DC-600 Firing Board Needed

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I've got a DC-600 with a burned out firing board. Anyone have one of these laying around? Used but working condition is fine.I'm working on getting the correct board part no. and code number off the machine. Thanks.Eric
Reply:Part number is on the pc board. It starts with a GYou need to find the part number on the pcb. you need the dash number.The parts book gives the first part of the number. G1111-(). When buying a new pcb we have to enter the old part number into the price book and let the price book select the correct replacement part.I am going the guess Your pcb has lots of small resistors in a row that have burned up.That design did not work well. They replaced it with a pcb with one that has large white resisters on it. Before you install the replacement pcb. Take a ohm reading on each gate lead pair. white to red wire. There are six pairs. makes sure they all read the same, around 30 ohms. Use standard ohm meter setting. check both ways. They all should read real close.A shorted gate could be what burned up the pcb. But some times they just die.
Reply:Originally Posted by ccawgcPart number is on the pc board. It starts with a GYou need to find the part number on the pcb. you need the dash number.The parts book gives the first part of the number. G1111-(). When buying a new pcb we have to enter the old part number into the price book and let the price book select the correct replacement part.I am going the guess Your pcb has lots of small resistors in a row that have burned up.That design did not work well. They replaced it with a pcb with one that has large white resisters on it. Before you install the replacement pcb. Take a ohm reading on each gate lead pair. white to red wire. There are six pairs. makes sure they all read the same, around 30 ohms. Use standard ohm meter setting. check both ways. They all should read real close.A shorted gate could be what burned up the pcb. But some times they just die.
Reply:The SCRs can be replaced one at a time or in pairs. Do the SCR test firstThe complete assembly has to be removed from the welder and placed on the bench.The SCRs are held in the heat sinks by a clamp.There is a spring that breaks once and a while. so you will need to look inside the white box spring holder. It is a flat spring.The secret to replacing and not have problems Is clean, clean and clean all connections that are removed. while having it out. you will want to clean and reset all the SCRs. One pair at a time. Heat sink grease on the SCRs and Aluminum connection grease on all other connections. Use a very thin coat. When putting SCRs back together the pressure must be the same on both clamp bolts.1 turn at a time until clamp touches then 1/4 turn until tight. do not over tighten. just tight enough so you can't move the heat sink pieces. See attached page. It gives one way to test SCRs. You will need to disconnect at least 2 transformer connections to isolate the SCR from parallel circuits. Attached ImagesSCR test.pdf (72.2 KB, 95 views)
Reply:Do not buy the firing pcb unless you can get the part number off the old pcb. The older machines used a square plug and the newer machines used a rectangle plug with two rows of contacts. With the adapter harness kit the newer pc board will work in the older machine. But the old pcb will not work at all in the newer machine. Once you have the part number  a higher dash number will always replace the lower dash number. Post the part numbers and I can double check and see if they are correct replacements.But we have to start with the one in the machine now.
Reply:Originally Posted by ccawgcDo not buy the firing pcb unless you can get the part number off the old pcb. The older machines used a square plug and the newer machines used a rectangle plug with two rows of contacts. With the adapter harness kit the newer pc board will work in the older machine. But the old pcb will not work at all in the newer machine. Once you have the part number  a higher dash number will always replace the lower dash number. Post the part numbers and I can double check and see if they are correct replacements.But we have to start with the one in the machine now.
Reply:Any chance of getting the owner to take clear digital pics of the board? That removes any need for verbal descriptions.
Reply:I will second the picture. Have him send you one and the post it here.York does a good job repairing pc boards. But not all pc boards are repaired on the first try.It some times takes a couple of tries. Because the pcb has burnt resistors. Tell him you need a good picture of the front and back to sent to the repair place. To find out if it is repairable or if a new one is the only way to go.The part number is along the edge of the pcb.
