Powcon has been out of business for quite a few years.
http://www.arc-products.com took over from Powcon to maintain the existing units and apparently sells rebuilt units.
From what I've been able to gather:
SS is the basic stick unit (High/Low, "weld power" & on switch).
SM is the MIG version with a single range, "short arc puddle control" (slope control?), and a remote socket - I assume it's CV instead of CC.
ST is the TIG version with High/Medium/Low, "hot start", gas valve/fittings and a remote control socket.
The 300s are single/3 phase, 230/460 VAC, DC Inverters.
I garnered this info while looking for an inexpensive lightweight TIG unit for myself. Aluminum is much easier with a square wave inverter. Older square wave inverters have nowhere near the capability of new ones.
Thanks Scott for the info. I assume the 300 sm has a process switch position for stick, in which case I assume the unit then operates in CC mode. Has anyone used this unit for Tig, and can one put an HF unit on it without destroying the electronics?
I would choose the sm if it can do Mig and is also good for Tig (I have external gas solenoid,) whereas the st cannot do Mig. Am I correct?
The only reason I mention Powcon is that there seems to be an abundance of used units available on Ebay.
I think you are correct - SM if you want to MIG.
And I don't know why I listed as single range - it does have high/low ranges.
Powcon makes a pulser that runs up to 250 pulses per second and is usable on the 300 series so I don't *think* that an HF unit would cause any problems on this DC inverter. I would check with the manufacturer of the HF unit.
A constant HF could possibly affect the SCRs in the DC rectifier? (powcon doesn't use IGBTs). Have heard rumours that it can happen but haven't substantiated any of them. There are different types of inverters, different types of HF units.
ebay is the reason I looked into the powcons myself.
for the record I'm a sculptor not a welding professional. Use mainly stick and TIG for fabricating and working with castings - bronze, stainless, titanium and aluminum. Ocassionally MIG steel for mold reinforcement.
I own a 400 smt with a pulse pendant. This machine is only rated at 200 amps on single phase input, so you are a little limited on your pulse peaks for mig welding. The unique thing about the pulse pendant is that it can be used for mig or tig. This machine makes an excellent portable TIG unit for direct current applications (steel, stainless, etc) but is not suitable for aluminum tig welding because you need alternating current. I think it would be a waste of money to purchase a Hi-freq unit for this machine, as the lift start feature will work fine for DC work. Miller makes a compatable foot pedal for this machine. I have a split control cable that goes to the pulse pendant and to the foot pedal. Good luck
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