Want to convert a computer ATX power supply into a high-amperage, adjustable lab power supply? In this step-by-step tutorial, I'll explain how to easily modify a PC power supply based on the TL494/KA7500 integrated circuit to vary its output from 4V to 25V and disable overload protection to utilize its full power.

This is an ideal recycling and electronics project for your workshop, perfect for charging car batteries (13.5V), 6V batteries/UPS (7.4V), or powering any circuit under test.

📌 Key points explained in the video:

Step 1: Disabling the protection: How to connect pin 4 of the integrated circuit (TL494/7500) to ground/negative to prevent it from shutting down under heavy loads.

Step 2: Replacing capacitors: Changing the 16V output capacitor to a 25V/35V capacitor to safely handle the increased voltage.

Step 3: Regulation Circuit: Cut the trace at Pin 1 and install the 50k potentiometer with a 1k resistor.

Final Assembly: Install in an enclosure with a digital voltmeter, connection terminals, and an adjustment knob.

⏱️ Timestamps / Chapters:

0:00 - Introduction and initial overload test
01:15 - Identifying the compatible IC (KA7500 / TL494)
01:34 - Step 1: Removing the protection (Pin 4 to ground)
02:04 - Step 2: Potentiometer (50k) and resistor (1k) connection diagram
03:02 - Step 3: Replacing the 25V output capacitor
03:36 - Demonstration of the protection bridge and test with a light bulb
05:25 - Cutting the trace on Pin 1 and soldering the potentiometer
06:48 - First voltage regulation test
07:46 - Assembly in chassis with digital voltmeter and terminal blocks
08:20 - Final test reaching up to 25V
🛠️ Components and materials used:

ATX power supply (with IC) TL494, KA7500, or equivalent.
50kΩ linear potentiometer.
1kΩ resistor (brown, black, red).
25V electrolytic capacitor (1000µF or higher).
Digital voltmeter/panel meter.
Terminal blocks/connection terminals.
Soldering iron and solder.

⚠️ Safety warning: When working with switching power supplies, always disconnect them from the mains power supply before handling the board. Since the overload protection has been removed, be careful not to create direct short circuits between the output pins.

💬 Your opinion matters! What kind of projects would you use this adjustable power supply for? Let me know in the comments.

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