[Ham-Mac] Mac Classic II Serial Port Kaput

[David Kelly]

On Sat, Apr 19, 2003 at 08:25:39PM -0400, Chris Smolinski wrote:
> 
> Or if you don't want to cram something into the already tight space 
> in the Mac, build an external buffer circuit that translates between 
> the RS422 and RS232 levels, which could also add protection.

I think for something like this there is lots of space. Just not much
space on the back for another connector so I suggested a ribbon which
cna be squeezed between the MB and other connectors hanging out the
back.


> >If you don't mind (5) 1.0uF capacitors then the MAX-232 is a popular
> >choice. One could even route a ribbon cable out the back with DB-9P in
> >PC-AT pinout.
> 
> The MAX233 is a bit cleaner in that you don't need 4 of the 5 caps, 
> since the charge pump caps are built in.

Once Upon A Time the MAX-232 was available at Radio Shack. Don't know
its current status. Others such as the MAX-233 are nice but 1.0 uF caps
are less expensive than the difference in price between the 232 and 233.

Not sure if anybody used Maxim RS-232 drivers on their clone PC serial
ports but it might be worth digging at local Mom & Pop PC Shops for junk
serial boards. If you find one, study the circuit and cut it off the
board with a saw rather than remove the chip. Remove the chip and the
capacitors. And maybe the connector as well.

-- 
David Kelly N4HHE, dkelly@hiwaay.net
=====================================================================
The human mind ordinarily operates at only ten percent of its
capacity -- the rest is overhead for the operating system.