Colecovision BIOS Replacement

From TechWiki
Jump to navigation Jump to search

Purchase a BIOS and socket as a kit

Purpose of this modification: For no explainable reason, the factory Colecovision BIOS forces you to stare at the title screen for what feels like an eternity.

If you're already delving into the guts of your Colecovision to clean the power switch, upgrade to 5 volt RAM, or add a video modification, you might as well replace the annoying BIOS while you're in there.

I've heard this mod called the "no-delay" or the "intro skip". The popular replacement has the timer hacked out and enables the start of the game with the press of a controller button.

Parts List
Replacement BIOS chip
2 bits of wire, like clipped leads from a resistor or something similar
28-pin socket (optional, but highly recommended)


Step 1: Disassemble the Colecovision

Disassemble the Colecovision and remove the PCB shielding.

BIOS and WS4/WS5 desoldered

Step 2: Desolder original BIOS and remove jumper solder

Desolder the original BIOS and the 4 adjacent solder vias (the OEM BIOS is only 24-pin, the replacement chip will be 28 pin). Two locations beneath the BIOS are labeled WS4 and WS5, those should be desoldered as well.

Bottom of PCB, WS4/WS5 connecting pads severed

Step 3: Cut connections between WS4 and WS5

Flip the PCB over and look for the WS4 and WS5 vias. There are 2 traces with circular pads connecting WS4 and WS5 together. Those connections need to be severed, using something like a hobby knife or a thin metal file.

Step 4: Install jumpers and socket

Jumpers and new BIOS socket installed

Solder in connecting jumpers across the pads for WS4 and WS5, and the 28 pin socket (make sure the notch is facing the same direction as the notch in the white board silkscreen.

Step 5: Install new BIOS and test

Insert new BIOS chip, connect video and power, and recheck that your Colecovision is functioning.