syncrowave stopped welding - any hints?

Can't see any pic, Mark?

Al.

Hmmm... it's showing for me, and it's hosted on here. I'll try attaching it...

Please excuse it's undressed state - I have been probing inside extensivly...

Did not find any info on that serial number but have emailed you a manual that should help.

Cheers

Thanks for your efforts Jake. The manual suggests a couple of other places to check that I have yet to try, so I see if I can get anywhere with it tonight.

Thanks
Mark

Couple of things you can check :- there is a switch for MMA/Stick, it is the
"Contactor local/remote" switch, top left, local is mma, remote is triggered by
the torch switch, turn HF off and put into local, check for OCV, 70 volts ish.

Try moving the "Polarity Straight/Reverse" and "Range High/Low" switches up and down a few times, the blades on those switches can get dirty and give a bad contact.

There is no Contactor in that machine as such, the main pcb fires the Thyristors to get OCV when it recieves on signal from switch in Local or trigger pressed, this signal goes into an Optocoupler which in turn starts firing pulses to the Thyristors. Very common for that Optocoupler to fail. Shows as HF on, Gas on but no OCV.

smp, that sounds like exactly the problem.

Tested as you mention - set to local, and HF turned off, the OCV is 0V.

Switched have been moved around, and in some cases the terminals/wipers have been cleaned up with little light emery cloth action... still nothing.

It sounds a lot like either the Optocoupler has failed, as you suggest, or the Thyristors are not being fired.

Could I be really cheeky, and ask you to let me know where the optocouplers are on the circuit diagram I posted earlier... and is there a way to bench test them?

Thanks very much for your help.
Mark