I'm getting a new welder soon but in the meantime there's a strange problem with my old one..... Any ideas?

I tried welding some 25*1.5mm box together and I'm getting hardly any penetration I attacked the box section with a breaker bar and most of the welds just broke at the weld- 1 weld broke at the surrounding metal....

It's a Clarke90 turned up to the max power-wise and I'm running it right off the socket (no extension lead anymore) but it's just not doing it's thing!! The wire speeds spot on and it's laying a nice bead but it's stuck on the surface rather than penetrating.... I'm using 100% CO2 (which is supposed to help!!!)

Surely even a puny C90 would penetrate through 1.5mm of m/steel? When I cut through the section I'm getting 0 penetration..... It's an old unit- do the transfomers get knackered eventually?

If I weld a lot in the same area eventually it starts glowing a bit and I get some penetration (especially near the edge of the box section)...

Bizarre? Any obvious checks?

TIA!

Has it been used with gasless wire ?
If it has, has someone switched the torch neg/pos back afterwards ?

check the earth clamp for corrosion or rust. I clean mine with some sand paper, also check the clamps on the machine. Mind that although the current flowing through the wire is very high the voltage is very low so resistance of bad connections can have quite a detrimental effect on the weld. Also keep the earth clamp as close as you can to the weld rather than at the other end of the car for the same reasons. Winter is a common time for this to show. One sure sign is that an electrical connection is getting hot during welding and it will only get worse over time.

[Edited on 5/1/09 by Mr Whippy]

No it's never been gassless.

Earth clamp could be a candidate for a quick check- it looks a bit ropey, could be giving some resistance.... Good plan...

any highish resistance, and it is probably not notcieable on a DVM - will certainly show itself as a hot spot once the amps have gone through it.

Yes, I did notice the earth clamp was quite hot today and where it's crimped onto the wire the insulation had melted Excellent!!!

Hi, try using argon instead of co2. It gives a cleaner stronger weld.

quote:

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Originally posted by vyperstrype
Hi, try using argon instead of co2. It gives a cleaner stronger weld.

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Yup. Tried CO2 with a hint of argon. Neat welds but even worse penetration