Inverter Welder Repair

[WelderCrafts]

Hello I'm new on this site need some help with an inverter welder which I am trying to fix.
I have a repair manual for it but can't seem to find a transformer replacement for it.
Was wondering if anyone could advise me on what transformer I would need judging from the schematic that I've attached.
The Transformer is marked TR2 (M26127 C4209).
 Thanks in advance.

[xavier60]

It's more likely that the SMPS IC has failed. Check all of the diodes first.
Be certain that the large capacitors are fully discharged before working on it.

[WelderCrafts]

Hiya thanks for the reply I checked all the diodes and changed out the fried ones still didn't work so I pulled out the transformer and on the primary side it has no reading.
I even tested it with the power on checked to see if there was any voltage coming from the output side of the transformer nothing at all

[xavier60]

I did a search on "Welder Auxiliary Power Transformer" and found many. But one has to be matched to the original with high certainty.

[shakalnokturn]

I even tested it with the power on checked to see if there was any voltage coming from the output side of the transformer nothing at all

Does that mean you ran a couple of wires and a mains plug to the primary?

[xavier60]

Hiya thanks for the reply I checked all the diodes and changed out the fried ones still didn't work so I pulled out the transformer and on the primary side it has no reading.
I even tested it with the power on checked to see if there was any voltage coming from the output side of the transformer nothing at all

It seems really odd that there would be faulty diodes and open primary.
Which diodes were faulty and in which way did they fail?

[George Edmonds]

Hi

From the looks of it this is the low voltage power supply, can you show the entire power supply drawing.

It is unusual for SMPSU transformers to go open circuit they usually fail with shorted turns.

George G6HIG   

[WelderCrafts]

I did the testing while the transformer was still on the board 

[WelderCrafts]

I attached the pdf of the welder mines the one with the 3 big capacitors.
Might have to scroll down abit.
Appreciate all your help

[WelderCrafts]

Hiya thanks for the reply I checked all the diodes and changed out the fried ones still didn't work so I pulled out the transformer and on the primary side it has no reading.
I even tested it with the power on checked to see if there was any voltage coming from the output side of the transformer nothing at all

It seems really odd that there would be faulty diodes and open primary.
Which diodes were faulty and in which way did they fail?

I highlighted the diodes that failed  and the one capacitor.
They are all in line with viper IC.
Only problem is that I'm not too sure on how to test ICs  so I have no clue whether it's fried or not.

[xavier60]

Damage to those parts should mean damage to others like T2 also.
Seems the original cause should be IC2 having broken down, drawing large fault current through the primary, also spiking components connected to it.
But usually these small SMPS IC blow their tops in an obvious way.
You can check for pins that are short to ground although they can just as likely to be open.
One certainty  will be from checking for the presence of the internal MOSFET's body diode.

[WelderCrafts]

Damage to those parts should mean damage to others like T2 also.
Seems the original cause should be IC having broken down, drawing large fault current through the primary, also spiking components connected to it.
But usually these small SMPS IC blow their tops in an obvious way.
You can check for pins that are short to ground although they can just as likely to be open.
One certainty  will be from checking for the present of the internal MOSFET's body diode.

.

I changed out all the mosfets as I thought that was the problem at first but after testing still didn't work then I tested the viper circuit looked like it wasn't getting any power.
upon examining the transformer I noticed a a burn mark on the bottom side which led me to think it was defective I removed it from the board and did a resistance test and indeed it is defective.
Going to try find a replacement and change out the viper IC and see how it goes from there.
Really appreciate all the help
Thank you so much