Clarke AT131 resistor

[marinaman]

Hi. I have an inverter with some burned caps and a resistor. I have rang Clarke,
they do not sell components. Only the main board which is more than a new
machine.
Does anyone have a wireing diagram or another welder they can read the values? Just the colours off the resistor would be fine.
Thanks, Jerry.

 

[PTvor]

No, but I doubt changing that resistor and the caps which appear burned would do much good. There may be a host of parts which have been damaged but where the damage is not so obvious.

It looks as if something else has failed which has put a serious over voltage on a part of the circuit which runs at about 12-15V. I suspect it's the circuit which converts the DC on the main capacitor bank (probably 330V) to low voltage for the control electronics.

You really need the circuit diagram to tackle this, and you'd need to find and correct the root cause first. Even then you may be basically rebuilding the inverter.

 

[marinaman]

Ta Ptvor. I take it you suspect this thing is scrap. I'll take it as an opertunity to learn.
What are my chances of finding a diagram?

 

[PTvor]

Not at all. I think it looks like a challenging project and useful learning experience

I'll send you a PM.

 

[marinaman]

Clarke inverter

Thanks again. I am struggling through the info.
I'll test the volts to the control circuit.
When I get that right I'll have a go at the caps and resistor.
I'll only zap myself a couple of times. I need a better multimeter.
Clarkes are very popular and many peoples entry to welding like me,
but I am meeting a chorus of they're crap.

 

[PTvor]

Best of luck with it.

I'd start with checking that the voltage on the main capacitors was what it should be and remember that you don't necessarily need to have the machine connected to the mains to do that, you could use a bench power supply.

You can also power the control electronics and fan from a bench power supply and check that waveform getting through to the gates of the IGBTs looks right.

I found the cct diagram for my inverter by finding on the WWW a picture of the cct board which looked the same and chasing it up.

I've got two inverters the same and fortunately the faults were fairly simple, not loads of damaged components.

Clarkes are very popular and many peoples entry to welding like me,
but I am meeting a chorus of they're crap.

Not really.

My impression of Clarke on here is that the MIG machines are regarded as about as good as you can get for the money and worth having. People have doubts about the newer ones.

Their buzz boxes are just buzz boxes and no one much compares notes about the best buzz box these days.

Their plasma cutters aren't mentioned much.

They don't do proper TIG machines as far as I know.

Their MMA inverters don't get much of a mention either as a good buy or rubbish. Probably the cheap inverters talked about are RTech, Thermal Arc, Tech Arc and Parweld, and for serious money, IFL, Lorch, EWM and that sort of stuff.

The rubbish is the phenomenal bargains from ebay, some of which don't work out of the box and which can involve you in all sorts of hassles if they go wrong.

I must say that if I was looking for an inverter for about £200, I wouldn't be looking at Clarke. I don't think they managed to establish their name with inverters the way they did with MIG machines.

Second hand Clarke inverters seem to fetch a tidy price on ebay.