I think you're best off asking this question on the tech tangents discord.
The link for that can be found in the description of the video which link you posted.

since this is a very passive device I would verify all the connections again,
including the connections to the switch and make sure that the switch is actually switching properly.

It's fairly easy to make a switch for multiple drives all you need to move are drive select and motor on (assuming a PC)
I've done this a few times using a two-pin header and movable two-pin selection - just move it to the drive you want to activate.

If you want an actual front-panel switch, you can change drive B between two physical drives with a simple DPDT toggle.

Be aware that BIOS and whatever OS you are running can't auto-detect all drive types. so you will have to reconfigure the drive in BIOS when you change it.

Unless - you are doing this for an ImageDisk system - IMD talks to the drive directly and doesn't care what BIOS thinks it is (IMD can read lots of non-PC formats which are not supported in BIOS or PC OSs - In my main IMD system, I have drive B which is changeable set to NONE in BIOS)

Another option which might work for you.

On one of my IMD systems which happens to be built on a wooden board (so all exposed), I've modified the floppy to put the "twist" around the center connector - this makes drive A: at the center, and B: At the end - i just have the floppy cable (and switched power) coming out and it has both 5.25" and 3.5" connectors on it, so I can just attach whatever type of drive I want.

(I also made a 5.25" to 8" drive connector adapter - so I can also plug 8" drives onto it - And there is a "add 12v" option in my switchbox so I can provide (and switch) the 24v needed by 8" drives)

Re: Retro Rig Photo Thread

weedeewee wrote on 2025-11-16, 21:05:

since this is a very passive device I would verify all the connections again,
including the connections to the switch and make sure that the switch is actually switching properly.

If I change the type of drive in the BIOS, then that drive works fine, independently of in what slot of the switch board it is, and provided that the switch is selecting it. That means that all the connections are fine. The problem is with the drive that is not defined in the BIOS. Whichever happens to be. I think that doesn't work is DRIVER.SYS. The message "External drive is unit D" appears when MSDOS is loading, and if I try to access unit D: after flipping the switch, it attempts to read the correct drive, but it returns a fail message. Needless to say that the third drive, the one not defined in the BIOS, is correctly defined in CONFIG.SYS, but for some reason it doesn't work. I'm using MSDOS 6.22 and the DRIVER.SYS from MSDOS 6.22, but it seems as if DRIVER.SYS doesn't tell MSDOS what type of drive unit D is.

If I change the drive every time in the BIOS, and I switch to the correct drive, either drive works, though I'm not able to use both in that session. If I one to use the other, I need to reset, change the BIOS and boot.

popcalent wrote on 2025-11-17, 02:02:

, but for some reason it doesn't work. I'm using MSDOS 6.22 and the DRIVER.SYS from MSDOS 6.22, but it seems as if DRIVER.SYS doesn't tell MSDOS what type of drive unit D is.

I think any system information program will be able to tell you what drive type the drives are configured for. you might want to look into that.

as an extra test, try not using the techtangent adapter, just use two floppy drives as they were intended, drive A & B.
Leave the config.sys entry for driver.sys, and verify that the driveletter, set up by driver.sys,
works by reading an appropriate floppy from the disk drive which is being referred by the driver.sys set up driveletter.

weedeewee wrote on 2025-11-17, 05:50:

I think any system information program will be able to tell you what drive type the drives are configured for. you might want to […]
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popcalent wrote on 2025-11-17, 02:02:

, but for some reason it doesn't work. I'm using MSDOS 6.22 and the DRIVER.SYS from MSDOS 6.22, but it seems as if DRIVER.SYS doesn't tell MSDOS what type of drive unit D is.

I think any system information program will be able to tell you what drive type the drives are configured for. you might want to look into that.

as an extra test, try not using the techtangent adapter, just use two floppy drives as they were intended, drive A & B.
Leave the config.sys entry for driver.sys, and verify that the driveletter, set up by driver.sys,
works by reading an appropriate floppy from the disk drive which is being referred by the driver.sys set up driveletter.

Alright, I'll try this next!