SMD identification Magic Wave 2600 BSP26

[ApoSensei]

Well wouldn't it be funny if my last message bit me
Yesterday I was working and had the welder powered on but was not welding. I had a part that needed turning on the big lathe. After I finished turning my part I noticed that the welder was in stick mode but there was no voltage again. I checked the fuse on the top board and it was not blown. However on the TTS8 board I noticed that some components got really hot. I took it apart and other than the burned diodes every other component seems to be working. I checked the mosfets and diodes on the heatsinks all are ok. I couldn't find any short on the board. The igbt modules and the diodes behind the board all measure fine without shorts.
Does anybody have an idea what could be wrong ? Again I was not welding when it occurred. It was idling in stick mode.
Could it be that the lathe on power up might have messes up something on the welder ? It is not a small machine a 5kW 3 phase lathe that is hooked up to the same circuit as the welder.

 

[Jan-DIY]

The Igbt modules are not igbt.
These are darlington transistors.

Mains power supply is not the reason for this.

Looking really bad anyway.

 

[ApoSensei]

Yeah, the pads of the diodes are done. Fortunately they are just in series so I can repair the traces with wires or something. I can't seem to find any faulty component on the board. Unfortunately I am not able to test the voltage regulator (L4977A) but other than that everything else seems to be normal. The diodes on the right side are also checked and are working.
Is it possible for the Darlington modules to have such a failure ? I mean I know of machines that break when they are turned on or during welding but never when a machine is idling

 

[ApoSensei]

I might also add that after replacing the resistor and so on on the primary board and the fuse für the 30V line the welder was working perfectly. Tig and stick both in Ac and dc were no problem at all through all amp ranges. That's why I am so confused about it

 

[Jan-DIY]

I got some faults in the past in these section but the voltage regulators died.
And I also got machines which died when idling.
The TTS8a is a very complex module anyway.

As I can see AC and DC- lid in one picture.
Was it disappeared after you changed the resistor?

 

[ApoSensei]

i Hope you mean the LED's on the front panel. There was a defective resistor that I changed. After that the front panel worked without issue. I would like to write in German for better understanding but some might get upset

 

[Jan-DIY]

You can write me via pm.

 

[ApoSensei]

Back again, I replaced the diodes and both voltage regulators on the TTS8 Board in case they went bad. The big transistor at enorm easy to measure but according to the datasheet I could measure the resistors and a diode which measured fine on both. The diodes on the right side also measured fine. Today I installed everything back and turned it on. At first no voltage after a couple seconds voltage started to rise but was fluctuating between 40-55 V. All leds wer lit but after a couple seconds the 30V fuse which I replaced prior burned out again. I also checked some resistors and the optocopplers for their diode no findings there. Anybody an idea what I could check else ? A very strange fault since the machine was welding both in tig and stick fine