[Coco] J&M Controller schematic

[Stephen H. Fischer]

Hi,

Marty Goodman wrote:
> Dear Mark (Marlett),
>
> I have an Nth generation xerox of the schematic for the "JFD CoCo"
> controller from J&M.  This is a somewhat early model that used the now
> utterly unobtainable SY6591 controller chip.

When I visited them in Albuquerque and got the correct CC3 fix I was told
that either just before or just after the closing of Synertek that they had
purchased *all* the remaining stock of the SY6591. Good for me as they
tested my controller and remembered quickly that the minor problem I was
having could be fixed only by a new SY6591. Where those chips are now as you
suggest unknown.

> If this is of any help to you, let me know, and I can copy it and mail it
> to you.

I got a message that Mark found it on RTSI where I put it many years ago.

> J&M made a number of controllers in its day... some of them using 1773 28
> pin controller chips, others with that odd SY6591 chip.  (I believe they
> got some sort of a deal on that odd ball chip at the time they designed
> the controller that used it.)

I believe that they used the Synertek chip as it required only a 5 volt
supply, not the +12 -12? voltages that were required for others chips then.
Synertek chips were almost all ways better than Motorola. And a lower price
as you suggest. They had to be as they were a small company. I got SN 00001
of their adapter for the SYM to use the 6809 and ran Flex on it.

> I also have in my CoCo tech library (which I was considering getting rid
> of... know anyone who might want it?) schematics for a number of Radio
> Shack disk controllers (original, with pots, second generation, and at
> least one later generation model), and a HDS brand controller, a Disto
> controller, and that J&M controller, along with data sheets for the 1793
> and SY6591 controller chips (can't recall if I have data sheets on the
> Fujitsu controller chips that were drop in replacements for the Western
> Digital 40 pin models, except that they were 5 volt only operation, but I
> might).
>
> ---marty