Colecovision - No Video

[abbub]

So...after my adventures with the Intellivision, my next ebay bargain showed up this afternoon...a nice, dusty Colecovision. Of course, like all ebay auctions that say, "I don't know if it works because I don't have a game/the video cable..." what they really meant was, "I tried to hook it up, but it didn't work so I threw away the video cable and set up a second auction for the games....sold as-is"

Anyway, ebay venting aside, does anyone have any experience/advice on Colecovision trouble shooting? I checked the power adapter. It's supposed to be sending 12, 5, and -5 volts, and it appears to mostly be doing that. The 12-volt line is actually sitting around 11.5 or so, but I'm not sure what the tolerance is. I cleaned the power switch throughly, because the few articles about Coleco repair mentioned that the power switches were notorious. No love there, but I did verify that it's got the proper voltages when switched on...seems fine.

The system doesn't through any audio/video when it's powered up. I know the switchbox/cable is good, because it works with the 2600 and the Intellivision. The TV does go a bit whiter in the fuzz department when it's switched on, but not enough to even consider it corrupted graphics or anything.

There seems to be a total lack of repair information for this thing on the net, which kind of surprises me... Any ideas/suggestions?

Thanks!

[channelmaniac]

First off...

Try turning it on with no cart in it. It should come up with a screen telling you to insert a cart.

If not...

Take the top off and check the voltages where the power supply jack connects to the game board with the game powered ON. If you are missing one of the power supply voltages then repair or replace the power supply.

If the game still isn't working then you could have one of many problems... bad clock circuit, bad CPU, bad video chip, bad RF modulator, etc...

[abbub]

You guessed it! Well...you guessed a lot of things, but one of the things you guessed was actually right! With the help of a donor part from a hanger queen, the Colecovision is now among the land of the living consoles! I'll explain in a second, but first, a brief message to the Coleco engineers:

Look, guys. I understand how hectic 1982 must have been. You guys were busy listening to Thriller and learning those dance moves to impress the ladies, arguing over whether to use beta or VHS to tape Knightrider, invading the Falklands, and ironing your parachute pants. Still, that's really no excuse. Three screws behind the main label to get the front panel off?! Yes, I KNOW there's a way to get the unit open without removing them, but it's a pain in my ass and is pretty much just a crap design. I'm sure your repair techs must have LOVED trying to pull that sticker off to get inside the chassis...or are they the ones that invented to the 'twist, pull, curse, and pull some more' method of getting the case open without removing the front panel? (Actually, getting it back on with the buttons properly lined up is the worst part...) Don't even get me started on your 'let's solder the RF shield to the logic board" antics...

Anyway, a buddy of mine also had a 'mostly dead' unit that he gave me. Actually, two of the chips on his unit had a bunch of diodes attached to it (that went nowhere) that made it look like it had been modded (or perhaps an attempt at repair?) at some point. It worked, but the colors were all wonky...white was green. I tried tweaking the few adjustments that the board to get the colors right, but finally realized that it was futile. Instead, I pulled the RF board off of the 'green coleco' and stuck it on my 'no video' coleco. Success! Donkey Kong in all of his glory. Or...at least, Donkey Kong with more glory than the Atari 2600 or Intellivision ports had to offer.

So now I just need to fix the controllers (one of them has no joystick, the other has no side buttons) and it'll be good to go!

[channelmaniac]

Cool,

Glad you got it fixed.

I repair & mod the CV units and have a few under my belt now.

They aren't hard systems to fix or mod if you are handy with a soldering iron.

The best thing you can do for it is yank that 4116 DRAM and upgrade it to 5v only DRAM like 4516 or 4164.

RJ

[abbub]

What will replacing the 4116 DRAM get me?

[channelmaniac]

More reliability and cooler running...

The 4116 DRAM takes +5v, -5v, and +12 to operate. 4516 or 4164 DRAM takes +5v only.

RJ

[abbub]

Nice. That's good to know. Thanks.

[channelmaniac]

I put a post up on my repair logs site about converting the system to run those 5v only DRAMs.

http://newlifegames.net/nlg/index.ph...11121#msg11121

RJ

[abbub]

Man, that's an excellent site overall. Good information! How come that didn't come up in my google searches?

[channelmaniac]

Thanks!

I keep my repair logs out there in hopes that they help others keep their systems running for years to come.

Also, it's a good advertisement of what I can fix if someone doesn't want to do it themselves.

RJ