Task: Improve the Brightness of the Composite Video from a Commodore 64 by Adding a Resistor to a Revision A Circuit Board
Needed: Commodore 64 with Revision A circuit board, 220 Ohm resistor, soldering iron
Time: 15-30 minutes
Introduction
The oldest Commodore 64s have a Revision A circuit board that produces dimmer than desired composite video output. The dimness can be attributed to a 300 Ohm resistor in position R10 next to the VIC-II chip. This can be fixed by replacing the factory-installed resistor with one that is around 120 Ohms. Alternatively, you can piggyback a 220 Ohm resistor that together brings the resistance down close to 120 Ohms. This is the mod that I decided to do.
Instructions
First, make note of the brightness of the video before the mod for comparison.
Second, open up the C64 case, confirm it is a Revision A circuit board, and identify the R10 resistor next to the VIC-II chip. You may need to remove the RF shielding from the unit and the video circuitry.
Third, solder in the 220 Ohm or similar resistor on top of the one that is there as shown below. Resistor kits are readily available on Amazon.
Finally, test the new video and compare to the pre-mod brightness. Below are photos before and after the mod.
Comments
This is an easy mod if you know how to use a soldering iron. The results are quite striking!