Power Mig 255 PC Board

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I bought a broken Power Mig 255 last night. It was cheap and has a new gun on it so I figured it was worth the gamble.When plugged in, the transformer hums but it doesn't do anything else.I've done a little testing with a multi-meter to rule out the basic stuff, although that's not something I'm great at. The welder was at a Lincoln repair facility and they told the previous owner that the PC board is bad. The weird thing is, someone put a PowerMig 255C board in this welder. The board is dated August of 2017. The guy I bought the welder from said it did function with this board in it as one point, however he didn't seem to have 100% confidence when he said that. Comparing the wiring diagram between the G3521-1 (correct 255 board) and the G4824-3G1 (255C board currently in machine), they appear to be very similar.Unlike the correct board, the 255C board is potted with clear epoxy in a back plastic case. I'm tempted to cut it out so I can inspect the back side of the board for burned up traces.I'm thinking the best course of action is to do a little more diagnosis of basic parts and then just order the correct board.Does that sound like the best approach?And my second question, does anyone have a parts Power Mig 255 that they'd sell me the board from? I'd hate to buy a brand new board and instantly fry it if something else is wrong with this welder.
Reply:First what is the code number of the welder, with that we can see if you have a 255 or a 255C then we will know which pcb is the correct one.the 255c pcb cost a lot more than the 255 pcb.Find the diagram in the welder. Find the main transformer try to measure the voltage on all the secondary coils. then find the D2 diode and test it. make sure it is not open or shorted. other things to look at are the gas valve and make sure it is not open or shorted. don't have either in the shop right now so not sure what the difference is.But you can call Lincoln tech support and ask them. and if the 255c pcb could have worked in your welder and could it have damaged anything.As long as you ask good questions and show you have the knowledge to safely test the welder they will work with to find figure out what else might be bad and if when you buy the right pcb will it get damaged. They will not help with PCB repairs so don't ask. they will cut you off. You can go to lincoln web site and under the support tab find the parts button.open it and select the guest tab. this will take you to the service navigator.enter you code number and it will take you to the correct parts list for your machine and a lot of other information. parts order and pricing is disabled.
Reply:Appreciate the suggestions! I'll check those parts today.This is the first time I've ever torn into a welder. It's a good learning experience and I look forward to welding with this thing eventually (hopefully).The code is 10990. The G3521-1 part number I listed is the one Lincoln calls for. I talked to Lincoln tech support yesterday and ran the scenario by the guy. He suggested putting in the correct board, didn't have much input about the 255C board being able to operate the welder or if it could have damaged anything.I tested the D1 diode last night and believe it is bad. I get the same value with the multi-meter leads in either direction, so the diode is open, right? It's on a large aluminum heat sink and some of the other connections on that heat sink look a little crispy, like they got hot or arced out at one point.A friend of mine sent me a pretty detailed Lincoln troubleshooting guide for this specific machine so I'm going to follow that today.
Reply:

Originally Posted by Shwoody

Appreciate the suggestions! I'll check those parts today.This is the first time I've ever torn into a welder. It's a good learning experience and I look forward to welding with this thing eventually (hopefully).The code is 10990. The G3521-1 part number I listed is the one Lincoln calls for. I talked to Lincoln tech support yesterday and ran the scenario by the guy. He suggested putting in the correct board, didn't have much input about the 255C board being able to operate the welder or if it could have damaged anything.I tested the D1 diode last night and believe it is bad. I get the same value with the multi-meter leads in either direction, so the diode is open, right? It's on a large aluminum heat sink and some of the other connections on that heat sink look a little crispy, like they got hot or arced out at one point.A friend of mine sent me a pretty detailed Lincoln troubleshooting guide for this specific machine so I'm going to follow that today.
Reply:Well I'm gonna have to throw in the towel on this one unfortunately

Looks like someone removed the snubber board and did some wire rerouting. I'd imagine that's a pretty critical component, right? A new snubber board is $110, plus the time of having to undo someone's wiring job, plus the cost of a new $700 PC board. Just not worth it for a 17 year old welder that may have other issues for all I know.
Reply:It looks like the Power Mig 255C doesn't use a snubber board. I can only assume someone had that 255C board lying around so they decided to do some adapting. Can't see any other reason to replace the correct board with a more expensive one.I may still fool around with this thing.
Reply:post a picture of what you think is the D1 diode.D1 diode is about 1 inch square block with 4 connections. It is a bridge diode assembly with 4 diodes. only 2 are used. An ohmmeter may read OL both directions.will depend on the meter and what range you selected. Diode test mode is best.If you measure the right two wires it will read a short circuit. Because you are reading the transformer coil.Set down with the diagram and colored pencils. Trace out each circuit and mark up your diagram showing circuit is still there and correct or missing or changed.Then if you decide to spend the money on the pcbs and repair it. You will be ready to correct the changes in the wiring. Might have to buy some plugs and sockets. if harness is missing or damaged. Can be purchased from Lincoln or an electronic supply house. If you can find someone local that has one and will let you take covers off and compare will save a lot of time figuring what is missing or changed.
Reply:Shwoody,Thanks for buying that. I looked for it the next morning, and it was gone. Hard to resist at that price.Have you checked the companies that rebuild welder boards?Innovatcorp.com shows $470 to repair the board I looked up. It is a G2803-1. When I searched for the mainboard that's the number that came up several times. Some of the companies may have inventory of the board you need. I hope you get it working.Steve
Reply:

Originally Posted by ccawgc

post a picture of what you think is the D1 diode.D1 diode is about 1 inch square block with 4 connections. It is a bridge diode assembly with 4 diodes. only 2 are used. An ohmmeter may read OL both directions.will depend on the meter and what range you selected. Diode test mode is best.If you measure the right two wires it will read a short circuit. Because you are reading the transformer coil.Set down with the diagram and colored pencils. Trace out each circuit and mark up your diagram showing circuit is still there and correct or missing or changed.Then if you decide to spend the money on the pcbs and repair it. You will be ready to correct the changes in the wiring. Might have to buy some plugs and sockets. if harness is missing or damaged. Can be purchased from Lincoln or an electronic supply house. If you can find someone local that has one and will let you take covers off and compare will save a lot of time figuring what is missing or changed.
Reply:Innovat has the G3521-1 listed for $330.Steve