Resistance Welder SCR Controls

[TimWilborne 108]

What started out as a joke by Gravitar HERE about a Resistance Welding Forum appears to be gaining speed so I figured I would go ahead and post my last (I hope) problem with my Flash Welder rebuild. Three fine gentlemen of this forum have been helping me with this through PMs. Any of you please correct me if I say something wrong or add in anything I miss. This flash welder was built in 1971 and the years have not been good to it at times. The main two problems left is it's snubber circuit has been removed at some time and it's has an SCR firing board from a company that no longer exist, First the Snubber Circuit. Without this the potential across the SCR will not drop to zero. There was a contactor added to switch along with the SCR to stop this problem. I would like to add the snubber circuit back. Does anyone know how to size it? My other dilemma is my SCR firing board. It works fine but the problem is the company the made it has fallen off of the face of the earth. Here I have two options. Find another SCR firing board or replicate my existing board for a spare. I have searched for a board but am having trouble finding one. Let's discuss that option before we get to the alternative of replicating the board since I am looking for information about the flash welder parts and not the ethics of replicating the board YET. I would be grateful for any help that could be given but you will have to be patient, I don't know a lot of the correct terminology when it comes to these machines Thanks TW Below are some schematics and picture that have been passed around in PMs. This is an overall of the of the SCR panel. The only thing to note here is the X layout of the copper that from what I understand is on most of the old Ignitron units This is a schematic of a replacement SCR for the Ignitron. While it is not ours, it is identical This is a picture of the current SCR. The part number on the pucks is a GPS*DCR1007 SF2222-25 9528 The MOV is a Z550PA80C CKE 9628 Here is the basic SCR Circuit Original SCR Circuit. The only thing that is left is the transformers. From what I understand the load resistor is the snubber circuit. Is this correct? Specifications of the two 200kva transformers

[Ron_Smith 13]

Good job... first question and it's a wopper I've searched and couldn't find anything useful as far as sizing the snubber circuit. Wasn't it part of the firing board originally? I've got a couple of boards similar to what you have pictured. I'll poke around and see what I can find out. Do you have a vendor to talk with? I've used TJ Snow before and they were always very helpful.

[TimWilborne 108]

I will look them up. Thanks again TW

[Sleepy Wombat 27]

Wow, another thread resurrected from the dead, seven years later... thats got to be a record.... BTW Tim, did you find your answer on Google ? if not remember to try Yahoo... while your at it try Alta Vista and Bing and ........

[TimWilborne 108]

7 years ago or today, you aren't finding these answers on Google! I thought I was back in a nightmare when I saw this thread resurrected.