colecovision video problems

[bah]

I'm new to colecovision but I am trying to refurb a broken console. The unit boots to the main screen but the words and graphics are messed up. With a cartridge in (donkey kong) the sound is clear and you can see the game in demo mode, but can't play it.

 

The power switch is clean.

 

Any ideas or on-line service manuals out there?

 

Thanks

 

bah

[channelmaniac]

I'm new to colecovision but I am trying to refurb a broken console. The unit boots to the main screen but the words and graphics are messed up. With a cartridge in (donkey kong) the sound is clear and you can see the game in demo mode, but can't play it.

 

The power switch is clean.

 

Any ideas or on-line service manuals out there?

 

Thanks

 

bah

 

Can you post a picture?

 

Does it boot to the garbled mess even with a cartridge out?

 

If it looks good with the cartridge out then suspect a dirty slot or cart.

 

If not, check the power supply, switch, and the 4116 DRAM ICs.

 

Raymond

[bah]

Raymond,

 

Thanks for the reply. I have a second console that plays fine with the same power supply, so I ruled that out. Next I took the switch apart and cleaned it as well as unbent the contact sliders slightly for a good connection, but the problem persists.

 

The initial boot screen always looks the same or nearly so. The words are partly scrambled letters, mostly readable but a few are nonsense shapes. There is also a dark vertical line through each letter. Screen reads:

 

PORJ CAIA KBB

BABKRA IJSARPIJC CARPRI@CA

KR AXPAJSIKJ IK@QHA*

1982 CKHACK

 

I can't get a pic up tonight but perhaps you could guide me to locate and test the 4116 DRAM IC. Is this a common failure and are parts avialable?

 

Thanks again,

 

Brent

[channelmaniac]

Replace the 4116 DRAM IC at location U15.

 

I have some available on my website.

 

RJ

Edited September 10, 2008 by channelmaniac

[bah]

RJ,

 

I found the U15 location. The chips on my board are NEC D416C/2. Are these chips close enough I can substitute the 4116 or do I need to find the D416c/2 ones? At any rate I did not see any reference to the number on your web site.

 

BAH

[ten-four]

RJ,

 

I found the U15 location. The chips on my board are NEC D416C/2.

 

BAH

 

I can understand that there are several different, when my chips states:

 

B 8317

MM 529 ON-3 !

 

 

But as I understand it, they have the same function.

[channelmaniac]

I checked my site and it says I'm out of those... I'll double-check inventory tonight and update the site.

 

Yes, the MM5290 and the D416 are the same as a generic 4116 part number.

 

Be careful when removing the old chip as you DO NOT want to lift a trace or pull out a plated thru hole.

[bah]

Thank you much guys.

 

BAH

[480peeka]

Use some contact cleaner on the power switch and check the solder joints on the power switch. Mine I had to resolder the power joints and lubed the switch and now it works great. If that does not help, check and see if you can use another power source.

 

I'm new to colecovision but I am trying to refurb a broken console. The unit boots to the main screen but the words and graphics are messed up. With a cartridge in (donkey kong) the sound is clear and you can see the game in demo mode, but can't play it.

 

The power switch is clean.

 

Any ideas or on-line service manuals out there?

 

Thanks

 

bah