Path: utzoo!utgpu!jarvis.csri.toronto.edu!cs.utexas.edu!usc!zaphod.mps.ohio-state.edu!sol.ctr.columbia.edu!lll-winken!lll-lcc!rzh
From: rzh@lll-lcc.UUCP (Roger Hanscom)
Newsgroups: comp.sys.ibm.pc
Subject: Keyboard Failure
Keywords: keyboard, V20, 4.8/10 MHz
Message-ID: <2759@lll-lcc.UUCP>
Date: 21 Feb 90 16:30:11 GMT
Organization: Lawrence Livermore Labs, LCC, Livermore Ca
Lines: 20

My clone died Monday with a "keyboard failure" message from the BIOS
prior to the memory check before booting.  This is an XT 4.77/10 MHz
(unamed) clone that I stuck a V20 in.  It is the second time that a
clone like this one has croaked with the same symptoms.  The first
time I bought a new motherboard and everything was fine.  I'd like to
fix both of these guys.  Anybody seen this failure mode before??  Any
ideas where to look??
The keyboard has 5 lines going to it.  There is +5v and ground (yes, the
5v seems to be there!).  There is an (output) from the motherboard --
a 7407 that seems to be logic 1 (5v) all the time, and an input that
goes to a shift register (LS322) that probably does serial in/parallel
out to the 8255.  The last line looks like it goes from? (looks like an
output) an 8-bit buffer (LS244) to the keyboard -- perhaps some hand-
shake??  Not having a schematic or knowing what a live P.C. looks like
makes this difficult.
I know, I know....I should just go out and buy a Mylex 386 @:^), but this
bugs me!  Any help out there???

              roger                 rzh@lll-lcc.llnl.gov