Hello All,
My name is Brian and I am a newbie here. I am a Master Electrician by trade and I love welding as a hobby. If anyone has any questions on electrical to feed a welding machine, feel free to contact me. I work on High Voltage down to electronics daily. I know these machines have alot of stored energy and my Fluke 87V and test leads are rated up to 1000vdc. I recently bought a Miller Maxstar200SD off an auction and I need some help. It needs a circuit board. I would like some help ensuring it only needs one board so I dont sink in too much money when I could have bought a new one. I greatly appreciate the help from anyone up to the challenge. I am guessing it needs a PC1 inverter board based on my findings below. I found out they have a revised PC1 inverter board/ part # for my machine. I dont want to stick a new PC1 board in the machine and smoke a new board. I found some troubleshooting questions on a Miller Maxstar 200stx but I am sure someone has more specific points I can test on the machine for a SD. Again, I appreciate any information from the experts on this site and I apologize for the long post.

Thank You,
Brian Gibbons

My Miller Maxstar 200SD general info.
Manuf. date 2004
owners manual (electrical block diagram)
currently wired for 120v 60hz for troubleshooting(once fixed it will be set up 240vac 60hz.)

My Test Equip. used:

Plug in and turn on machine you have no operator interface (no lcd screen for volts/amps/etc. You here a control relay clicking on PC2 power interconnect board. It is almost sound like it is calling on the inverter board to fire up or the next step but it never gets there. I was guessing a PC1 inverter board but I would like to be sure it is not the interface board or boost board or 2 or all bad. There is no signs of corrosion or burned spots on components on the boards and the parts inside we clean like it was used in a clean room.

Place line disconnect switch in On position
1)Check and replace line fuse(s), if necessary, or reset circuit breaker.
This all checks out tested imput voltage
2)Check for proper input power connections and check condition of power cord.
10/4 SOOW cord was visually inspected and ohmed out to validate continuity
3)Check inverter control board PC1 for proper seating.
PC1 inverter board is properly seated
4)Check weld control board PC3 for proper seating.
PC3 weld control/operator interface ribbon connections seated properly.
5)Check boost control board PC10 for proper seating.
PC10 Boost control board is properly seated.
6)Check continuity of Power switch S1 , and replace if necessary.
Continuity of power switch S1 is good.
7)Check bus voltage on power interconnect board PC2 receptacle RC5 replace
PC2 if necessary.
780volts DC on receptacle RC5 on board PC2

Check 15 volts dc supplies as follows

8)Disconnect plug PLG1 from RC1 on PC1 and check for 15 vdc. If 15 vdc is now present,
replace PC3.
This is the step that the STX must have less pins on the plug than the my Maxstar SD. There are 20pins (2rows of 10) that is labeled PLG1 that Plug into RC1 on PC1. This is the step that I need to find out which pins to test to find the +/- 15vdc
9)Disconnect plug PLG5 from RC5 on PC1 and check for 15 vdc. If 15 vdc is now present,
replace HD1.
This TESTED GOOD, no voltage present on RC5 of PC1.
10)Disconnect PC1 from PC2, and on PC2 check for 15 vdc between RC3 pin 5 and RC3 pin 8. If 15 vdc is now present, replace PC1. If the 15 vdc is still not present, replace PC10.
I get 19VDC. Does this mean PC10 is good?
11)Check +30 volt dc primary voltage on boost control board PC10
Replace PC10 ifnecessary.
I Dont know where to test specifically on PC10 for this test
12)Check 15 volt dc primary voltage on boost control board PC10 Replace PC10 if necessary.
I dont know where to test specifically on PC10 for this test

13)Check +15 volt dc buck voltage on boost control board PC10 .
If voltage is present,
stop. If voltage is not present, check resistors.
Before checking resistors, discharge and measure input capacitor voltage .
I dont know where to test for this on PC10

14)Disconnect PC10 from PC2 and check resistors R1, R2, R36, and R37 on PC2. Each
resistor should measure 75K ohms 10%. If any of the resistors are bad, replace PC2.
These resistors on the Maxstar SD are 150k ohms each. All four check out good and within tolerance.

I need specific test points/locations to questions 8, 11, 12, 13.

Again, Thank You for anyone up to the challenge. Brian