Butch,
The PC idler board only serves to idle the machine up and down. Welding RPM for the engine is about 1550, not sure of the exact rpm.
It is supposed to operate like this:
When you are not welding the idle solenoid is energized and it pulls in the solid metal bar. This action overcomes the spring of the governer that hold the carburetor open and at a high idle.
When you strike an arc the solenoid loses its ground through the action of a reed switch and the metal bar in the soldenoid is released. The governer springs then force the throttle open and brings the engine up to welding rpm.
When you stop welding the solenoid gets a ground again and energizes the idle solenoid, which pulls the metal bar in and the engine idles down. The pc board only operates the idle. If you have 120VDC you are operating at high idle.
You have 120 VDC so your exciter circuit is working. There are main brushes for the armature that are very similar to the exciter brushes. They are under a cover. If you have a long hood welder you may have some difficulty getting to them. Once you access them make sure they are not stuck in their holders. They are carbon so don't pry on them or they will shatter.
The very worst problem you may have is a problem with the shunt coils.
It could also be a problem with the wire that connects the shunt coils together.
So to troubleshoot:
1. Check main armature brushes to see if they are stuck in their holders.
2. Use a meter to check the ohms of the shunt coils. (google search)
3. If the ohm check fails for the shunt coils check the wire that connects the shunt coils for continuity  |