Welder not turning on - Learning

[Olles4]

Oyyy, made a mistake yesterday, R209 goes to the Source, not to the gate. It's a current sense resistor. So 1 v is the max here. As soon as the CS pin goes above 1V there is current limiting / cut off. Thinking about this, the resistance must be quite high. Higher than 1k Ohms. More like something 10k or 100k Ohms. Can you check the capacitance of C204?

Update:

Here is some photos of the main board. Im trying to remove the big heatsinks right now to see what is under them.

[CapLeaker]

Oyyy, made a mistake yesterday, R209 goes to the Source, not to the gate. It’s a current sense resistor. So 1 v is the max here. As soon as the CS pin goes above 1V there is current limiting / cut off. Thinking about this, the resistance must be quite high. Higher than 1k Ohms. More like something 10k or 100k Ohms. Can you check the capacitance of C204?

[CapLeaker]

That's the problem. Them 2 resistors I am not so sure of what there was in there, I went after the carnage trying to identify what was there first place. Some were really easy to identify, others not so. The thing here is to go through example circuits that are similar to yours and see what they used. Pull up some datasheets from the PWM from different manufacturers and compare. Sometime you know the resistor code started with a 1 and ended in a zero for example. So far R207 and R209 I haven't come up with anything too good uet.

R207 ended with xx01. So a 1001 = 1k ohm. Sounds plausible and should work.
R209 got not a clue. Cording to your schematic, it is a gate drive resistor to a different MOSFET. Knowing that it should be something less than 100 Ohm. Don’t forget there are already 22Ohms in line.

[Olles4]

Is it better to put higher or lower value resistor on R209 and R207 ? I mean which way is safer.

[CapLeaker]

It is starting to make a bit of sense now how this works. Good drawing! Here is with what I roughly came up with. I am not sure on the exact value of R209 and R207. The BYV26E is better than the 1n4937 that I guessed on D201.

example circuits show R207 as 10k Ohm… as 10R0?

[Olles4]

I need somehow to guess the values of : R209 , R208 , R207 , D203.
And replacement for : D201 , i found this diode was BYV26E

[Olles4]

Let me know please if its readable. Thank you

[Olles4]

[Olles4]

[Olles4]

[Olles4]

[CapLeaker]

Very good!

[Olles4]

i already working on the schematic i need one more day to finish it

[Olles4]

I just pulled the sales flyer for it and it has Lincoln Electric on the bottom of it. So you should be able to get a spare board as that company shouldn't be bankrupt.
Try these guys in Slovakia :
AIR LIQUIDE WELDING CENTRAL EUROPE S.R.O.
Hlohovecká 6 - 951 41 NITRA - LUŽIANKY
Tel.: +421 37 692 4610 - Fax: +421 37 651 28 04

https://www.wecs-ltd.co.uk/wp-conten...erlikon_en.pdf

already tried but its closed and there is other company
Air Liquide Welding Ltd. - Google Maps

[CapLeaker]

The worst thing is the company went bankrupt and there is no more spare parts.

I just pulled the sales flyer for it and it has Lincoln Electric on the bottom of it. So you should be able to get a spare board as that company shouldn't be bankrupt.
Try these guys in Slovakia :
AIR LIQUIDE WELDING CENTRAL EUROPE S.R.O.
Hlohovecká 6 - 951 41 NITRA - LUŽIANKY
Tel.: +421 37 692 4610 - Fax: +421 37 651 28 04

https://www.wecs-ltd.co.uk/wp-conten...erlikon_en.pdf

[CapLeaker]

The gate drive resistor is usually something between 0 and 100ohm, the gate drive diode is probably something similar as an RB160L60. The diodes trough hole I'd put something 1A, 600V or better ultra fast in there. The gate resistor and the diode are there to slow the Mosfet down and prevent ringing.
As for R209, I am not sure where it goes to what pin in the IC.
Drawing a supporting schematic would simplify things for sure.

[Olles4]

almost forgot the mosfet is K3878

[Olles4]

I removed the heat sink and the mosfet so u can see more and also tried to clear the gunk. I can write a diagram if you want me to.
Note: D201 is also blown and from bottom side R209 too.

[CapLeaker]

Pin 6 is VCC so that bigger resistor can’t be that high in value. Pin 7 is the destroyed gate drive with the smaller resistor and diode. The diode isn’t that critical but the gate drive resistor doesn’t have to be bang on, but should be as close as we can get it.
What was the mosfet? Upload a straight shot picture of the board from top.

[Olles4]

I guess you got 2 choices.
A: Replace the board as a whole
B: Maybe you are lucky and find the datasheet from that 8pin DIP IC (gate drive) and see what the example circuit has to offer.

Chances are you going to need that IC anyway, since the Mosfet blew and shorted to the gate drive.

Is there a possibility to recreate the board ?