I'd have to agree with the majority - the former owner has already
tried swapping boards, so odds are it's not a board. Bad power SCR or
Triac in the output sections, bad potentiometer or cabling in the
controls, bad safety switch, open coupling capacitor, bad
opto-isolator, etc.

Do a methodical search and you'll find it.

That, and/or make like Jimmy Durante and follow your schnoz - if a
component has met an electrically violent end, the nose knows. Stuff
your proboscis in there and take a deep sniff, and track down the
crispy critter.

Jon Elson wrote:
There are a bunch of Molex connectors on
the boards. I have had a lot of trouble with this connector
type in rough environments. My machine is in the basement, but
if yours is in the garage or whatever, I'd definitely pull and
reseat every one of those connectors on the PC boards behind the
control panel. It just hinges down for easy access. That may
well fix the problem.



Use contact cleaner, instead of just reseating them.

Michael A. Terrell wrote:
Jon Elson wrote:
There are a bunch of Molex connectors on
the boards. I have had a lot of trouble with this connector
type in rough environments. My machine is in the basement, but
if yours is in the garage or whatever, I'd definitely pull and
reseat every one of those connectors on the PC boards behind the
control panel. It just hinges down for easy access. That may
well fix the problem.



Use contact cleaner, instead of just reseating them.


Yes, that might be a good idea. The boards are coated with some
horrible conformal glop, and the Molex housings are plastic.

I'd be afraid that some contact cleaners would dissolve the
conformal coat into a mess, or make the connector housings
brittle. i've seen that happen. But, a mild contact cleaner
might make the fix last longer. Once those tin Molex contacts
start to corrode, it becomes more and more troublesome.

And I have seen high voltage silicone insulation get the wire
zapped from inside it without opening at all -- the insulation just
turns limp in certain areas. Not too sure how many welders would be
using that insulation -- it was rather uncommon and expensive when I was
using it at work -- and we were normally routing 45KV with it, a bit
beyond what you would see in the typical welder.

If they are real molex connectors they won't melt. Styrene and
similar plastics are the ones damaged by crappy contact cleaner, and I
haven't seen any of it in over 35 years.


Well, the problem is that a heavily-used welder has been

The contacts can be replaced on the .093" & .062" series connectors.
generally, by the time the contact resistance goes up, the heat burns
away the tin plating.
Replacing the contacts on the cable end is not that hard.

Michael A. Terrell wrote:


If they are real molex connectors they won't melt. Styrene and
similar plastics are the ones damaged by crappy contact cleaner, and I
haven't seen any of it in over 35 years.


Well, the problem is that a heavily-used welder has been
subjected to TONS of Ozone, and that has a bad effect on
plastics. I could tell from the general condition that my
welder had been pretty lightly used - how lucky for me.

The contacts can be replaced on the .093" & .062" series connectors.
generally, by the time the contact resistance goes up, the heat burns
away the tin plating.
Replacing the contacts on the cable end is not that hard.
Replacing bad contacts on the BOARD end could be difficult,
especially with the back of the board glopped with conformal
coating. There are an amazing number of these connectors on
these boards. (They might be AMP Mate-n-Lock, not Molex, but
they are quite similar.) Most of these are signal connections,
so they won't burn up, just cause malfuctions. I've seen the
connector shells melt in other equipment that was running
serious current in them, though.

Gunner Asch wrote:
]

Thats what Im going to check tommorow. Oddly enough..it works fine in
AC stick mode.

The moment I put it to Tig, or DC stick, its full bore balls to the
wall. What the manual calls Stick Blast.

After posting the previous and reading some posts, I reread the manual
went back out and set everything to stick default, removed the pedal
and got it to work on AC stick normally.

But any DC mode and its 300 amps even though the amp meter reads 111

Oh, this is different than what you originally described. Well, if the
current control is OK on stick mode, then most of the really expensive
stuff must be OK.

The first thing I'd do is flip every panel toggle switch 20 times to clean
up the contacts. See if that helps at all.
I'm pretty sure there are microswitches or something similar that tells
the electronics where the AC/DC polarity handle is set, they may need
exercising, too.

This sounds like two different symptoms, at least. The current meter
doesn't read right at the low end, and the current control isn't working
right in TIG mode. Of course, there really is little difference between
the TIG and stick modes except open-circuit voltage. There are a bunch of
Molex connectors on the boards. I have had a lot of trouble with this
connector type in rough environments. My machine is in the basement, but
if yours is in the garage or whatever, I'd definitely pull and reseat
every one of those connectors on the PC boards behind the control panel.
It just hinges down for easy access. That may well fix the problem.

Jon