dj,
Our shop recently dug out an old Wisconsin-driven Hobart thats older than I had ever seen (It's a university/state funded shop, so there is no telling what all we have that has been lost in the paperwork). I am guessing it was somewhere from about the 50's or 60's. I know that an engine driven is completely different from a TIG, but here was our problem- Once we got the engine running (there is no telling how long it set unused) I had trouble with the rheostat--setting the machine on 100 amps danged near killed the engine and produced an arc similar to a nuclear explosion, but setting it around 20 amps was just about right for 1/8" 6010 or 3/32" 7018. Kinda weird, but since we don't do but a little bit of fab outside of the shop, I could get used to it. However, once on sight welding on some channel iron for stairs and catwalks, I found the voltage just didn't seem right--it was extremely difficult to maintain the arc, and there seemed to be no happy medium between full-nuclear and down-feather soft. I figured that this was simply because of the true DC (generator) and went on. After a number of hours of use, it has become much easier to maintain the arc but rheostat settings are still way off.
I say this because I have heard of old SA-200's that had a similar problem with the voltage that was fixed by simply connecting the stinger and ground together and bogging the engine (the way I understood it was it "burnt" whatever was interfering out, but I have no clue what it actually did), and the machine ran fine afterwards. I figure those old TIGs may be set up in the rectifier somehow similar. Setting the machine at what you actually think the amperage should be could be actually setting it way too high due to some mechanical inconsistency and melting your tungsten, and setting the amps lower may not quite produce the voltage needed to actually weld like you want it. I'm sure that there is probably a better way to fix the voltage problem than to run a closed circuit like I have heard about on the SA's, maybe something like simply blowing out the internals and cleaning them up, and just mechanically readjusting the rheostat to the right place.
I as well would appreciate any info or confirmation of this practice, and if anyone has had a similar problem like I stated above, I am well open for suggestions, even if after reading this you just have to sit back and shake your head. That being said, I gotta admit that the old Hobart produces one of the purdy-est arcs I have ever seen, albeit in the wrong settings.
Thank you all in advance and good luck, dj, on that old machine!
G. L.
How is the polarity changed on this machine? Is it a switch or does it require swapping the leads?
