Microelectronics | 12 V / 2 A Switching Mode Power Supply

Synopsis

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

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

Maintenance

First, I stripped away all the parts. Next, I replaced almost all components with high quality counterparts. Finally, 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.

These are some of the cheapest electronic components I have ever seen.

This is the bare PCB.

And after the rebuild.

The solder side is OK.

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.


Copyright © 2004- Alexandru Groza
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