Power supply 12v 2A repair problem

Thread Starter

Martiio

Joined Apr 2, 2020
37
I have a problem with power supply 12v 2A.It stopped working.When I opened the supply I noticed that the fuse resistor (or what ever is that) has burnt and the small transistor next to it.Can somebody tell me how can I find the value of burnt fuse and transistor?
 

Attachments

dl324

Joined Mar 30, 2015
13,320
No I can't,!
Can you trace the circuitry around the transistor and create a partial schematic?

Transistors in TO-92 packages have 3 different pinouts and two polarities. Without a part number or schematic, we can't determine which of the 6 it will be.

Cropped picture:
1632157683811.png
 

dl324

Joined Mar 30, 2015
13,320
Unfortunately I don't know how! I am newbie and this is my new hobby!
If you post a picture of the traces on the bottom of the board, someone might be able to show you how to do it.
It is a cheap chinese psu.
Those things can kill you. The Chinese are good at copying, but weak at innovating.

Those diodes may be okay. They're probably connected to line voltage. That's dangerous, but 1A would be okay on line voltage. I didn't try to understand what the rest of the circuitry might be doing.
 

AlbertHall

Joined Jun 4, 2014
11,534
Missed that. 1N4007 are only good for 1A continuous; kind of strange to use them in a 2A supply.
The 1N4007 are at the power input, presumably 115V/230V, with the 2A being the output. The rectifier is, I think, on the far side of the transformer.
 

Thread Starter

Martiio

Joined Apr 2, 2020
37
Repairing switch mode power supplies (whicj this is) is not a good place to start.
I have a few rectifier diodes 1n4007,if the fuse transistor is 1ohm(but how many wats I need?),the main problem is the small transistor! If I put wrong transistor what might be happened?
 
Top