Colecovision mod problems - any ideas?

[samplefiend]

Hi all

 

I recently got my hands on a modded Colecovision console with a pause button, new bios and av mod. Unfortunately I had problems with it from day one and had to resort to trying to fix it myself. I got it imported from the USA to Scotland so sending it back for repair was going to cost me a lot more money and I'd already paid a fair amount for the console and then for games and a flashcart.

 

The original problem went like this. When using the AV mods I could get sound once i got a game running but no picture. If I used the RF output i could get a black and white picture but no sound.

 

You can see what i mean if you download or view this video : www.satellitedub.com/colecovision.avi

 

It shows the RF output then the AV output then back to the RF output.

 

I opened up the console and there seemed to be problems with the 1K Potentiometer. I got a new one and fitted it into the console. Now I can get a picture and sound using the AV output but it is only in black and white not in colour. It does the same thing on 2 different TVs. I tried moving the channel selector switch from 3 to 4 but it didn't make any difference. Also there is now some background noise and a slight whine when playing games which wasn't there before!

 

Anyone got any suggestions for what might be wrong and what i should do please? My TV is NTSC compatible and plays my other NTSC consoles (neo geo aes / mvs etc) in colour without any trouble.

 

Thanks in advance for any advice,

 

Craig

[ten-four]

Hi Graig.

 

Have you tried a Tv without your Scart converter, I mean do you have a tv with AV composite. (red-yellow-white) ?

 

Try to connect AV direct.

 

And have you checked the Mod. for loose wires inside. ?

[samplefiend]

Hi dragonstomper.

 

Thanks for the tip mate. I connected the Coleco to my TV using the AV inputs instead of via a Scart adapter but the results were the same. A black and white picture instead of colour ...

 

I also haven't been able see any loose wires within the mod itself (the only loose one seemed to be the potentiometer connections which i fixed when i replaced it) although I'll be able to have a closer look tomorrow in the daylight just to be sure.

 

Thanks for the advice though, much appreciated! :-)

 

Craig

[ColecoDan]

Did the seller say it was previously tested or sold as is because I would have returned it instead of going through all these headaches?

 

You could pm Yurkie in case he misses this thread and ask him for ideas since he fixes a lot of colecovisions.

[+5-11under]

I'm assuming you tried to adjust the 1K potentiometer for the best picture?

 

With the 1k potentiometer, this sounds like a standard "Ben Heck" video mod. Look it up at his site, or check out my version here: http://www.atariage.com/forums/topic/163446-diy-modifications-for-colecovision/?do=findComment&comment=2019142.

 

It sounds a bit suspicious that it wasn't working at all, then after the "fix", it only shows black and white. Perhaps something else is still wrong with the mod circuit (try shorting out the potentiometer), or a component in the CV has broken (the LM1889 perhaps?).

 

I'd check closely for any shorts or opens at or near the modified areas. A cheap attempt would be to swap out the transistor. Also check for proper +12V operation... although if the original video RAM chips are there, they need the +12V to run, also. Also verify the mod circuit. Perhaps the ground has been lifted.

[samplefiend]

Hi there Coleco Dan,

 

The seller said the console was fully working and we tried to work something out (if i returned it though i'd have ended up nearly £200 out of pocket because of the original postage, return postage, tax etc and would only have got about £50 back) and then accused me of trying to cheat him as he didn't believe there was any problem even though i'd sent a link to a video showing what was going on. Ah well, it's the first time i've got a bad console in all the years i've been collecting ... these things happen to us all at some point unfortunately.

 

Hi there 5-11 Under,

 

I adjusted the potentiometer from closed to fully open but all i can get is a black and white picture unfortunately. if I open it up fully the picture gets really bad but when open about a third I get a nice clear picture but only in black and white. I'm not an expert with fixing things so to be honest I'm not sure I could follow your suggestions although i'll do my research and give it a go! Hopefully what you've suggested will cover what is going wrong and means I can get it working in colour now. :-)

 

Cheers to you both for your help with this,

 

Craig x

Edited July 11, 2012 by samplefiend

[+5-11under]

These are sometimes tough to fix, especially without having the unit in hand. Maybe there's someone local who can help out with the technical side.

[RelliK111]

Hi there Coleco Dan,

 

The seller said the console was fully working and we tried to work something out (if i returned it though i'd have ended up nearly £200 out of pocket because of the original postage, return postage, tax etc and would only have got about £50 back) and then accused me of trying to cheat him as he didn't believe there was any problem even though i'd sent a link to a video showing what was going on. Ah well, it's the first time i've got a bad console in all the years i've been collecting ... these things happen to us all at some point unfortunately.

 

Hi there 5-11 Under,

 

I adjusted the potentiometer from closed to fully open but all i can get is a black and white picture unfortunately. if I open it up fully the picture gets really bad but when open about a third I get a nice clear picture but only in black and white. I'm not an expert with fixing things so to be honest I'm not sure I could follow your suggestions although i'll do my research and give it a go! Hopefully what you've suggested will cover what is going wrong and means I can get it working in colour now. :-)

 

Cheers to you both for your help with this,

 

Craig x

 

Did you buy it on ebay or through some private listing?