Clarke 151te sudden spark loss

[Tony_C]

Hi folks,

Im hoping someone with some welder knowlege can help me get back on track as my electrical knowlege is not extensive. I fired up the welder to do some tac welds on an exhaust downpipe. I got an initial spark then it suddenly died. Welder has been working great over the past couple of months.

The wire feed and fan still work. I have checked each diode on the rectifier and get a reading of 0.4 on each so I assume they are good. Between low-high power settings I get ~28-35 VDC between the torch tip and earth with trigger pulled. On the output of the transformer I get 30 VAC with trigger pulled. I dont see any burned connections and the relay makes contact with the trigger pulled.

When I first opened the case I noticed the ground cable which goes from the transformer to the casing ground had been pinched and severed. I have since replaced the cable.

Any suggestions on what else to check would be appreciated.

Thanks

 

[a111r]

That's a good start.
Check out the 'earth' return crimped joint to the inductor, they go bad and are hidden under braid. This thread shows it:

Another deal Clarke.... I'm perplexed!

Fixing up yet another neglected Clarke 90 tonight, I'm now rather perplexed. In my limited experience, if the measured open circuit voltage over the power range is spot on (as in this case: 19 vdc to 28 vdc over the 4 settings ) and the wire feed works (which means a good PCB), then that is...

www.mig-welding.co.uk

The OCVs you've measured are a bit high, they should be nearer to the range of 18vdc to 30 vdc.
I would clean up the voltage selection rocker switches and measure them again.

 

[gaz1]

there simple on those

main things to check

check switch hasnt gone faulty
check diodes
check transformer windings

 

[Tony_C]

Thanks guys. I pulled out most terminals and did some further checks. All looked good. Then I checked that crimp on the earth - inductor cable. It looked not too bad but I gave it a clean up anyway. Now I have spark! Many thanks for that suggestion a111r, I'll give it a proper test in anger tomorrow. May as well order a new crimp and redo it.

Cheers

 

[a111r]

Good stuff.
A big 30 Amp screw terminal block works well for re-making that connection.