Greetings again from the newbie workshop.
I purchased a Lincoln Idealarc TIG 300/300(vintage 1984) before the
holidays. Came with an LN-7 mig attachment, but no welding cables,
interconnect cabling, torch, or foot pedal. For $200, I couldn't pass
it up! I've since scrounged all the goodies to make it operational and
after some help from the group in a previous post, it seems to be
The problem I'm having with it is remote control of the welding
current. When the switch is up for local control, it seems to be fine
although I find the control a little touchy. For example "3" might not
produce a good bead and "5" will blow a hole. I'm still chalking this
up to technique.
When the switch is set to remote, I should be able to control the
welder from minimum current to the maximum of what the front panel
control is set to. If the front panel is set to "6", the foot control
will operate from 0-6. The problem is, it doesn't. The foot pedal
will start the welder, but increasing the pedal does nothing. The
pedal is homemade, but it has the correct 10k ohm pot in it.
Interestingly enough, the LN-7 unit can't control the welding current,
I dug out the manual for it and started tracing back the circuitry.
The front panel control is a 5k ohm pot. That's routed thru the
local/remote switch to the power control pc board. I pulled the
connector off the board and stuck the ohmmeter into the two terminals
coming from the switch. The wire numbers are 208 and 242. As I
increase the front panel control, the resistance goes from 5k at "0" to
zero ohms at "10". I'll buy that. When I flip the switch to remote
and the front panel control is at "0", I read 10k(the value of the pot
in the foot pedal). Increasing the foot pedal does nothing because the
front panel switch is at "0". Ok, crank up the local control to "10".
Now the pedal will swing from 10k to 0 ohms. The only problem is half
the pedal travel is used up just to get to 5k. The welder thinks
everything is still at "0" because the resistance is 5k or higher.
Does that make sense? I have the exact same problem with the LN-7
I built the pedal myself as well as the interconnect cable to the
LN-7, so whatever I did(if it's wrong), it's common to both. Any
*NOTE: I just checked on the Lincoln website and they show on one of
their TIG 300/300 schematics, the remote control pot being 5k. Ok,
that explains that, but then why is the LN-7 wrong?? Again, thanks for
17 years ago