Lincoln Square Wave 300 manuals ?

Hello,
I've got this Lincoln Square Wave 300 welder, and it needs a little work. I downloaded the user manual from Lincoln, but it only goes
so far. I think there are a couple of capacitors in some of the timing circuits that need to be replaced. (For instance, if you set the postflow timer over 10 seconds, it really leaves the gas on FOREVER. I've already wasted $10 of argon with this.)
I notice Miller puts the complete electronic schematics of their machines in their manuals, very unusual! Is there any place to get schematics for the Lincoln machines? Or, any place I can just find out which capacitors are in which timer? (I can trace all this out, but it would take more than a few hours, though.)
Thanks much in advance!
Jon
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I'd suspect the pots first, esp. since the shafts stick out and invite mechanical damage. What you describe could just be a break in the carbon film at the 10 sec point. A break would also change the overall behavior, not just past the break.
All these micro toggle switches and pots give me the willies, sticking out the front of a machine in a shop with heavy stuff banging around everywhere. Ought to come with a protective cage for the front.
Bob
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Bob Powell wrote:

This would be easy to check, but I don't think so. It is not a sharp discontiuity, but the time gets exponentially longer the closer you get to the 10 second mark. IE the min setting is 5 seconds, the 5 second setting is 15 seconds, and the 10 second setting is 30 or so. Sounds exactly like a leaky electrolytic capacitor.

This machine has a shop-made set of hangers for the TIG hoses/cables, and they pretty well protect the control panel. Lincoln didn't use micro switches or pots on that model, either. They didn't have to, as the whole machine is HUGE!
Jon
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Bob Powell wrote:

Well, it WAS the capacitor, as I suspected from the symptoms. It was a 100 uF Tantalum capacitor, notorious for failing after a period of disuse. I replaced it with an Aluminum capacitor, and the timing is now right on the button.
I'd still like to get complete schematics, this is a more complicated machine than I had guessed. There are 6 circuit boards behind the control panel, and a couple of them are pretty complicated.
Jon
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Jon Elson wrote:

I just got what Lincoln would send me. It is a WIRING diagram of the machine, not a SCHEMATIC. All the boards are just rectangles with wires connected to them. So, I guess I'm going to have to trace out the boards on an as-needed basis. UGH! I was surprised Miller gives complete schematics of their boards, I wish Lincoln did the same.
Jon
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