Hi. I recently purchased a used Millermatic 350 that has issues. It is incapable of striking an Arc. The actual output voltage measured on either the output terminals or on the wire feeding out of the gun to the ground clamp matches the voltage selected on the display, in my case I tested at 21.0vdc however if the wire touches ground it immediately drops to 0-0.2vdc (My understanding is that the voltage should be much higher than displayed until an arc is struck and then should match the display).
I downloaded a technical manual and have performed the pre-powerup tests, these are my results. Testing done with a Fluke 789 process meter
Output Diode Check:
meter neg to output pos, meter pos to output neg: 1.014kohms
meter pos to output pos, meter neg to output neg: Shifts between OL and 2.67kohms
(I find it odd that meter polarity in the ohm position changed results)
D1:
Forward bias (meter in diode test mode): (Upper Diode) 0.170vdc
(Lower Diode) 0.170vdc
Reverse bias (meter in diode test mode): (Upper Diode) OL
(Lower Diode) OL
Forward bias (meter in ohm mode): (Upper Diode) 5.43kohms
(Lower Diode) 5.41kohms
Reverse bias (meter in ohm mode): (Upper Diode) Shifts between OL and 9.2kohms
(Lower Diode) Shifts between OL and 9.2kohms
D2:
Forward bias (meter in diode test mode): (Upper Diode) 0.168vdc
(Lower Diode) 0.168vdc
Reverse bias (meter in diode test mode): (Upper Diode) OL
(Lower Diode) OL
Forward bias (meter in ohm mode): (Upper Diode) 5.32kohms
(Lower Diode) 5.34kohms
Reverse bias (meter in ohm mode): (Upper Diode) Shifts between OL and 9.0kohms
(Lower Diode) Shifts between OL and 9.0kohms
Input Rectifier Check:
(3) to (L1-1) Forward bias (diode test) 0.422vdc Reverse bias (diode test) OL
Forward bias (ohm mode) 4.22Mohms Revrese bias (ohm mode) 4.22Mohms
(4) to (L1-1) Forward bias (diode test) 0.421vdc Reverse bias (diode test) OL
Forward bias (ohm mode) 4.20Mohms Revrese bias (ohm mode) 4.20Mohms
(5) to (L1-1) Forward bias (diode test) 0.418vdc Reverse bias (diode test) OL
Forward bias (ohm mode) 4.18Mohms Revrese bias (ohm mode) 4.40Mohms
(3) to (C1 (PM1) ) Forward bias (diode test) 0.418vdc Reverse bias (diode test) OL
Forward bias (ohm mode) 4.17Mohms Revrese bias (ohm mode) 4.18Mohms
(4) to (C1 (PM1) ) Forward bias (diode test) 0.419vdc Reverse bias (diode test) OL
Forward bias (ohm mode) 4.16Mohms Revrese bias (ohm mode) 4.17Mohms
(5) to (C1 (PM1) ) Forward bias (diode test) 0.419vdc Reverse bias (diode test) OL
Forward bias (ohm mode) 4.39Mohms Revrese bias (ohm mode) 4.16Mohms
Capactitor Check:
C3: Starts around 290kohms, climbs to around 3900kohms, then quickly stabalizes to 1.02Mohms
C4: Starts around 290kohms, climbs to around 3900kohms, then quickly stabalizes to 1.02Mohms
Resistor Check:
R11: 41.8ohms R12: 42.4ohms
PC2 Diode Check:
D1:
Forward bias (meter in diode test mode): 0.327vdc
Reverse bias (meter in diode test mode): 0.433vdc
Forward bias (meter in ohm mode): 1.984kohms
Reverse bias (meter in ohm mode): 1.984kohms
D2:
Forward bias (meter in diode test mode): 0.326vdc
Reverse bias (meter in diode test mode): 0.433vdc
Forward bias (meter in ohm mode): 1.984kohms
Reverse bias (meter in ohm mode): 1.984kohms
IGBT Check:
PM1:
C1 to E1: 77.1kohms
C2 to E2: 77.1kohms
E1 to PLG5(10): OL
E2 to PLG5(7): OL
PM2:
C1 to E1: 77.1kohms
C2 to E2: 77.1kohms
E1 to PLG5(6): 99.8kohms
E2 to PLG5(9): 99.8kohms
The conclusion I have drawn from these tests are that both diodes (D1 and D2) on the PC2 board are failed and IGBT PM1 is also failed. I'm looking for some thoughts and advice from anyone with some experience about my conclusions and if this seems plausible as the cause of my issues before I source replacement parts.
