[Coco] Primer on burning EPROMS?

[Rogelio Perea]

On Mon Jan 26 2015, Christopher Barnett Fox wrote:

Wanted to try burning some EPROMs, so bought one of the inexpensive Chinese
> TL866CS universal programmers off eBay, $39.99 shipped. Is there a primer
> anywhere on what else I'll need hardware-wise (e.g., a good source for
> compatible EPROMs, suitable cartridge interface, etc.), and information on
> how to actually burn and test?
>
> For cartridge interface, I have an FD-501, an FD-502, and a Disto Mini
> Controller 1.
>

The main thing while working with the CoCo is that all disk controllers
from Tandy prior to the FD-502 have a 24 pin socket for the ROM, the chips
that Tandy used are hard to find and if found, the programmer you have (and
many other modern ones) will have a hard time working with those chips -
bottom line you need to work with a 2764 28 pin EPROM, you can get those at
Jameco (where I recently bought a couple for my ADOS explorations), other
vendors should have them as well (Mouser, Digikey, Ebay).

The 2764 can be fitted into a 24 pin socket provided you run a couple of
jumpers and modify a couple of traces on the controller board (from the
earliest CoCo disk controller up to the FD-501); I do not have a Disto Mini
Controller but I assume it already comes ready for a 28 pin ROM, your 2764
should just be a drop in install.

The 28 pin to 24 pin adapter you can find info on the web on how to do it,
there is an outlet that sells a ready made adapters although these are
built in such a way that when placed on the disk controller you won't be
able to close the case - the whole setup grows beyond the maximum allowable
height inside the closed controller shell. Cloud 9 used to sell low profile
adapters, check with them for availability.

Last but not least, hopefully you bought an EPROM eraser. You will need
one! :-)


-- RP