[Coco] Strangely patched CoCo 1

[Robert Gault]

I think there is a good chance it is the part described in the Tandy Tech 
Bulletin CC:20. The part is 26-3003B logic board AX-7089 which has an 
SN74LS12 and SN74LS393. I don't have a schematic but if the above is your 
part, it is designed to correct a timing problem which caused a hardware 
crash after about 30 minutes of use. It was a heat related problem that 
could be corrected by adding heat sinks and drilling air holes in the case 
without the need of the kit.

Phill Harvey-Smith wrote:
> Hi all,
> 
> Just got a second CoCo 1 off ebay (26-3002) and it has a strange little 
> patch board inside that my other does not (26-3004). The board is 
> mounted upside down next to the SAM, and has about 5 or 6 wires going to 
> various places on the CoCo board. Also one of the other chips, has had a 
> couple of it's legs lifted and a disc cap & inductor soldered to them.
> 
> I know these where factory fitted because the waranty seal had not been 
> broken.
> 
> I am in the UK, and this is a UK machine, the one thing that did cross 
> my mind that perhaps the mainboard is a US/NTSC, and the patches have 
> been made to convert the machine to run on the UK/PAL system.
> 
> Can anyone comfirm this and does anyone have a schematic for it ?
> 
> Cheers,
> 
> Phill.
>