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ColecoVision EPROM BIOS Conversion

Thanks go to Bruce Tomlin for figuring this one out. It looks like Coleco designed their system to make this conversion as easy as possible.

Subject: ColecoVision EPROM conversion
From: btomlin@crl.com (Bruce Tomlin)
Date: 1996/05/18
Message-ID: <4nldn4$n64@crl3.crl.com>
Newsgroups: rec.games.video.classic

Parts needed

28 pin IC socket
2764 EPROM chip programmed with the COLECO.BIN file
Two short pieces of wire
Soldering iron, solder, desoldering iron, etc.

(Note: If you haven't opened your ColecoVision before, you may have to use the desoldering iron to suck up some solder so that you can open up the RF shield and get to the circuit board. Also, you may want to consider repairing your power switch. Desolder it, take it apart, clean it, pack it with "dielectric grease" from an auto supply store, reassemble it, then resolder it.)

Desolder the old ROM chip. (U2) If you haven't desoldered chips before, get some practice or buy a pizza and split it with a friend who has. (See end of this file for tips on how to desolder an IC chip.) Also suck the solder out of the four extra holes, and out of the holes marked "WJ4" and "WJ5".
Insert the 28 pin socket into the holes and solder it down. Test your work by putting the ROM chip back in and turning the unit on. If the "COLECOVISION" screen comes up, everything is okay.
Solder short pieces of wire into the WJ4 and WJ5 holes.
On the underside of the circuit board are two small "bumps" in two short traces coming from the WJ5 holes. Cut the traces. Do NOT cut the long trace that ends in a "Y" next to a WJ5 hole.
Program a 2764 EPROM with the contents of COLECO.BIN, which can be found with the ColecoVision emulator.
Put the 2764 EPROM into the socket and test everything by turning on the unit and checking for the "COLECOVISION" screen. Now you're done!

Hints for desoldering:

I use a Radio Shack desoldering iron. This has a red rubber bulb on it and a hollow tip. It's cheap and works well.
Use a fresh tip for important projects! It's not worth trying to save two bucks only to ruin a circuit board or a chip. Tinning your tip is a good idea, too.
Wait for the joint to completely melt before sucking out the solder. If you suck too soon, you may not be able to melt the joint properly any more. Wait about four seconds, or five for the four "corner" pins.
When you have sucked out the solder from all of the holes, push all the pins to "crack" them off of the remaining solder.
If you have done everything right, the chip should practically fall out of the board.

So why would anybody want to replace the BIOS ROM like this? Anybody who's ever played on a Coleco and had to sit through that infuriatingly eternal startup delay can answer that one.

Put this modified BIOS in, and the splash screen goes away with a single press of the fire button.

Jay Tilton
06/28/98