21 Mar
1998
21 Mar
'98
6:18 p.m.
On Sat, 21 Mar 1998, Doug Spence wrote:
I finally opened up my Kaypros today to see if I could get the '2'
working. The II and the 2 seem to be almost identical inside, with two
notable differences: One of the ROMs has a different number on it, and
my Kaypro II has some wires soldered between pins on one of its chips.
The Kaypro II has a chip with a sticker marked "81-146A", with the
"A"
stamped on in read ink. The Kaypro 2 has a chip with "81-232" on it, in
the same location.
If the layout of the two boards seem identical, the chip in the II marked
"81-146A", which is the character generator ROM, is in the wrong location
(U47). It should be in U43. The one in U47 should be either "81-149" or
"81-232". They may have gotten swapped.
What are the differences?
The chips at position U87 on both motherboards are marked DM74LS390N, but
the one in the Kaypro II has been messed with. It's a 16-pin chip, and
pin 1 has been bent upward and a wire soldered onto it, which leads to pin
6. Pin 9 is missing. Pins 12 and 15 are attached with a wire.
Is this normal for a Kaypro II, or has someone made a modification?
It is a modification.
Anyway, I managed to make a copy of the WordStar disk
that came in the
drive of the II today, using my Amiga 1000, A1060 SideCar, A1020 5.25"
floppy drive, and TeleDisk. So now I have a disk that boots reliably
instead of 1 out of every 5-10 times. That meant that I now know there's
something wrong with the Kaypro 2, because it won't boot at all with the
new disk. Before, it may have just been a borderline disk that was
causing the problem.
Not necessarily. Unless both machines used the 81-232 boot ROM, there is
every chance that they both will not boot from the same bootable disk.
The boot ROM determines the revision of the operating system required.
So (tell me if this was a bad/dangerous thing to do) I
opened both
machines up and attached them to each others' disk drives. They were
plugged into a power bar, so I powered them up simultaneously with that.
The Kaypro 2 boot up with no problems, using the II's drives, and the II
was incapable of booting using the 2's drives, so I've got the problem
located to drive A of the Kaypro 2 now.
Maybe not. See above.
And BTW, both the II and the 2 have full-height
drives.
Both keyboards have missing keys (including broken plungers). Will this
be easy to fix?
The usual failure mode is for the cruciform projection on the switch
plunger to get broken off. You will need to unsolder the switch and
replace it with a good one. With the benefit of a solder sucker, it is
not necessary to remove the circuit board from the keyboard metal work.
I'm thinking of fixing the 2, and using the II for
parts, simply because I
like the colour of the 2's green phosphor monitor better (and some other
minor things). :) Is one model more rare than the other? IOW, does one
warrant saving more than the other? If not, I'll go with my feeling and
fix the 2 with parts from the II.
The 2 is probably less common.
Doug Spence
ds_spenc(a)alcor.concordia.ca
- don
donm(a)cts.com
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