Problem On Old Sa-200

[billysol]

I have an old SA-200 (2365 Code). I cranked it up the other day and it was at idle. I turned the fine adjuster up to 100 and burned the reostat out. I thought I found and fixed the problem( Temp Gauge tube shorted to reostat). Bought a new reostat fro Weldmartonline.com and instaled it. Same problem engine at idle turned the adjuster to 100 burned reostat. I am in the process of changing out the whole generator with another (2955 Code). The only thing I can figure is a insulation breakdown in the Welding Shunt Coil at full exciter voltage. Anybody else ever had this problem even on a newer code machine?

Please email me if you have and what was found to be causing it.

billysol@alltel.net

Thanks

Bill

[Zrexxer]

I have an old SA-200 (2365 Code). I cranked it up the other day and it was at idle. I turned the fine adjuster up to 100 and burned the reostat out. I thought I found and fixed the problem( Temp Gauge tube shorted to reostat). Bought a new reostat fro Weldmartonline.com and instaled it. Same problem engine at idle turned the adjuster to 100 burned reostat. I am in the process of changing out the whole generator with another (2955 Code). The only thing I can figure is a insulation breakdown in the Welding Shunt Coil at full exciter voltage. Anybody else ever had this problem even on a newer code machine?

Please email me if you have and what was found to be causing it.

billysol@alltel.net

Thanks

BillI don't know what's causing your problem, but call WeldMart up where you got the rheostat and talk to Larry, the owner... he's very willing to help and seems to really know these machines. 800-460-6474.

[ventureline]

check for a short to ground off the 2 wires going into the rheostat, also make sure that "new" rheostat was a 64 ohm 150wt unit. If you did short out the old rheostat with a "temp gauge" the likely hood of smoking one of these wires would be great. Sounds as well that you have no fuse protection.

There is really very little room to put a temp guage anywhere near the local rheostat, how did you manage that?

Not likely to be a main generator issue, most likely an exciter stator coil if anything.

[billysol]

Well I have talked to Larry several times and he has sent me drawings via email. By looking at the drawings there is not much place for a short except in the WELDER SHUNT Coils. There was no fuse in the machine originally. I am in the process of rewiring the machine now to get rid of the old cloth covered wire as much as I can. I have been running this machine for about 8 or more years with no problems. This problem came on real sudden the other week.

When I found this machine in a junk yard in 1997 or so with a bad engine I changed the engine over to a PERKINS 4.108 Diesel. It was a fairly simple change.

I was able to put a Temperature gauge and an Amp meter and Hour meter plus a couple of warning lights for no oil pressure and high temperature. I also have kill switches in the oil pressure line and in the head to kill the engine if I lose oil pressure or go over 225F on the coolant.

When I burned the reostat I found the Temperature sensor tube burned so I figured that it shorted the wiper arm of the reostat. I don't think that was the problem since the new reostat burned in about 10 seconds and I checked the wires.

The one thing I found this afternoon that I am very much concerned about is in the bottom of the main generator just under the brushes was some oil and diesel fuel and the wire tying the 2 shunt coils together was laying in it. Also to add insult to injury right where the oil and fuel was there appears to be a old tape wrapped splice so this may have been my short. In the morning I am going to replace the old wire between the shunt coils and also I will drill a drain hole in the generator housing to keep this from happening again.

Will post the results when I find if the solved my problem or not.

Bill

[ventureline]

Your power to the shunt coils originates from your exciter stator, never the less just meter your shunt leads together and to ground, the only way to blow up the Rheostat is if one of your shunt leads has shorted to ground

[billysol]

Your power to the shunt coils originates from your exciter stator, never the less just meter your shunt leads together and to ground, the only way to blow up the Rheostat is if one of your shunt leads has shorted to ground

Well the right (+) brush feeds the shunt coil and the wiper arm of the reostat. The end of the windings of the reostat goes to the left brush (-). If I remeber my DC theory right the POWER flows from NEGITIVE to POSITIVE so really the left brush sends the power to the reostat and is taken off by the wiper and goes through the shunt coils and then to the right brush.

