Transformer marking: T21150W25

[stryker]

Hi,

I have a power supply with a transformer that appears to have an internal short.  There's a sticker on the top that says T21150W25 but that's not coming up as a part at any of the usual suspects, nor more broadly in a google search.  I'm hoping it gives a hint to its characteristics so I can find a swap-in replacement.  It's in a 28V power supply for a Waeco fridge.  Waeco's distributor wasn't able to provide a schematic so hoping this code is a hint.  Does it look like a manufacturer code you recognise?

Thanks
Geoff

[SeanB]

Picture of the transformer will help as well. Is it a small potted transformer soldered to the board, running off the mains direct, or part of a SMPS on the board.

[stryker]

Here's a picture of the transformer.  Hope this helps.

I've borrowed a working example of the power supply and the resistance between the 4 terminals on the transformer are hugely different.  It also means if we can't identify this from the marking I'll be able to pop the working one off the PCB and test the ratio that way.

[SeanB]

99 percent likely the transformer is fine, but the SMPS controller to the right ( in the pic) has a shorted power transistor, a blown SMPS controller IC, 2 or more failed resistors on the board and at least 2 failed electrolytic capacitors, along with a blown fuse or fusible resistor and a shorted bridge rectifier diode.

[stryker]

Thanks for the tip.  I have replaced one electrolytic cap that was looking second hand.  Will revisit the high voltage side closer as I can compare with the working one. 

[Dci]

Hi everyone...same power supply same transformer same problem....did you manage to fix it?

[stryker]

Hi everyone...same power supply same transformer same problem....did you manage to fix it?

It got pushed aside this week for other projects.  Hoping to get some time on it over the weekend.  For the record it's a Waeco Mobitronic MPS-50A, which also goes by the brand name Waeco Coolpower it seems.

[stryker]

As per the tips poste by @SeanB,

• Removed the heatsink, tested all the resistors and they measure correctly. 
• Removed the large electrolytic I'd not yet replaced and it tests fine also on an LC meter. 
• There was some brown sticky dust under a polyester 22nF capacitor (visible to the left of the power MOSFET in front of the transformer in the attached image) and it's measuring only 35pF.  I don't have anything rated higher than 100V in the parts bin so will have to get one of those. 
• IRFPC50 MOSFET is shorted out
• KBL406G bridge rectifier is also shorted

So thanks @SeanB most of what you predicted came to be true.  I have some parts to source and I'll let you know how I go.

Cheers, Geoff

[stryker]

Sorry 'bout the long break between updates.  I finally got the parts today, and can confirm that's sorted it.

Thanks again @SeanB.

[SeanB]

Hopefully you replaced that capacitor with a class X2 rated one, as it needs a pulse rating to survive long term. Ordinary polyester film capacitors will not last long there, as the high current spikes as the main transistor turns off has to be absorbed by them, and then dumped as heat in the resistor during the next switch cycle. 630V rated ones are probably the only ones that will survive as they use a thicker foil and film.

[ELEKTRO1991]

Please...  one Photo   by R18 - komponent     ...   Unfortunately, it burned down.

[stryker]

Please...  one Photo   by R18 - komponent     ...   Unfortunately, it burned down.

Sorry I don't normally have these about, and I know this question was asked a long time ago - but my brother has just dropped both his back to me to repair after they've both been caught out in the rain again.
In case it helps anyone else, for reference R18 is 510 Ohms.
Geoff

[foggs]

Do you happen to have a picture of the R13 resistor?  It's on the same side as the big Cap.
Mine is blown and trying to work out the colours/ohms.
thanks

[stryker]

You're in luck @foggs. If nobody else has one handy, my brother has two of these failed that I'll have here for repairs again soon.

[stryker]

Hi @foggs

R13 is 1k; The board I'm reading from is marked PC21150 Rev 1.6



Cheers! Geoff

[foggs]

Too good!
Thanks so much Geoff, very appreciated for taking the time and effort.