Fix a VIC-20 displaying the wrong colors

Last Updated on March 13, 2021 by Dave Farquhar

It’s not terribly uncommon for a VIC-20 to display colors badly, or just downright wrong. Most people attribute this to the nature of the machine. But it’s possible to adjust the color to get something closer to what screenshots in vintage magazines suggest the VIC-20’s display really looked like. Here’s how to fix a VIC-20 displaying the wrong colors.

The VIC-20 never had great color rendition to begin with, but as the components age, the color can drift even further. The VIC-20 has two potentiometers on its motherboard that you can use to adjust the color.

My VIC-20’s screen looked like a C-128

Fix a VIC-20 displaying the wrong colors
To fix a VIC-20 displaying the wrong colors, look for the two potentiometers on either side of the R33 marking, near the center of this picture.

The VIC-20’s startup screen is supposed to be blue text and a blue border with a white background. Mine displayed green text on a gray background with a green border. It looked like the startup screen of a C-128.

I tried some games, and depending on the game, the screen looked fine. Commodore’s Avenger, a blatant Space Invaders clone, looked just fine because it used a black background and bright colors.

I wondered if someone preferred a green-on-gray color scheme and just burned themselves a custom ROM to change the startup colors. A fair number of VIC-20s ended up in the hands of tinkerers, so that kind of customization isn’t inconceivable. But when I used the CTRL and number key combinations to cycle through the text colors, I saw that white was indeed displaying as dark gray, and blue was displaying as green. That confirmed this wasn’t a custom ROM. The colors were wrong.

Some people would immediately order a replacement video chip, or replace the capacitors on the board. But the video chip is proprietary, and unique to the VIC, so they aren’t super easy to find. Replacing the caps isn’t necessarily a bad idea, but it’s time consuming, and not always necessary. Yes, these caps are old. But most VIC-20s didn’t get the years of use the 64 and 128 did, and the VIC-20 came during the days when Commodore could afford quality components. There’s no need to assume the caps are automatically bad, like they are on AGA-era Amigas.

Adjusting the VIC-20’s video to fix the wrong color display

There are two potentiometers near the VIC-20’s video chip that adjust the color of the video. Potentiometers are small plastic pieces that have a dial with a slot in them that you turn with a small screwdriver. You can think of them exactly like the knobs on old CRTs that let you adjust things like the brightness, contrast, hue, and other nuances of the display.

Commodore assumed most people would connect the VIC-20 to a TV through an RF modulator. So today, when we use the composite inputs on a newer TV or a monitor, the color isn’t necessarily optimal. Plus, the colors may have shifted due to various components aging.

To adjust it, you have to open your VIC-20, then connect it to the display and power it back on and adjust those potentiometers until you’re happy with the display. Then you can power down, disconnect, and reassemble.

Disassembling the VIC-20

Disassembling a VIC-20 is a lot like disassembling a C-64. There are three screws on the underside. Remove those three screws, flip the unit back over, and pull the front toward you. If you use the back of the machine like a hinge you’ll damage it.

Disconnect the power LED, which is a three-pin connector on the right side of the board, then if you wish, disconnect the keyboard or set it to the side.

Locating the potentiometers that adjust the color

Fix a VIC-20 displaying wrong colors
A real VIC-20’s display will never look quite as good as an emulated one, but you can use this picture as a target.

The potentiometers sit in between the video chip and the video port on the back of the machine, near the center. Most VIC-20s have a metal box over the whole video circuit to cut down on interference. Pop the lid off the metal box, and the potentiometers are inside the box. If your VIC doesn’t have the box, just look for two plastic pieces that look like you can turn them with a screwdriver, near the video port.

Once you locate the potentiometers, carefully hook your VIC-20 back up to your display and turn it on. Be careful not to drop any metal parts on the VIC while you’re adjusting it. Turn the pots very slowly, paying attention to their effect on the color. Resist the temptation to turn either of them all the way up or down right away. A minor adjustment may give you the best picture you’ll get. The colors will never look quite like a C-64, and the picture will never be as clear as it looks in an emulator like VICE. In my case, I never got cyan to look right. My VIC insists on displaying light green. Cyan should be a blue-green. But at least I got white back. I think I need that color.

Once you’re happy with the picture, power down your VIC-20 and disconnect it. That’s how you fix a VIC-20 displaying the wrong colors.

Reassembling your VIC-20

Plug in the keyboard if you removed it, being careful to line the connector up correctly. You shouldn’t see any pins. Then connect the power LED back up.

The trickiest part about reassembling a VIC-20 is the hinge in the back. There are three tabs on the top half of the case that line up with slots in the lower half. Make sure you reconnect the internal parts first, before tackling this part. Line it up, then try swiveling the two halves up and down to make sure everything lines up. It’s easy to break off tabs if you don’t line them up correctly. When you think you have it, check the sides and the back to make sure you don’t have any gaps. If you see gaps, the tabs aren’t lined up. Once you get everything lined up, replace the screws on the underside of the machine. Now you’re done.

If you accidentally break off any tabs, you can glue them back into place with some 5-minute epoxy. Give it some extra time to cure before you reassemble the case.

Enjoy your newly adjusted VIC-20!

One other potential VIC-20 malady

Early VIC-20 power supplies with the two-pin connector are reliable. But later VIC-20 supplies that use a C64-style DIN connector are not. To continue using a later VIC-20 safely, get a heavy duty 64 power supply, or build your own. The VIC-20 won’t overburden a 64 supply, but the 64 power supply fails in disastrous ways, so getting a heavy-duty box that fails safely is good insurance for your VIC-20.

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