22 Mar
1998
22 Mar
'98
10:15 a.m.
On Sun, 22 Mar 1998, Doug Spence wrote:
Well, I've repeated what I did the other night. I plugged the Kaypro II
into the Kaypro 2's drives, and vice versa. Just the ribbon cable, not
the power. Whichever machine was plugged into the Kaypro II's drives was
able to boot, the machine plugged into the 2's drives just sits there with
the bootup message and eventually beeps and says "I cannot read your disk"
(or similar).
Interesting! Take a look at the back side of the II's drives and see if
you can identify the small black 'cable' that leads to the head. It will
move as the heads move. Anyway, if you spot two, then the machine has
double sided drives and that could be the reason that the 2's drives -
single sided - cannot read the disk.
I tried swapping the II's 81-149C with the 2's
81-232. Neither will work
with the other's ROM. The machines light both drive lights and fill their
screens with garbage characters (many of which are flashing). I even
tried swapping BOTH the boot ROMs and the character generator ROMs
together, in case they depend on one another, but got the same symptoms.
So the ROMs aren't even compatible between machines.
I looked at the other chips in the vicinity of the ROMs, and all part
numbers matched. And there are no obvious differences between the
motherboards except for that wired-up chip I mentioned in the II.
Very odd.
Obviously I didn't follow all of the traces on the motherboards to see if
they matched. :)
If you compare the part numbers on the motherboards - assuming that they
are there - you will find that the board on the II is an 81-110, whereas
the 2 should be either 81-184 or 240. They are not the same board.
Anyway, the only other thing I could try is to make
drive B in the 2 think
that it's drive A, to see if I can boot from there. Does anyone know how
these drives decide which one's A and which one is B? And can I switch
their identities without removing the drives from the metal housing? I
don't have the proper screwdriver to remove the drives.
This is usually set by a socketed DIP jumper plug on the drive circuit
board located near the ribbon cable connector. It could be a DIP switch,
but not usually. If the DIP jumper plug and they are both in the same
position, just swap them. If they are in different positions, then swap
the positions on both drives. These DIP jumper plugs have a frangible
strap between opposing pins, and usually all but one or two are broken.
- don
Doug Spence
ds_spenc(a)alcor.concordia.ca
donm(a)cts.com
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Don Maslin - Keeper of the Dina-SIG CP/M System Disk Archives
Chairman, Dina-SIG of the San Diego Computer Society
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