XMT 350 prepower pc1 control board RC3 troubleshooting

[Gmoney44]

Ok that what I was assuming so I'm not seeing anything different when I unplug hd1 so I guess I have something bad on pc1

[jjohn76]

Hd1 = lem

[Gmoney44]

Lem?

[ccawgc]

From command ground the 4 wire to the lem should read +15 and -15 and 0 and 0 the minus might read -14.4.
If different unplug lem and retest pc1 supply to LEM if voltage jumps up Lem is bad. if it stays low then pc1 is damaged. might also
have something else pulling the voltage down. if only the LEM is bad you should get output with LEM unplugged. OCV. current will go to max if you try to weld.
Also check feed back wires where they connect to the weld terminals.

[Gmoney44]

Also when I do engaged the ocv on board I show 14v on display. And 14v and -5v on hall

[Gmoney44]

Not sure if i did this right but I unplugged c9 and got 0 reading on harness end of hall sensor and same 2v and -10 readings on the board pins.

I do not have ocv engaged on the board but if that doesn't matter for what your thinking 1997cst, how exactly do I get a reading the ocv, I'm not seeing it in my manual.

[1997CST]

What's your OCV?

[Bushytails]

If you unplug the hall effect sensor and the voltages are still low, then it is not the problem.

You might be able to find the bad component by seeing if anything is getting hot. One of the two big heatsinks on the top board is going to be hot, and something else, somewhere, might also be hot. If you do this by poking things to see if they're hot, make sure the unit is unplugged and the capacitors verified discharged first.

[Gmoney44]

Thanks jjohn and bushy. I am finally getting back to troubleshooting this machine. I decided to just power it up, Ive got a amp reading and will adjust on meter but Volts will spike initially then drop to .2. verified reading is correct with dmm. Checked supply voltage on hd1 and I have -10v (specs -15v) and 2v (specs 15v). according to manual its either the hall transducer or pc1 board? Is there a easy way to narrow down whether its the hall transducer vs the pc1 board? Would I be correct in thinking If i just unplug rc9 @ pc1 and I read spec voltage its the pc1 and if not its the hall device?

[jjohn76]

My tech manual has a separate note in the PC1 and PC2 pre power checks to remove plugs before testing.

[Gmoney44]

Yours says to do that for all prepowers checks? Mine says only on the pc1 tests.

[jjohn76]

I went back through my Tech Manual, which is older than yours. Mine says to remove all plugs before checking measurements, which I didn't see in the screenshots of the manual you show. Like Bushy said, it doesn't throw up any alarms, but it may be worth a call to Miller Tech to confirm.

[Gmoney44]

I have not plugged it in to run it yet. I was concerned I might do more damage.

[jjohn76]

What is the problem with the machine?

[Bushytails]

I would figure that's close enough, and look for the problem elsewhere.