May 19 2021 Herb Johnson

In Feb 2021 I measured continuity on two sets of three 800K cables:

two "Apple 590-0167" as marked, red stripe
two "590-0437" paper lable, red stripe
two no marks or lables, yellow stripe

The cable paper-lable 590-0437, is continuous except pins 9 and 20.
The cable yellow no marks, is continuous except pins 9 and 20.
The cable 590-0167, is continuous ALL PINS.

pages below are from "Apple Service, Technical Procedures,
Macintosh Family, Volume One"

Mac. Plus parts-list page 7.7 rev Dec 91, says
part 590-0167 is "cable (red striped)", 
part 590-0437 is "cable (yellow striped)"

Mac Plus Additional Procedures page 6.9 rev May 90,
says quote 

There are three series of 800K drive mechanisms.
All three mechanisms can be used as an internal drive,
but only with the cable specified below. If you do not
use the correct cable, the drive will not work
correctly.

Series Number                       Cable Needed
MFD-51 W-03 (Red on Silver Label)     Yellow
MFD-51 W (Black on Silver Label)      Red
51W-I0 (Black on Silver Label)        Red

End quote. 

The Macintosh Computers Service Guide March 1991, has similar information
about drives versus cables by color, number and drive ID. 

"'Macintosh Repair & Upgrade Secrets'
Book by Larry Pina says pin 20 is speed control, and pin 9 is -12 V."
Regards Les VanDyne

May 2022

A customer has a Mac Lisa and needed a floppy drive. 
But they only had a working 800k "red labled" drive from another Mac,
and a red drive cable on the Lisa. The red drive did not work on the Lisa.
I explained the cabling, and that on the drive and computer board, the cable
connector had a mark for pin 1 for reference. The customer said:

"I checked for a mark on my original 400k drive [cable connector]. 
I found an arrow on the corner where you insert the cable.
Then I assumed it was pin 1. I matched with the 800k drive [to find pin 1 there.
I] removed pins 9 and 20 [from the 800k red-labled drive], 
[cabled it to the Lisa,] and it WORKS!"

If you choose to modify your 800K drive, I suggest you lable it 
"pins 9 and 20 removed" for future reference. - Herb Johnson