A Very Cheap Lab Bench Power Supply

I made a lab bench power supply, since I didn't have one. I decided to use the most ghetto option by scrapping together random trash from my workshop and as it turns out I only had to buy 2 components for this thing to work.

To make this you will need a few things which can actually just be made to your liking.

The LM317 DC-DC step down converter it is the heart of this project and we will use it. This kit offers short circuit protection and limits the current quickly enough so there is no damage, adding a fuse in series with the positive output isn't a bad idea cause it will save the LM317 from cooking itself when there is excess load.

https://www.aliexpress.com/item/32342205342.html

This is the purchase link to the converter, we will also need the following

1. A 4700uF capacitor
2. A bridge rectifier
3. A mains 220V transformer to any voltage that is max 35V
4. A 10kOhm potentiometer
5. A LED voltage indicator (0-100V i doubt :-) )
6. A few banana plugs

If you wish to have the LED voltmeter keep in mind you will need a second transformer for this, because by connecting it to the output and adjusting the voltages below 2V it stops working.

To make this construction as stated above you will need the LM317 kit, wire it accordingly to the scheme above.

I am very sorry its bad, I was in a rush.

C1 is 4700uF 63V capacitor and the bridge rectifier you can salvage from a PC power supply, i used GBJ3512. The other bridge rectifier on the second transformer is M250C80 which is selenium and very old.

I haven't tested the specs of this power supply but I only tested the short circuit protection and its good. If anyone wants to criticize my design they are my guest to do so. This was all made from random electronic garbage and only took 30 minutes (without searching for the components to assemble).

All the scrap parts are:

1. The case is from a old Bulgarian power supply that was made to power a radiotelephone РТ21-10 I recieved the case, the internals (a custom transformer) as a gift from one of my relatives who was a TV repairman. He had a go of making it a power supply succeeded but it died so he gave me the rest.
2. The second transformer is from a old power supply for a phone Siemens
3. The indicator light is from a old oven
4. The button for on and off is from a old Soviet televisons back panel.

This project proves that the hoarding tendencies always win, hah im kidding. It just proves that you can make anything with things you have at home. Stay safe and happy soldering!