Category: Power Supplies

My old power supply didn’t have a current limit and was not protected against short circuit.

This is the second time I change the circuit in this power supply, the previous time I replaced the original circuit by this one:

I changed the circuit to this one because the original burned out after a short on the output terminals.

The case:

I wanted to have a higher output voltage then the original, therefore I used a 2*12V 2*5A transformer I had lying around (bought it at a garage sale).

The ciruit I’m going to use this time:

Source.

The display print covered the entire front off the power supply. Because of that there was no space to put an extra potmeter to regulate the current, so I decided to build new voltage and current meters.

The circuit that I used for that:

For the missing resistor value’s see: fig. 1 en fig. 2.
Source.
Datasheet ICL7107.

The power supply and capacitor pcb’s are ready:


Printlayout


Printlayout

Mounted:

I mounted a new heat sink because the old one wasn’t big enough.

(The bracket is used to press a TO-220 heat sink to the head of the transistor for some extra cooling)

The supply for the panel meters had to be isolated from the main power supply, so I build a small pcb with 2 7805 powersupplies.

Mounted:

The panel meter pcb almost finished.

Today I made the front panel. It is printed on photo paper and glued to the front. The result:

The ZN458A diode’s where hard to get. Then I got a tip from Sine, he used the TS431 as a replacement part. I’m receiving those tomorrow, so I can complete this power supply.

This circuit comes in the place of the ZN458A:

Today I received the zener ic’s, and soldered them in. The power supply is now finished.

The displays are not as bright as it may appear on the picture.