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From: mason@unify.uucp (Mark Mason)
Newsgroups: sci.electronics
Subject: Fixing an old PC.
Message-ID: <6746fbq@unify.uucp>
Date: 5 Apr 90 19:25:21 GMT
Reply-To: mason@unify.UUCP ()
Distribution: usa
Organization: Unify Corporation, Sacramento, CA, USA
Lines: 37


Hello,
I just got ahold of an old IBM PC (real IBM), and keyboard input does
not seem to work. I have tried all of the real simple stuff (keyboard
and cable work fine on another machine, connector->mother board
connections are good according to my ohmmeter, tried a lot of
wiggling, etc).

When power is turned on, the following occurres:
"301" is printed in the upper left corner of the screen.
memory is checked (passes, god is it slow!)
floppy drive is accessed for a moment (reset?)
beeps twice
"ERROR. (RESUME = F1 key)" is displayed

Hitting F1 (or any other key) does nothing. (even caps lock does not
cause the light to turn on). The keyboard does seem to get power (the
keyboard lights all flashed sometime earlier in the boot process).

Any ideas?

I have a lot of replacement chips on hand, what I don't have at the
moment is an oscilloscope or a logic probe (thinking about getting the
latter), and I don't want to go replacing chips blindly. I do suspect
the 'ls322 shift register and the interval timer (a hunch), but I
wanted to wait for some feedback before doing anything rash (none of
these guys are in sockets...).

I would appreciate any advice on how to fix this beast.

Thanks alot,
Mark Mason
tektronix!pyramid!unify!mason
-- 
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