XMT 304 CC/CV v-sense mode

[ArcTan]

Hi,
I've been using my new to me XMT 304 with my Hobart Hefty feeder and occasionally have an issue with the XMT seeming to "sleep" when I stop running a bead. I have it set on v-sense feeder, say at 18 volts or so, and the display will normally alternate between 18 and 80 (or something in that range). When I start welding of course it'll show the actual voltage. Occasionally when I release the gun trigger, it'll stop making the quiet "hum" noise, and the display will alternate between 18 (or whatever I have it set at) and a much lower number like 4 or 5. When this happens, it won't weld when I pull the trigger and I have to either cycle the power switch or switch it to stick and back to v-sense. Then the hum comes back and I can weld normally again. I can't seem to find a pattern to it, and it hasn't given me any trouble on stick mode so far. The fan will cycle on and off as needed. Any ideas?
Thanks!

[ccawgc]

The 80 equals the open circuit voltage of the welder. If this drops to 5 the inverter has turned off. and your question is why? Could be either the front panel pcb or the control pcb. The fact it starts working when you switch to stick and back makes me lean towards to the front panel. You can try this. jumper socket A and B in the 14 pin plug after setting the welder to MIG. this will turn the output on. if it stays on and you have no problems then the front panel switch is failing. Your call on what to repair. Most pcb repair facilities will not touch these pcbs because of the micro processor on the pcb.

[ArcTan]

Ok, thanks. I will try that.

[ArcTan]

So far it seems to be working fine on MIG mode with the jumper. I'll have to dig into it a little more.

[ccawgc]

If it works with the jumper and still doesn't in VS then the selector switch on the pcb may be failing.

[David Boone]

Apparently, the problem is really in the pcb. I doubt that someone will officially undertake to repair the micro processor on the pcb with a guarantee, so maybe you should find someone who will do it at your own risk.

[ArcTan]

Interesting. Do you have a lot of experience with these welders? I don't really know much about them or their repair.

[ccawgc]

Most pcb repair places have given up trying to repair them. I sent one in with just a display problem and got back a dead pcb. They tried to over repair it and killed it.
There is a micro controller and software on the UI/display pcb.
Might still be able to get a get one. depends on which version you need.