Microelectronics | 12 V / 2 A Switching Mode Power Supply

Synopsis

This power supply went shot a few years ago an I didn't bother fixing since I had little use for it.

As I plan to use it, I decided to invest some time (and resources) to completely rebuild it with quality parts in order to increase its reliability.

Maintenance

First of all, I stripped away all the parts. Next, I replaced almost all components with high quality counterparts. Next, I cleaned the circuit board with acetone and isopropyl alcohol. I used quality eutectic solder to bind all electronic components.

Pictures

Here are some pictures that I took during this operation.

This is before the rebuild.

This is the bare PCB.

And after the rebuild.

These are the parts that I replaced. ChongX VEHT! Man, ChongX - I can understand it. But veht instead of vent?

Next, I extracted the schematic diagram on a piece of paper. Then, I modified two resistor values, so that the divider calibrates the supply voltage to 7.5 V. I plan to use it in an equipment that accepts between 7 and 12 V as input voltage. Its own power supply is constructed around a 7805-class linear voltage regulator. Supplying this equipment with only 7.5 V, reduces heat losses in this circuit section. Of course, I can modify this power supply to output 5 V directly. But I don't want to further modify the device that will receive this PSU.

This power supply will operate in an always-on fashion; thus, it had to be reconstructed with quality in mind.