On Mon, 26 Dec 2011 21:23:56 -0600, Jon Elson
wrote:

Does anyone have a schematic of the circuit boards in a Lincoln
Square Wave TIG 300? I have what Lincoln releases to to public,
which is just a wiring diagram of the whole machine. All the
PC boards are just squares on the drawing.

When I got it (used) I was able to trace down the bad Tantalum
capacitor that caused the shield gas postflow to stay on
forever. Now I have a more difficult problem to solve.
When the machine is first turned on after a period of not
being used, I can't get any arc current. It indicates 72 V
and 0-7 Amps on the LED meters, even if the electrode is
shorted to the ground clamp. The high frequency works like
mad, but there is no main arc current. It seems to take
10-15 minutes of trying, and suddenly jumps to life. This last
time I fiddles with the switches again, and that's when it started
working, so it could be a dirty contact in the HF start/always/off
switch. But, in previous cases it just started working at one
point with no flipping of switches.

Has anyone else seen a similar problem with a Lincoln square
wave TIG machine? I am suspecting another bad capacitor, but
it would be hard to track down without detailed schematics of
the boards.

Thanks for any hints in the right direction.

Another problem is the torch is getting plugged up and I have to
run the cooler for minutes before there is just the most meager
flow. The outlet from the cooler is plenty strong. Is there something
I can put in the torch to flush it out? (I discovered the tank in the
cooler had slowly evaporated, and was really low. I added a bunch
of water. next time at the welding place I will get a new batch of
cooler fluid and replace.) I filled it originally with this greenish stuff
specifically sold for TIG coolers.

Thanks, again.

Jon


I recently gave one one of those away. Mine would preform normally on
AC..but when swtiched to DC..no matter what the setting..it was 300 amps
at the torch. No matter the polarity...300 amps at the torch.

Yet AC worked just fine.

The guy I gave it to does mostly aluminum, but says he will have it
looked after..one of these days.

I may..may have the schematics for it..Ill check

Shrug

Gunner

One could not be a successful Leftwinger without realizing that,
in contrast to the popular conception supported by newspapers
and mothers of Leftwingers, a goodly number of Leftwingers are
not only narrow-minded and dull, but also just stupid.
Gunner Asch