SMD identification Magic Wave 2600 BSP26

[ApoSensei]

Hello guys,
It's my first time posting here and English is not my native language so please go easy on me.
I bought a defective Magic Wave 2600 the other day.
At first startup the machine seemed to turn on normally and the coolant pump squirted a bit before stopping (startup sequence i guess). The display operated however the ac mode light was always on, a bit dim but on. If i tried welding i had zero output, nothing. I took apart the machine and noticed that the resistors on the BSP26 board got quite hot some time. I found an old thread here where a user pointed out that these resistor often get bad.
After i changed them the display now shows UP as an error and locks up the display. I am not sure how the machine is supposed to operate but on the BSP26 board there is only one red led working (far left one, 15V indicator perhaps). The other leds for over-/undervoltage don't seem to light up. I was able to find a broken SMD transistor which i wanted to replace. Unfortunately I can't read off the part code that is written on it. Does anybody has the ability to check or knows what kind of transistor i need ?
Some other facts about the machine are that the input rectifier seems to be working and outputs ~580V on the capacitors. Also the diodes on the heatsink seem to be just fine eventhough I measured a voltage drop of about 0,4V on a couple of them and ~0,33V on the rest.
I would be thankful if somebody could help me out.

 

[Kram]

It may be the pictures and lighting but I can see a few components that look blown including two IGBT drivers, so posibly the IGBT's are blown aswell?

 

[ApoSensei]

The igbt's are what I called the diodes on the heatsink they all read fine and are not shorted. As for the other components it is just the coating that bubbled up after applying in the factory I guess. I also checked the optocupplers which seemed to work. The only issue i could find was that one blown transistor. If it responsible for the non working leds, i don't know

 

[ApoSensei]

I think I got it. If anyone in the future wants to know it seems to be a transistor also used on other places on the board. It either says "5B" or "513"

 

[pedrobedro]

Google 5B comes up with bipolar transistors. Looks like the part in the picture.

 

[Martin-Sy]

Plenty of on-line reference sources for SMD device codes. eg

https://www.sos.sk/pdf/SMD_Catalog.pdf

but it is a bit of a minefield!

Which for 5B says either BC847-25 or possibly MMBT4123.
In both cases NPN silicon transistor. I'd stick a BC847-25 in if it were me.

 

[Jan-DIY]

BC807-25

 

[ApoSensei]

I desoldered the ok looking transistor and testet it in a tester. It came back as a pnp transistor. I found a pnp on a different board swapped it and tried turning the machine on. The same transistor blew out again

 

[ApoSensei]

I don't know if it is the right place to post it here but in my welder there was a circuit Diagramm which I did not find online. So if anybody has trouble putting the cables to where they belong they can take the Diagramm for help

 

[Martin-Sy]

BC807-25

Quite right, I really must get some new glasses!

 

[Dragnet]

I can't make out that diagram enough to see what's what. If it's blowing, you must have a shorted path somewhere to make the transistor pass too much current. Trace the diagram from that transistor, and check resistances for a short along the current path after the transistor. You could also look up the datasheet for the IC next to the transistor and see if it has an example circuit which will help you understand what's going on around there. Sometimes manufacturers take the suggested circuits wholesale and simply duplicate them in their machines, making things a lot easier to track down.

 

[ApoSensei]

That's what I wanted to do, just didn't have time to dig deeper. As far as I understand the BSP26 boards gets 15V from the board on top of it. Since the 15V led on the BSP26 is lighting up I assume that part is working. Probably some sort of comparator circuit that checks/controls the input and the rectified voltage.
As for the Diagramm, that's the best my scanner is capable of. There is not much written only which connector goes to which board and a couple voltages the cables are carrying i.e. 2x +15V and 2x GND for the connector between BSP26 and the board ontop.
Offtopic but that coating on the boards smells disgusting when soldering

 

[ApoSensei]

So i put in another transistor to check if I could reproduce the behavior from last time. Again at startup something from that area let the magic smoke out. However this time the machine did not jump into the UP error but let me turn the knobs for amperage control. But still no power when trying to weld. I took a couple of pictures while the machine was on. Can anybody check if the leds that are supposed to be on are indeed on ? The panel shows that the ac sign is always on, what I said in the beginning. I don't know if the machine checks the voltage after the secondary rectifiers but could it be that something in the secondary side is not working and thus not providing the voltage ?
I also don't know what could be wrong with the panel I put on a torch and it recognizes the torch trigger when pressed

 

[r3ks10]

+30V ?

 

[ApoSensei]

+30V ?

View attachment 484092

That one appears to be not working, do the 30V come from the TTS8A board ?

 

[r3ks10]

Nie, z UTI2A. Sprawdź bezpiecznik przy LED.

 

[ApoSensei]

Got it, will check probably tomorrow. On the BPS26 I found a shorted Zenerdiode on the Relais which I changed (original Uz=0,9V, changed for a 1V since inhaftiert one on hand). On startup something else on the BPS26 gave out the magic smoke but I was not fast enough to identify the part

 

[ApoSensei]

After changing the blown fuse for the 30V rail the machine started up and build up voltage. The screen said around ~55V in stock function. When I started to weld the machine jumped to the error U-P after a couple of seconds back to normal behavior. This continued until I lowered the amperage to around 50 A where it almost seemed like it was welding fine but smoke was coming out of the BPS26 board. Upon closer inspection the big 10 Ohm resistors where smoking. I guess I have a problem with the Relais circuit which does not close the Relais and thus overworks the resistors.

 

[r3ks10]

most likely a shorted diode damaged the transistor

 

[ApoSensei]

The transistor was shorted again since I tested the board without checking/changing the Zenerdiode on the Relais. I will have to test tomorrow if everything works now. There is still the issue with the display where the ac light is always on. The settings work flawlessly so I assume either a transistor that is stuck on or one of the Chips got damaged. Will have to check when I have time though. All in all a pretty good machine with minor defects for 350€