Am 7 Oct 2005 0:09 meinte Pete Turnbull:
As some of you know, I'm helping with an
exhibition of classic machines
in the Department of Computer Science -- for Open Day tomorrow
(Friday), and running conducted tours on Wednesday as well.
That's unusual, standard procedure is that a machine dies at
the opening day at the first real presentation - no matter
how often you testet before.
Well, one of the supposedly-working exhibits is my
KIM-1, but it died
this afternoon. I can't get it to do more than occasionally display a
single zero, on the leftmost 7-segment display. A cursory look with a
logic probe (and no docs to hand) shows the clock is running and at
least a few address lines are too. I bet it's a memory fault.
Not necersarry. Memory faults are rather rare on KIMS (in fact,
I never had one). First I'd look for dirt at the connectors and
arround the LED drivers, since a shortcut there might just screw
everything ... I found more than one KIM where the one or more
of the port lines where fried.
What are the common faults? I'm hoping it's
one of the 2102 RAMs,
because I stand a chance of having a suitable replacement. However, I
fear it's more likely a 6530, and I assume they're unobtanium. Has
anyone ever come up with a kludge to effectively use a 6532 (and are
they any easier to find?) with an EPROM? Or anything else?
No, not made of unobtainium, KIMs are still common, just the
process of separation is rather painful :) If it's one of the
6532, a replacement needs to be build. First thing would be
to connect a logic analyzer to see if the CPU is still running
a programm in ROM or not. If yes, all you need is either to
replace the internal RAM or the I/O Ports of the 6530. If you
have to hurry, adding a 6530 via a piggy pack PCB might be a
doable way - or put both onto a PCB. if there's more time,
I'd go ahead and put the I/O Part of the 6530 into a CPLD,
unsolder the 6530, bend the I/O pins below the chip (maybe
add also some insulator) and glue and wire the CPLD onto the
back of the board. Perfect disguise, as long as nobody turns
the board arround.
Same way if the ROM is fried (extrem unlikely): just add a
some (SMD) EPROM (1K used) onto the back.
Hans
--
VCF Europa 7.0 am 29/30.April und 01.Mai 2006 in Muenchen
http://www.vcfe.org/