Reply:Well, still trying to get the pics but I did get the number off the board. Its a G-1486-5. I do have one pic that came from the guys cell phone I think. Not much detail and its just part of the board.I'm thinking I'll go the York route since they have a decent rep. here.Here's the photo of the board (just a little smoky): Attached Images
Reply:Send that picture to York and see what they say.Before you put a firing pcb in this welder you had better use the test sheet I posted and test all 6 SCRs. Two of them may have shorted gates. I see two gate drive transistors have burned up. Hope this machine is not to far away because you are going to have to do some tests. You don't want a new or repaired pcb to go up in smoke on the first power up. The large white resistors are normal.  Going to look hard at the pcb and with my books see if I can tell you a little more about the failure.
Reply:All the burnt parts appear to be in the firing circuit for SCR 5 and 6. SCR 5 most likely has a bad gate. One of the burnt( blown off the pcb center bottom) resistors is is series with the gate to SCR 5.You are going to need a new or repaired pcb and at least SCR5, but you will want to replace SCR 6 also. You also can Contact Lincoln send them your picture are see what they think.I hope the damage is contained to the firing pcb and did no back feed into the control pcb.Check R48 and D33 on the firing pcb and see if they got damaged. Attached Imagespcb.pdf (79.1 KB, 83 views)
Reply:page two.I was going to post the diagram of the pcb, but it's to big. If you want it, send me your E-mail by Private message.
Reply:Thanks again for the information and suggestions. Could you recommend a decent source for the SCRs?Eric
Reply:I sent the picture to Lincoln factory tech support. The response I got back was you may have one of two problems that caused the pcb to fry. We either have a bad SCR or a shorted gate wire in the harness to that SCR. I recommend You check the welder out before you order parts. The Lincoln part number for the SRC is M12283-5 Can be ordered from any body who sells Lincoln parts and machines. You can try looking on the SCR for a different number that a electronics house could sell you but I think the above number is the only one on it.
Reply:Final Update-Well, the guy who bought this welder had his Lincoln guy check the SCRs and look the firing board over. Evidently the board is charred all the way through so it must be replaced. Two of six SCRs are blown and the tech has recommended to the buyer that all the SCRs be replaced.I was willing to pick up the cost of the firing board repair but I'm not going to dump this much money into it. So, its coming back to me for a refund (which is, in my opinion the only fair way to handle it) and I'll try and figure out what to do next.Any ideas what I might be able to get for a DC-600 that has had the firing board and all SCR's replaced? The parts alone are going to be close to $1000.00. I can do the work replacing them myself and hopefully find someone I know with 3 Ph. to test it afterwards.Or, I could just scrap it for next to nothing. I don't have anything invested in the machine right now except some time.At any rate, thank you very much for your continued interest and assistance with this thread.Eric
Reply:The best repair is replace all 6 but if both of the bad ones are on the same phase you should be able to replace just those two. you should at least replace them in pairs. If the two SCRs on is two different phases then you should replace 4. When one of these die they can put a lot of stress on the other SCR and weaken it. You never know if or when the other SCR will fail. The SCRs from Lincoln List for around $115 and the G1587-5 pcb Lists for around $330. Prices will vary do to mark ups and shipping.So for a little over $500 and about 3 hours labor you might be able to fix it.But you will want to test all the SCRs for your self and see which ones are bad.Use the method I posted earlier. There is a trick to replacing the SCRs so if you decide to do it contact me by private message And then I will tell you what to do.You can test all the SCRs in the welder. All you need to do is remove two of the three wire coming from the transformer that connect to the SCR assembly. and may be pull J1 and J3 from the control pcb. When you get ready to replace the SCRs. the complete SCR and heatsink assembly will need to be removed and placed on a work bench. Make sure you mark all wire before disconnecting them. When you get the new SCRs message me and I will give you the rest of the steps. Do not try to disassemble the heat sink until you contact me.Post #4
Reply:Thanks again ccawgc. Got the welder back yesterday. I'll be working on the SCR testing and visual inspection of the control board. I'll definitely PM you before I remove the SCR assy. Eric