Need help with Coleco repair - broken video

[BussardRamjet]

Hello folks,

 

I am a recent owner of a ColecoVision and a few games.

 

The Coleco was working fine for a while (even though I installed a composite mod) but suddenly all I am getting is broken video - see photo below:

 

I am not really an expert diagnosing this - I tried multiple games but all I get is this thing plus correct game audio. So I think the CPU is fine - it is playing the game I just cannot figure it out what is suddenly wrong with the video.

 

I have measured input voltages unloaded - just the output pins of the power supply and I got the following values:

5.11 V

-4.87 V

11.93 V

 

This seems fine as far as I can tell.

 

Do you guys have any tips - any chance that this is related to the power switch? What should I do next? Open it up and start measuring voltages inside? What would be the best way forward?

 

Thanks a lot in advance!

 

ps: This is the mod I have installed - it worked fine for a few hours or so - hopefully it is not related and it is just a weird coincidence:

http://www.ebay.com/itm/ColecoVision-A-V-Composite-Video-Mod-Kit-NTSC-PAL-DIY-/181061180246?var=&hash=item2a28165b56

​

 

[+nanochess]

I would suggest to undo the video mod and check if the RF output still works.

 

If it works, then redo your video mod, otherwise you have fried the VDP chip or something in the RF module.

[NIAD]

Does this video mod eliminate the RF Video output? It really shouldn't. If the RF output is still intact, test your system by this means. If the RF output has been disabled, then follow Nanochess' suggestion above.

 

You basically have to play doctor in order to find the problem. If the system was working properly before the video mod, then the problem obviously would be the video mod board or your installation of it.

 

If it ends up being the mod board you bought, I would highly recommend that you replace it with Yurkie's Composite Video with Audio mod board that sells for around $20-$25. It is a professionally designed and manufactured PCB unlike this bread-board mod board you bought.

 

Just send Yurkie a PM as well as check out his pinned thread for full details of all his services and products.

[BussardRamjet]

The mod does not eliminate the RF video out - and I get exactly the same picture with both the RF out and the composite out.

 

I was just so happy and relieved that it worked for a few hours - I am not really experienced with the soldering iron.

I was playing Quest for Tires and Zaxxon - swapped it out for Venture and this is what happened.

​

Anyway, you guys are correct - I will open it up and check the soldering of the mod, remove it and see what happens.

 

Thanks!

 

Btw, the image above does not change as I try playing a game - it is pretty much a constant pattern.

[mightywiz]

could be a faulty power switch.