know if you've spent any time looking through previous posts on here but just about every fault has been discussed and worked through before and all the information is here. It means a lot of reading but you'll pick up so much knowledge it's worth the time.
Meanwhile just follow the suggestions and you'll soon be up and running.
Ok so picked up the welder and have it at mine. So one minute it welds fine, and doing what a111r suggests I’m getting 37v on high. Then it won’t weld and barely penetrates and still on high it’s low 20v’s.
Also confusion between myself and Dad, there was no pop. It just suddenly started doing this.
I’ll do some more investigating when I have more time.
Sounds like you are losing 15v or more across a high resistance in the welding current path - i.e. a corroded or loose connection. Try welding for a while, then switch off & unplug and check for hot-spots on all connections in the secondary path.
Ok so had a quick look this evening, and saw a lead which was coming from the wire motor to a 10mm bolt connection. This looked poor, so reterminated and cleaned up the connection as very rusty. Just done about 20 mins welding no problem? But I wouldn’t think this would effect voltage? Just stop the wire from turning?
Hope this makes sense?
Good work!
That terminal is the DC +ve voltage supply from the rectifier to the torch.
And yes, the welding voltage also powers the motor... I will leave it there!
Thanks for your help guys! I’ll see how I get on. Reckon I’ll stick around, as my welding skills have a lot to be desired! I might learn something here! Dads the welder.... but he isn’t good with electrics!