Thanks
I downloaded a technical manual and have performed the pre-powerup tests, these are my results. Testing done with a Fluke 789 process meter
Output Diode Check:
meter neg to output pos, meter pos to output neg: 1.014kohms
meter pos to output pos, meter neg to output neg: Shifts between OL and 2.67kohms
(I find it odd that meter polarity in the ohm position changed results)
D1:
Forward bias (meter in diode test mode): (Upper Diode) 0.170vdc
(Lower Diode) 0.170vdc
Reverse bias (meter in diode test mode): (Upper Diode) OL
(Lower Diode) OL
Forward bias (meter in ohm mode): (Upper Diode) 5.43kohms
(Lower Diode) 5.41kohms
Reverse bias (meter in ohm mode): (Upper Diode) Shifts between OL and 9.2kohms
(Lower Diode) Shifts between OL and 9.2kohms
D2:
Forward bias (meter in diode test mode): (Upper Diode) 0.168vdc
(Lower Diode) 0.168vdc
Reverse bias (meter in diode test mode): (Upper Diode) OL
(Lower Diode) OL
Forward bias (meter in ohm mode): (Upper Diode) 5.32kohms
(Lower Diode) 5.34kohms
Reverse bias (meter in ohm mode): (Upper Diode) Shifts between OL and 9.0kohms
(Lower Diode) Shifts between OL and 9.0kohms
Input Rectifier Check:
(3) to (L1-1) Forward bias (diode test) 0.422vdc Reverse bias (diode test) OL
Forward bias (ohm mode) 4.22Mohms Revrese bias (ohm mode) 4.22Mohms
(4) to (L1-1) Forward bias (diode test) 0.421vdc Reverse bias (diode test) OL
Forward bias (ohm mode) 4.20Mohms Revrese bias (ohm mode) 4.20Mohms
(5) to (L1-1) Forward bias (diode test) 0.418vdc Reverse bias (diode test) OL
Forward bias (ohm mode) 4.18Mohms Revrese bias (ohm mode) 4.40Mohms
(3) to (C1 (PM1) ) Forward bias (diode test) 0.418vdc Reverse bias (diode test) OL
Forward bias (ohm mode) 4.17Mohms Revrese bias (ohm mode) 4.18Mohms
(4) to (C1 (PM1) ) Forward bias (diode test) 0.419vdc Reverse bias (diode test) OL
Forward bias (ohm mode) 4.16Mohms Revrese bias (ohm mode) 4.17Mohms
(5) to (C1 (PM1) ) Forward bias (diode test) 0.419vdc Reverse bias (diode test) OL
Forward bias (ohm mode) 4.39Mohms Revrese bias (ohm mode) 4.16Mohms
Capactitor Check:
C3: Starts around 290kohms, climbs to around 3900kohms, then quickly stabalizes to 1.02Mohms
C4: Starts around 290kohms, climbs to around 3900kohms, then quickly stabalizes to 1.02Mohms
Resistor Check:
R11: 41.8ohms R12: 42.4ohms
PC2 Diode Check:
D1:
Forward bias (meter in diode test mode): 0.327vdc
Reverse bias (meter in diode test mode): 0.433vdc
Forward bias (meter in ohm mode): 1.984kohms
Reverse bias (meter in ohm mode): 1.984kohms
D2:
Forward bias (meter in diode test mode): 0.326vdc
Reverse bias (meter in diode test mode): 0.433vdc
Forward bias (meter in ohm mode): 1.984kohms
Reverse bias (meter in ohm mode): 1.984kohms
IGBT Check:
PM1:
C1 to E1: 77.1kohms
C2 to E2: 77.1kohms
E1 to PLG5(10): OL
E2 to PLG5(7): OL
PM2:
C1 to E1: 77.1kohms
C2 to E2: 77.1kohms
E1 to PLG5(6): 99.8kohms
E2 to PLG5(9): 99.8kohms
The conclusion I have drawn from these tests are that both diodes (D1 and D2) on the PC2 board are failed and IGBT PM1 is also failed. I'm looking for some thoughts and advice from anyone with some experience about my conclusions and if this seems plausible as the cause of my issues before I source replacement parts.
Thanks
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