Found the explanation of the small circuit board in early and later Kaypros (TurboROM v3.4 Manual, appendix H, page H-4):
H.3. Early Kaypro 10 Upgrade 81-303, Explanation
The two versions of the small circuit board differ primarily in
how they generate the master reset signal for the hard disk
controller board. The early version connected the second floppy
disk drive select signal directly to the hard disk controller
master reset. The later version of the small circuit board uses
the inverted second floppy disk drive select line for connection
to the hard disk controller master reset.
The modification to the early version of the small circuit board
detailed in this appendix inserts an inverter into the master
reset logic for the hard disk controller. The addition of the
inverter makes the early board functionally equivalent to the
later version.
Note: The original Kaypro utilities PUTSYS.COM, PUTOVL.COM
and FMT305.COM, which were provided with the computer
should not be used after these modifications. If you
are inserting the Kaypro 81-302 ROM, replace these system
utilities with versions from a later model Kaypro 10. If
you are inserting the TurboROM, the utilities
TURBOGEN.COM and K10FMT.COM, provided on the TurboROM
Support Software Diskette, should be used.
The actual modification of the early board (TurboROM v3.4 Manual, Appendix H, page H-3):
5. Modify the Small Circuit Board
Make the following changes to the small circuit board.
Keep the wiring short and as neat as possible. The set
of 50 pins will be referred to as J1; the set of 40 pins will
be referred to as J2. On the solder side of the circuit
board, a square solder pad identifies pin 1 of each set of
pins. All pins in the row with pin 1 are the odd numbered
pins, all pins in the other row are even numbered pins. Refer
to Appendix E for basic information concerning the pin
numbering of IC's. Wires should be installed on the solder
side of the circuit board.
1. Cut the trace that runs from J1 pin 45 to J2 pin 39.
2. Cut the trace that runs from U1 pin 7 to U1 pin 2.
3. Add a wire from U1 pin 1 to J1 pin 45.
4. Add a wire from U1 pin 3 to J2 pin 39.
5. Add a wire from U1 pin 2 to U1 pin 14.
Ref: Plu-Perfect Systems Advent TurboROM V3.4 Manual (text version:
ftp://ftp.mrynet.com/operatingsystems/Kaypro/Private-Images/TROM-DOC/Turbo_Rom.txt )
From what a few of us here gathered, it looks like the KayPlus is looking for the early mid-board, and not the later one. It never releases the reset on the WD1002.
Also, historically speaking, the way we've adapted the 27(c)64 EPROMs to work in the K10/83 with 24-pin socket, was to tie pins 26,27,28,and 1 together, and then jumper from P2 on the 2764 to p2 on the Z80.