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.

Dear Sirs, I got the Floppy Disk Drive Samsung SFD-321B /LBL1 and it has only 22 pins and not 34. I have problems to recognize this drive. Do you know if this drive it is only specific of a computer brand?

jnemo2004 wrote on 2022-12-08, 19:52:

Dear Sirs, I got the Floppy Disk Drive Samsung SFD-321B /LBL1 and it has only 22 pins and not 34. I have problems to recognize this drive. Do you know if this drive it is only specific of a computer brand?

It's a standard 34 pin connector.
for some reason they just removed pins from the lineup,
likely because most or all of the removed pins are ground pins and were seen as superfluous,
yet the connector is a standard 34 pin connector in accordance with the standard floppy 34 pin connector.

edit: Just because it only has 22 pins does not imply it is a 22 pin connector. Those 22 pins are the ones available in a, for the rest of the pins, standard 34 pin connector layout.

OK. Thank you very much.

Might be worth mentioning the disaster known as keyed floppy connectors, where usually pin 3 is missing/filled in but sometimes it's 5, if there's a notch on the perimeter of the connector IDE style it might want to face up or down, and sometimes it's blatantly in the opposite direction of the matching notch on the PCB (examples: Olivetti PCS 286’s Sony drive, or the Starman's rant)!