ATX conversion to bench power supply (fixed & variable)

hello my friends and welcome my name is zorin and today I will show you how to modify an old ATX power supply into a lab power supply with fixed and variable outputs [Music] I have this ATX power supply at home from an old PC but first I need to make sure that it works because I already have other broken power supplies to turn it on I will short the green wire with the black one Let's test the 12 volts rail using my volt ammeter I will connect the simple ceramic resistor as a load but with the current consumption of only 2.4 amps the voltage drops almost to 11 volts on the power rating table it says 19 amps for the 12 volts rail so why is that let's measure the voltage on a separate pair of yellow and black wires the voltage is better these thin wires cannot carry a lot of amps so I need to use more of them in parallel or replace them with thicker wires be careful with the big capacitors they may still be charged with a high voltage and can shock you as you can see this power supply is old it only has one 12 volts rail but it looks very clean I don't think it has been used much I want to thank all my patrons for their support if you want to see these videos a few days earlier and more DIY videos and updates about my future Projects please check out my patreon page for this project I will mostly use my ugly and Powerful soldering gun my favorite the case will be modified so I will remove everything wires connectors the cooling fan and the circuit board now it's a good time to inspect the circuit board capacitors are usually the first to fail but these look good the back metal panel will become the front panel and I will replace it with a piece of four millimeter plywood I will reposition the cooling fan on the top panel so I measured and made the paper template and then I used it to Mark the hole on the metal case to cut the metal panels I will use my small and underpowered rotary tool safety goggles are mandatory and here we go oh boy this will take a while and after only four hours I finished all the cutouts I used some sandpaper on the edge of the hole so it's pretty smooth now I also made the cutout for the mains connector the metal case is almost finished I just need to sand the panels and clean them these are the components I will use for this project I need to figure out how to position all of these on the front panel my OCD tells me to arrange them in a symmetrical way so I marked the position of each component on the panel the cutouts will be made with a small cutter if I use an electrical jigsaw it will break the plywood I will drill some four millimeter holes for The Binding posts and I will use this chamfering bit to make the hole smoother and also some sandpaper to make the Surface smoother I cleaned the panel now it's time to make it more appealing to the eyes so I bought this gray self-adhesive vinyl wrap and I'm going to apply it very slowly to the panel I have to pay special attention to the corners and now the cutouts and the rest of the holes the plywood panel is finished I want to cover the entire metal case with gray vinyl I will apply it very slowly because I don't want air bubbles under the vinyl I also need to cut the vinyl covering all the holes the case is ready for the next step I will cut the wires I don't need from this circuit board because I will use only the three main outputs red is positive 5 volts black is ground obviously yellow positive 12 volts and orange including the sense wire 3.3 volts the green wire turns on the power supply from standby when you push the button and short it to ground but I'm going to remove the green wire and Bridge it directly to ground because I don't need the standby function there is still some work to do on the circuit board but I will put it back in the case for now if you mount The Binding post on a metal panel they need all the plastic parts to insulate the terminal from the metal panel but I will place them on a plywood panel so there is no need for the plastic insulator I like these binding posts because they also have small holes to connect bare wires without any plugs I will temporarily fix the front panel in position with two screws as I said these wires are very thin I think they are 0.7 Square millimeters so I will measure and cut 4 wires for each binding post the wires will be connected to the binding posts with terminal logs and for a good contact inside I will also fill it with solder it's a bit difficult to tighten the screws in this crowded space especially if you have sausage fingers for the 12 volts rail I will use 2.5 square millimeter wires and I will split it in two one wire will go to the fixed voltage binding post and the second wire will power the back boost converter for the variable output you may be wondering why I didn't use the plus minus 12 volts outputs to power the converter with 24 volts the converter will work much better with a higher voltage right well there is a good reason for that if you know why please leave a comment below and let's see who's the first to answer correctly yes thank you the sense wire of the digital voltmeter will be connected to the positive output of the converter to measure the variable voltage directly on The Binding post for the USB port I will use two red wires and the thicker wire for the negative pin I will hold the USB port in position and fix it on the panel with hot glue it looks ugly in the back but the front is nice that's a phrase that no one has used before this is the thick negative wire coming from the ammeter output the volt ammeter will be powered together with the dummy load resistor from a 5 volts wire I will stick the ceramic resistor to the case with double-sided tape if the resistor warms up the entire metal case will act as a large heat sink if the volt ammeter is powered by the same power source it is measuring then this black thin wire must be cut otherwise the negative voltage will bypass the internal shunt which is also connected to negative and the current measurement will be wrong these are the ammeter wires and theoretically this ammeter can measure up to 10 amps but let me show you something check out how thin this wire is is it really able to carry 10 amps without altering the measurements look how thin it is compared to the other wires I'm using so I will replace it with a thicker one and for a good contact I will solder the wires directly to the ammeter pins this constant current constant voltage buck boost converter will be used for the variable output four standoffs need to be added to mount the converter on the metal case I will replace the two multi-term potentiometers with bigger ones according to this schematic I'm going to add some large washers in the back because I don't want them to stick out too much in front of the panel the converter and thick wires are in position so I can connect them now in the back of the power supply the mains connector will be fixed to the case with two screws the main switch is next after I find it the hole for the motherboard cables is perfect to hold it I have only one more wire to connect the fan will be connected to a 5 volts wire because I want it to be silent and last longer I will start it for the first time let's hope nothing blows up no fireworks that's disappointing for somebody I checked the outputs everything works there is one small problem though when I decrease the voltage on the variable output it has a delay of a few seconds there is probably a capacitor at the output of the converter that holds the charge but when you connect the load and decrease the voltage is fine if this doesn't bother you you can leave it as it is but I want to improve the response time this is a 3 watts and 3.9 kilo Ohm resistor if I connect it as a load the voltage can be lowered fast the current consumption is too low to be picked up by this GP ammeter so I insulated it with heat shrink tube and solder it directly to the output of the converter it will not alter the ammeter readings the converter will be mounted around here and I need to make sure the wires don't touch the radiators and now I will slowly install the top panel and check the wires inside I need a protective grille for the 80 millimeter fan I will Salvage it from this broken power supply and I think it will look better with black screws so I will take some from Another Broken power supply black screws on the front panel as well on the bottom panel I will give it four self-adhesive rubber pads let's finish this project by adding two nice knobs for the potentiometers the power supply can be turned on from the main switch in the back there is no need for a standby button let's check the outputs 3.3 volts 5 volts on the 12 volts output the voltage is a little higher but it's okay and the variable output I will test it with the 55 Watts car light bulb on the 5 volts output first 2.4 amps with 12 volts it draws almost 4 amps and the variable output let's check the current limiting adjustment this chip constant current constant voltage converter seems to be very good I already have an older variable power supply and the fixed voltage one but my new power supply will replace both of them it's more colorful so I think it looks better and it was cheaper to make but the downside is that these two are more powerful so this is my new power supply with fixed and variable outputs if you enjoyed this video please share it leave a comment below and hit the like button bye

Channel: Sorin - DIY Electrical Nerd

Views: 75,844

Keywords: atx psu, power supply, conversion, bench, lab, diy, no 3d printer, how to, cc/cv converter, project

Id: eEs8nVUB72k

Length: 12min 57sec (777 seconds)

Published: Sat May 20 2023