Page Checking Bus Voltage Imbalance Turn off unit and wait for voltage to drop to near 0 zero volts accord- ing to Section Prior to Serial No. KK, reconnect plug 12 to receptacle 3.
Reinstall case. Page Section 10 - Electrical Diagrams The following is a list of all diagrams for models covered by this manual.
Page 51 SC Figure Page 52 SC C Figure Page 53 Figure Page 54 Figure Page 56 Figure Page 58 Figure Page 60 Figure Page 62 Figure Page 64 Figure Page 66 Figure Page 68 SB Figure KK And Following Figure Page 69 SA Figure Replace with proper PCB assembly. Print page 1 Print document 78 pages. Rename the bookmark. Delete bookmark? Cancel Delete. Delete from my manuals?
Sign In OR. Don't have an account? Sign up! I say "appears" a lot because the circuit in my machine looks absolutely nothing like the circuit shown in my outdated manual, so I'm guessing Noticed the aluminum bar to the negative output post had been arcing.
Removed, wire brushed, re-installed. Now had Help 6 on powerup. All rails low due to the control transformer being linked for while running off Two clunks from W2 on powerup, with 2. W2 NO contacts still open.
Jumpered a battery to the contactor, clunk, but contacts still open. Pulled out the contactor block, unable to manually actuate W2. Unit now powers up, successfully links for , shows meters, etc. Capacitor charging seems correct, in that they smoothly charge to around V, the relay on pc1 clicks, then they suddenly jump to the final voltage.
Current meter is stuck at A. Found hall effect sensor is putting out 2. Appears to need a new hall effect sensor. But, should operate in CV mode Tried welding. Will make some sparks for about a second, then shuts down with a Help 6 for a fraction of a second, followed up by a fresh precharge cycle.
R7 or, rather, the substitute I have dangling on jumper wires gets mighty hot if you let it do this a few times. Measured line voltage at SR1 terminals, rock solid. According to the outdated manual I have, help 6 is triggered by low voltage on the 24vdc rails, which are derived from the 18vac taps.
Was going to measure the 24vdc rails, but it was getting dark and rainy, and my current work station is the driveway So, while waiting for weather that'll let me poke at it more, here's a couple questions I have: Can anything other than the low voltage lockout on the 24vdc rails trigger help 6?
For example, low voltage on the filter caps? I was going to measure them during a welding attempt next to see if they were holding solid.
I suspect many things have changed since the manual I found. Is it normal for these machines to have this many simultaneous problems? A mechanical contactor failure, a shorted fet or control issue in the lift-arc circuit which would usually result in pc1 being thrown out, I'd figure , arcing internal connections, an open power resistor, a failed hall effect sensor, whatever is causing the unit to shut down when I try welding, and who knows what I'll find next.
I bought miller because of previous good experience, but Any tips on where I should start looking for the helpwhile-welding issue? My current plan is to measure a few more voltages to see if anything is legitimately dropping too much while welding, and if not, try to determine if pin 14 is the only thing that triggers help 6.
Anyone have an accurate schematic for the lift-arc circuit on my serial number? A quick glance at the board looked like it was a driving Q39 with T3 and a couple freewheel diodes in a flyback arrangement, but I didn't analyze it fully. I don't see any feedback or obvious reason removing Q39 would do anything other than disable lift-arc functionality, but I'd still like to fix it, just in case I ever get the time to learn tig.
And, as I already said at least a couple times , anyone have a new service manual? Tags: None. You sir have done a lot of typing and I commend the effort. While I'm not able to offer any help or solutions to your problem, I will say your braver then most for trying, and your persistence will I'm sure pay off.
I hope it does. Comment Post Cancel. Is there any resistance between the contacts on your main power switch? You know, with that list of problems it almost sounds like that machine was left plugged in and there was a lightning strike close by. While it is not practical in an industrial environment were the welders may be direct wired, I make it a habit to ALWAYS unplug welders before leaving the shop for the day.
The schematic is also presented better too. Originally posted by jjohn76 View Post. Understood, even if you don't get it back, that manual has been helpful for any XMT troubleshooting, especially on the newer ones I have seen. My lift arc problem was actually on an older XMT Got a call from the LWS this morning A whole week shy of six months, even!
The excuse from the miller factory repair center, apparently, is that it never actually worked, because it was wired wrong from the factory, couldn't have ever worked, and it took them a while to figure this out. And I was born yesterday! Obviously, the welder with clear signs of use, worn contactor contacts, arcing-damaged negative output connection, full of dust, that I diagnosed multiple failures with, and that I made sparks with, had never worked a day in its life.
So, I'd say the first shop did something incompetent, put it back together wrong, and didn't want to own up to it. I'll need to rustle up some SO cord and another twistlock, then we'll see if they actually even fixed it Holy parts cannon, batman!
All three 3. PCBs are new. The power PCB is a slightly different design than the old one. New current sensor. Everything has been apart, including the end covers. Even things that haven't been replaced have been removed or disconnected, like the output diodes, as evidenced by some new screws.
Some of the stuff in the tunnel might have been removed and reinstalled, since the jackets have been cleaned up.
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