I have tested the leads to ground with an ohm meter and also with a 12 volt battery and light bulb and they checked out good. I will try again in the morning with 2 batteries in series wich will be 24 volts and see if I can find a breakdown in insulation. I am still of the mindset that the splice laying in the fuel and oil broke down at the higher voltage when I turned the reostat to 100 and put full voltage on the wire splice. I have thought about using 120 volt AC to meg the wires. Hook one side of the 120 to the right brush holder and then use a lamp with a probe to check to ground which would give me enough resistance to prevent burning something up if I do have a leak. I can make the stuff to do this without putting myself in danget of shock.

Bill

[ventureline]

You must be right, as I'm only looking at the service manuals electrical and block diagrams

[billysol]

Well I asked Larry at Weldmart if a Service Manual was available and he said NO They never made one for the old Short Hood SA-200. This Machine is a 1953 model. I down loaded the Operator Manual from Lincoln and it has part numbers. From what I can put together all the SA 200 below 3400 CODE number are pretty much the same. I have 2 SHORT HOOD the one I am having problems with is a 2365 CODE which is a 1953 and I have a 2955 CODE which is a 1955 model.

I have the generator out of the 2955 and was going to put it behind the Perkins but the wire or shunt is open so I have to try and fix the 2365 as I can't spring for the $430 plus shipping for a new set of shunt coils at this point in time.

Bill

[ventureline]

Well if you disregard the idle board in the Classic 1, the wiring diagram is the same...

[billysol]

Well I used 120Volt AC to "MEG" The Shunt coils and wiring on the 2365 CODE machine for shorts to ground and they were all OK. Now this was after I moved the wire splice that was laying in fuel and oil. I am replacing all the cloth covered wire I can with good plastic covered wire and soldering the joints and shrink tubing them. I ordered new exciter brush holder insulators from weldmart.com so they should be here Monday or Tuesday. I should have the generaator back in frame and hooked back to the engine by then so All I have to do in install the new insulators and test it out.

As soon as I get the 2365 going then I will try and find the open in the shunt in the 2955 Machine and maybe be able to repair it.

I'll keep this up to date as I go along.

Bill

[billysol]

Well I have replaced all the cloth covered wire I could get to. I have the generator back in frame and bolted back to the engine.

I was making progress to be able to crank it up and run it maybe today. The clutch in my truck went bad last night and I had to get a tow home and I spent today dropping the trans and chasing parts for the clutch job so didn't work on the welder. I have to go to Dothan Al tomorrow and get the new clutch plate and install it to get my truck back on the road.


Bill

[billysol]

Well I have rewired the 2365 Generator as best I can. The old cloth covered wires were naked in a lot of places. I cut them and slid "Shrink Tube over them where I couldn't replace. I replaced what I could reach with good plastic insulated wire.

I have re-installed it in the frame and have cranked it up. I have some wires hooked up wrong on the exciter to reostat to aux plug. I will be re-doing them in the morning. I only have 1 point 5 volts between the exciter brush holders. Needless to say that ain't enough. Larry at weldmartdotcom emailed me a new drawing and I see where I made my mistakes.

I will post again when I have more news and also the time.

Bill

[billysol]

Well I got the 2365 up and running today. I had to do some swaping of exciter field coils and exciter armateur with the 2955. Once I put the coils and armateur from the 2955 machine I had exciter voltage. I also ran 2 wires directly from the exciter brush holder to my aux plug and this gives me 120 volts DC to run my grinders and doesn't affect the welding generator. I was having a problem getting the wireing right on the aux feed and didn't have enough power to run my Black Decker 9" grinder now I do have the power.

I guess I will call weldmart and get a set of coils to go in the 2955 machine when I get the diesel engine mounted and running.

I still don't know for sure what started this whole mess. I rather think that it was the old cloth covered wire that Lincoln used when the built these machines back in the 1950's. I found several bare places and a couple of old "friction tape" covered splices. One place in the welder shunt wire looked like it had shorted to ground which I guess would have taken out the reostat. Anyway it's running my grinders and welding like it should now.

Bill