SWP 211 advice needed!

[julianthegypsy]

Hope this is in the right place. I have a swp211 that I picked up off evilbay allegedly in working condition...well it lights up but pull the trigger and nothing happens. Pulled the euro connector off and one of the pins was jammed. Result! Freed it up, pulled the trigger and ...nothing. Took the side off and discovered two wires that had been rubbed bare on the edgeof the transformer and obviously shorting. Go me! Taped them up and routed them clear of the transformer. Switched on again, pulled trigger and...nothing. Another look around and realised that one of the diodes on the rectifier is blown, as in the solid wire has burnt like a piece of fuse wire.
Now. Steve at weldequip was most helpful and has quoted me £60 for a new rectifier which seems reasonable, but my question is, what would cause it to blow in the first place?
The unit actually looks in nice clean condition but its going to take a fair bit of work as well as the sixty quid to fit the rectifier and I'm loathe to shell out then find it still doesn't work or blows up again ten minutes later. All advice gratefully received!

 

[Lawnmowerboy]

Diodes do break down from time to time. Often because of overheating. Happened in my little Clarke.

 

[julianthegypsy]

Diodes do break down from time to time. Often because of overheating. Happened in my little Clarke.

Thanks. I assume that would result in all the lights on but nobody home?

 

[Lawnmowerboy]

Well it's pretty much the last step if you like before the welding current is ready to leave the welder apart from possibly smoothing caps. It should still feed wire so check the continuity of the switches and the operation of the relay. The tranny for the wire feed PCB may be dead and check the potentiometer and see if it's open circuit.

 

[the repair man]

Do you have the part code for the rectifier? I paid a tenner for the last one I ordered, I can check my suppliers for you.

 

[julianthegypsy]

There's a load of numbers on the rectifier, which are:
PMS 8/4/1
22400101
10/2009
If that helps.
How do I check the potentiometer and the wire feed transformer? I assume I should have continuity on both sides of the trans, if I can find it, what should I see at the pot?
This is of course in idiot terms, me being an idiot in these matters!

 

[mike 109444]

No mention as to weather the contactor was operating, was it?

 

[the snooper]

you need to check if there is any ac power to the rectifier, most rectifiers short out when gone and cause the welder to buzz badly as it shorts the transformer

 

[julianthegypsy]

No mention as to weather the contactor was operating, was it?

Nothing happens at all. Turn it on and the light and fan comes on as far as I remember but apart from that its dead. Squeeze the trigger and there is no sound of contactors or feed motor.

 

[the repair man]

Hmm, sounds like you need to give it to someone that has a better idea how to test it.
If a diode has gone on the rec, simply replace the diode. You say nothing is switching, have you checked the switch in the torch is actually working? after that it is a process of elimination. Continuity through a transformer wont help you. You need to check the primary is getting 240v and the secondary is giving out ( whatever your welder is listed at ) prob 20 to 50 vac. Is your contactor working? put 240v to the coil to test, or switch it manually and see what happens. There is normally a part in the centre or end that can be slid/pressed in. Your wire feed wont work until you replace diode as it is dc, probably 24v. You should be able to get a diode really cheap. If your unsure, please be careful, electricity can be a sneaky turd.
The light and fan are 240v, so will work despite the rectifier. It also suggests you will be getting voltage to the primary.

 

[mike 109444]

Pretty much as TRM has said.
Were the wires rubbing on the transformer from the transformer?
Is there a smaller transformer (bout 4 or 6 inches square). If so this will supply the lower voltage to the pcb, about 30vAC if this is duff then there is no voltage for the pcb to operate items such as the feed motor, gas valve and contactor.
Pics of inside will help point you to what to check.
There are plenty of bits to check before you splash the cash.

 

[Lawnmowerboy]

Could be as simple as the switch in the torch is fubared.