Bill:

8050:

Just proved the 4066 theory.  This chip caused a problem on one of my most reliable 
and long used 8250 Micropolis drives.  It had the RCA4066BE in it and I replaced 
it with a MC14066 from Motorola.  Works like a champ now.

D9090:

Here's a type in program you can save to change device numbers and is commonly 
called the Change Unit program.

odn = Old drive number
ndn= New drive number

Have floppy drive off and the 9090 on when you execute this.

10 open 15,odn,15
20 print#15, "m-w"chr$(12)chr$(0)chr$(2)chr$(ndn+32)chr$(ndn+64)
30 close 15

on the last two it would be chr$(41) and chr$(73) for changing to unit 9.

Regarding the best fix:

Open the unit (of course unplugged) from the back look all the way to the left 
rear for the 6532 with the circuit pads to cut.

We don't want to cut them as it will of course modify the board but the pins that 
control the unit number are 22,23,24.

Unit number    Pin    Pin    Pin

8                     0        0       0
9                     0        0       1
10                   0        1       0
11                   0        1       1
12                   1        0       0
13                   1        0       1
14                   1        1       0
15                   1        1       1

The 0's mean leave in the socket and the 1's mean gently bend away from the socked 
with a small needle nose.


-0--
 I don't recall if there ever was a separate 9060-9090 test.  
I believe the CBM test was the header command if I recall.

The header command uses a (for the time) sophisticated test of each track and sector 
and determines whether it's good or not.  If not, it marks it bad as with the old IBM type 
low level formats.  That's what I used and have trusted since the mid 80's.

Bruce

Hope that helps until you get the manual.