wrote:


I have a Commax CDV-43k/DRC-4L (Stock Code: PI-1176) intercom that isn't working anymore. It seems the power supply board in the intercom (CDV-43K) itself (converting wall power of 220v to 15v) has blown. I think it might be the transistor (see photos: https://imgur.com/a/uBCXjwQ). The suppliers say that it is out of warranty and that I would have to buy a new one.

Here is a link with a few photos of a circuit board that isn't working anymo
https://imgur.com/a/uBCXjwQ

I have tried searching online, but couldn't find anything that gave me any indication of the specs of the transistor or what transistor to try and replace it with. I also tried to search for the schematic, but couldn't find anything.


** Take about 15 minutes to trace that schem yourself.


If anyone can perhaps help me identify the blown transistor or perhaps
point me in the right direction that would be greatly appreciated.


** Looking at the copper side of the PCB, I can see the blown 3 pin device is driving the LED inside the opto-coupler for feedback.

There is a small heatsink behind the chip, so a TL431 is a good bet.

The opto will be cactus too.

What happened ?

Either the opto flashed over ( very rare ) or a foreign metal object did the trick.


..... Phil