Sunday, December 20, 2009



Please note that the following components were used for version 1 and are not necessary to install for version 2. 
Q1, Q2, Q3,
D6, D7
R4, R8, R9, R10, R12, R13, R27


  1. I have browsed the schematic for some time. I have not found the many mosfets that are seen on the heat sink below the pcb. Nor have I found the power resistors in the schematic.

    There was also a mention of a contactor. Where is that found in the schematic?

  2. Darrell, you have no idea how many hours, days and months I have spent designing and building this welder and there's a lot more, that I have to do to get all schematics and paper work done. If you send me a couple of hundred bucks though... I will stop what I'm doing and work throughout every night to get it done just for you....How about that??
    Go read below the schematic page again to get the answer about the contactor.

  3. Hi Fritz, Thanks for the BOM. I see you made everything fit nicely with the space you had to work with. It's lookink good, cant wait to get one started. I noticed that you use copper bars from the cap and the board. Does it make significant difference than using a low gauge cable? I was planning on using 4 gauge cable or maybe lower. Thanks.

  4. That was a ton of work! Great to see a BOM Fritz! -Mike

  5. Damian, you can use cable instead of copper bars. The size of your cable will make a big difference though and you want to make it as big as you can. I used a 2 gauge on mine.

  6. Thanks for your responds Frits. I'll try the copper bar first. If I have problems I'll use 2 or zero guage.

  7. Recently I bought some 2907 mosfets from Thailand.
    The contact is on ebay, but I bought directly from him at a cheaper price.
    I am using these mosfets for another project, but will get some more for a capacitor discharge welder, I have a need for one of these machines.

  8. You can get the same mosfets from Hong Kong for $3.50....$2.00 shipping

  9. Hi fritz:
    I'm building the welder and I do not find the value of D9 in the control PCB.
    Can you tell me what it is?

  10. Juan, if you look in the manual page3 #8 it says clearly that D9 has to be jumped. At the time of design I used D9 as a place holder for a separate circuit to disconnect the capacitor from the charging circuit when a problem occurs. I never built that circuit so just Jump D9.


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