[Coco] Coco 2 video issues

[Tormod Volden]

On Sat, Jul 18, 2015 at 3:52 PM, Francois Dion wrote:
>
>    I have a coco 2. It has been sitting for a few years. Just tried it out
>    recently during a retro tech meet at work (one of the tech meets I
>    started). Unfortunately it has some issues.
>
>    First issue, the character set seems to be coming from the wrong bank.
>    When it's powered on, the characters are the graphical set, instead of
>    saying stuff like BASIC etc, we see graphic sprites. So it looks like
>    there is a bit that's off (high bank of the ASCII set). I've reset the
>    ROMS and VDG and I've also cleaned and lubed the pins on those with
>    deoxit cleaner and deoxit lube. It didn't help.
>
>    On top of that, the NTSC signal gets too weak after about 30 seconds
>    and the whole thing becomes unreadable. Cocos are not my expertise, but
>    it seems like I have a VDG chip going bad? Before I go and order some
>    from china and wait months for it to get here, I figured I'd ask here
>    if anybody has a spare one, or know a US source for them.

I would also check the power supplies (especially -5V). A bad
capacitor can cause wrong voltages and issues with the video output.

Tormod