Tip for next time: check the pinouts of a connector first, saves asking unnecessary questions:
http://old.pinouts.ru/HD/InternalDisk_pinout.shtml

Note: All Odd Numbered Pins Are GROUND see text […]
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Note: All Odd Numbered Pins Are GROUND see text

Pin Name Dir Description
2 /REDWC --> Density Select
4 n/c Reserved
6 n/c Reserved
8 /INDEX <-- Index
10 /MOTEA --> Motor Enable A
12 /DRVSB --> Drive Sel B
14 /DRVSA --> Drive Sel A
16 /MOTEB --> Motor Enable B
18 /DIR --> Direction
20 /STEP --> Step
22 /WDATE --> Write Data
24 /WGATE --> Floppy Write Enable
26 /TRK00 <-- Track 0
28 /WPT <-- Write Protect
30 /RDATA <-- Read Data
32 /SIDE1 --> Head Select
34 /DSKCHG <-- Disk Change/ReadyPin Name Dir Description

You're missing pins 4 (NC), 5 (GND) and 6 (NC). NC means not connected, and you can live with only 16 GND lines.

I have a floppy drive at home that is missing something like 8 pins. It didn't work in a 386, I haven't tested it in a more modern machine but it came out like that. Weird.

dionb wrote:

Tip for next time: check the pinouts of a connector first, saves asking unnecessary questions: http://old.pinouts.ru/HD/Internal […]
Show full quote

Tip for next time: check the pinouts of a connector first, saves asking unnecessary questions:
http://old.pinouts.ru/HD/InternalDisk_pinout.shtml

Note: All Odd Numbered Pins Are GROUND see text […]
Show full quote

Note: All Odd Numbered Pins Are GROUND see text

Pin Name Dir Description
2 /REDWC --> Density Select
4 n/c Reserved
6 n/c Reserved
8 /INDEX <-- Index
10 /MOTEA --> Motor Enable A
12 /DRVSB --> Drive Sel B
14 /DRVSA --> Drive Sel A
16 /MOTEB --> Motor Enable B
18 /DIR --> Direction
20 /STEP --> Step
22 /WDATE --> Write Data
24 /WGATE --> Floppy Write Enable
26 /TRK00 <-- Track 0
28 /WPT <-- Write Protect
30 /RDATA <-- Read Data
32 /SIDE1 --> Head Select
34 /DSKCHG <-- Disk Change/ReadyPin Name Dir Description

You're missing pins 4 (NC), 5 (GND) and 6 (NC). NC means not connected, and you can live with only 16 GND lines.

Dear dionb. I thank you for your reply. I am glad that you gave me a useful information although my question bothers you so much, that you need to take care that I won't ask again in similar ways. Well I could accept your opinion, that my question could be unnecessary. But it is not. Your answer helped me a lot. Also I had a certain motivation to ask such a question. You might think, that I was sitting on my hands and waiting for others to do the work. That's not my way. I always try to solve problems on my own parallel to asking such questions. You even might not know about my motivation. That's ok. I will explain it to you. I wasn't sure about how to read a scheme like the one you posted. But I can assure you, that I already googled for such a scheme. So I thought I will ask the vogons community. There will be for sure someone who can help me understanding what I found by myself. And so it was. Now that you explained the meanings of missing pins I feel relieved because I don't have to trouble about exchange of the Mainboard. Again: thank you and sorry for the lack of information about why I asked that question. Hope you understand it better now. I will try to point out more details of my own research in future questions.