Hello, since it was a bit difficult to make, I will give you a series of explanations so that you can proceed according to it and it will be easier for you. What should I do?
We proceed as follows:
1_ I take a picture of the output capacitors
2- We separate the capacitors and output wires from the board
(If you cannot distinguish which capacitor belongs to which voltage line, replace all the output capacitors with the same capacity with 50 volts, for example, if 1000 microfarads are 16 volts, put 100 microfarads at 50 volts)
In this way, the discussion of capacitors is over and you do not have a problem about it
3- IC 494 or 7500 (it doesn’t matter which one) you find it and disconnect one pin from the circuit.
4- Next, we go to IC pin number four, if you follow the copper lines under the board, you will come to a crossroads, one of which is connected to a resistor that is connected to the ground on the other side of the resistor, hold this, and cut that one crossroads with a cutter. .
5- Now we take a 2.2 kilo resistor (half watt or one watt) and solder one end to the ground, and one end to the number one base.
6- Now we have to take a 33 kilo ohm resistor (half a watt or one watt) and connect one end to the place where 12 volts used to be (the yellow wire was connected) which is written 12V on the board. IC number one.
7- We take two strands of wire and solder 33 kilo resistors to the left and right
8- We have to connect two, one 20 kg and the other 1 kg, that is, solder the right leg of one to the left leg of the other one.
9- Now each of the volumes has two free pins, one of the wires soldered to the left and right of the 33 kilo resistance is soldered to the two empty pins of one volume and one wire to the two pins of that one volume.
10- If you did not replace the capacitors at first, replace the 12V, 3.3V and 5V line capacitors with 50V of the same range.
11- We connect one red wire to line 5, three black wires to GND, two yellow wires to line 12 and two orange wires to line 3.3. (It is obvious on the board itself, these wires were in these places from the beginning, so that they are not in your hands, we brought them in and only re-placed the ones we needed)
12_ Solder the negative wire of the fan to one of the black ones and the positive one to the red wire and that’s it
13_ I solder the two black wires of the power to the black wire of the ammeter, and the red wire to the negative socket.
14_ Now I solder my positive voltage output socket to the middle pin of a three-pin rocker switch
15_ I solder two yellow wires to one of the bases and two orange wires to another base.
16_ We are going to connect the wires of the voltmeter, it has three red, black and yellow wires
The black wire is connected to the negative output socket
red wire to yellow wire (yellow wire coming from power)
Solder the yellow wire to our positive voltage output (the middle base of the rocker switch).
17_ We separate one of the 220V input wires, we put a thumb switch on it and off on its way.
18_ It is finished, enjoy
I will give you some photos to help you more
This post is written by Mobin_mbm