keithe@teklabs.UUCP (Keith Ericson) (06/21/84)
It's too late for me, but I hope I can save someone else the
problems...
I picked up an Okidata Microline 80 for use on some work project
computers/controllers. It has a "Centronic-standard parallell
interface." To check it out I decided to connect it to my IBM PC. I
disconnected my Epson MX-80 and connected the Microline: the result was
*smoke* at both ends. The Microline supplies 23 volts (half-wave) to
pin 36 (via what used to be a 51-ohm resistor, I think) which promptly
fried a 7405 IC in the IBM, taking down the PC. Yes, there are
warning notices about the pins supplying power, but I mistakenly
assumed that this was part of the "standard Centronics interface." The
PC was relatively simple to fix - just replace the 7405. BUT - when the
7405 died, it turned around and (apparently) destroyed the 40-pin 8155
RAM-I/O-Timer IC in the printer. I say "apparently" because I haven't
gotten it working yet - the part is on order - and the strobe pin on
the Centronics connector seems to be shorted to ground, with the only
thing still connected being the 8155.
Anyway, like I said: I hope this will save someone else the headaches.
keith ericson at teklabs
P.S. I picked up the printer 'cause it's being cleared out for only
$135.