[Coco] RS-232 Pak problems

[Gene Heskett]

On Sunday 04 February 2018 12:48:22 Allen Huffman wrote:

> On Feb 3, 2018, at 11:19 PM, rietveld rietveld <rietveldh at hotmail.com> 
wrote:
> > MikeyTerm, GregETerm, and Ultimaterm all work with this pak using
> > RSDOS
> >
> > Xcom9 works with OS9
>
> For some reason, many of the RS-DOS programs are not making lights
> blink at all. I can toggle them to bitbanger and try though that cable
> and they work, but they aren’t seeing the Pak. Under OS-9 it does send
> data.
>
> It has been very curious. As much as I don’t want it to be my hardware
> dying, that wold explain a lot of this weirdness.

Memories are slowly percolating up thru the years here Allen. Is this 
rs232 pack equipt with that little tin plated box with an "Aztec" label 
on it? Thats a 5 volt to +- 12 volt convertor, and the failure rate was 
quite high as it ran hot. I have excised it from the pcb board, and 
jumpered its output islands to the appropriate pins on the card edge to 
connect them to the +- 12 volt pins the multipak furnishes.  So it will 
only work in a multipak, or a clone thereof, that supplies the +-12 
volts the pack needs.

The other high failure rate items are the mc1488/mc1489 chips, which are 
the voltage translation buffers from the ACIA's TTL logic levels to the 
+-12 volts  the bus needs. These seem to be quite static electricity 
sensitive as I've had to replace several of those over the years, 
sometimes more than once. There were at one time, probably 15-20 of them 
in use at the tv station back then.

-- 
Cheers, Gene Heskett
--
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