Hi all, still doing sone tests, will be posting my findings on the weekend,

Hello Wandering 909
The next time i have the board out, i will try to get the part number on D72, the board is covered with this varnish, so i need to scrape it off maybe i'll be able to see the number.
I have to redo all the test in the Esab repair manual, then i will pull it out. Probably on the weekend.
I will also be posting my results.
Q6-IGBT-STGW60V60DF-i have replaced it for a new one, i was sure it was the problem, since it leads to Q26, no joy!

 

well dang, i didn't know there would be legible markings under the varnish. here is a pic of Q26. yes, please send a pic of D72 when you get a chance

 

I'm not sure if you have Q26 part fixed but here is some info on it. it's a 60ZG

https://www.onsemi.com/pdf/datasheet/nddl01n60z-d.pdf

 

Super, that'sexactly the information i wanted, i will send you a picture of D72 this week end
Thanks

 

hope you get it fixed

 

hope you get it fixed

Thanks, i hope .
So here is D72 on my board

 

BYV25FD-600 Enhanced ultrafast power diode

 

hell yeah!!!! hopefully we can get these pos welders to go again. thanks!

 

I'm not sure if you have Q26 part fixed but here is some info on it. it's a 60ZG

https://www.onsemi.com/pdf/datasheet/nddl01n60z-d.pdf

Thanks. I think its more likely to be an NDD03N60ZT4G (hence the 3N as well as 60ZG, T4 being the DPAK case variant.)

But there's likely to be other parts faulty on board. These things don't fail for no reason.

 

Thanks. I think its more likely to be an NDD03N60ZT4G (hence the 3N as well as 60ZG, T4 being the DPAK case variant.)

But there's likely to be other parts faulty on board. These things don't fail for no reason.

Hello Irving
NDD03N60ZT4G Obsolete
This product is no longer manufactured.

i was thinking maybe
FDD5N60NZTM
MOSFET N-CH 600V 4A DPAK

 

i was thinking maybe
FDD5N60NZTM
MOSFET N-CH 600V 4A DPAK

I'd say that's a reasonable alternate. Switching times are quoted as a bit slower but at a higher gate resistance (25 ohm v 5ohm). For this application I don't think thats an issue.

 

Well i would be very surprised if it powers up. As you say, there is most probably something else that blew.
I removed and checked the 4 500v470ufm capacitors, they are good. Unplugged all wire to the BR1 and BR2 rectifiers, checked all good. Replaced IGBT to Q6, still no change. Maybe another IGBT ? 1 of the 2 10k resistors gets a little warmer or hot when i leave the power on, 50 - 60 deg. cel. vs 20 for the other. Led 44 does not flash as indicated in the manual. Hoping to find the trouble soon. Thanks for the help

 

1 of the 2 10k resistors gets a little warmer or hot when i leave the power on, 50 - 60 deg. cel. vs 20 for the other.

That suggests one of them is faulty, possibly open circuit (the cold one) - they should be the same.

 

Hello, so i removed the 2 10k resitors and put 2 new ones, both the old ones are good i think, test reading = 9800 and 9810 but i may have broken the trace, see pics, my bad, i must be more careful.
Now they are at same temperature - + 1 deg.
re NDD03N60ZT4G is Obsolete and no longer manufactured.
3 AVAILABLE SUBSTITUTES:
https://www.digikey.ca/en/cross-reference?search=NDD03N60ZT4G
What do you think is best ?