Wow… what are the chances. Just a few days ago I finally figured out how to get that exact same model working. The issue turned out to be a missing jumper at UI — it needs to be placed horizontally, right above the DC jumper. Once I did that, the drive worked perfectly in two different machines (AT as B drive).

I am assuming this drive is being installed before the twist in the floppy cable.

The A: 3.5 floppy drive is most certainly hardwired as DS1 (most 3.5 drive are). And this would be an issue with this drive also being set to D1 (DS1 and D1 same thing).
Set it to D0 or D2 (most likely D2, as this tells the controller it is the drive AFTER the other drive one thus B:).

All the other jumpers are correct for AT/PC configuration.

The only thing I wonder about is RA1 which is the termination resistor pack, and there does not seem to be a jumper for it, and if is going to drive B: then the terminator generally has to be removed. So you may actually have to swap the drives, make this drive D0 put it after the twist and it will now be A:, and then stick the 3.5 before the twist and it becomes B: (3.5 drives auto enable/disable termination)

Your prior 5.25 was probably also D2 and not terminated.

Jumper on D1 looks correct, this will be B: if installed BEFORE the "twist" in the FD cable (cabe is straight/flat from drive to system)

LED lighting briefly is good ... not seeking is concerning (but depends on BIOS)

The -GFR is a HD (1.2m) drive. Is this supported on this system (wouldn't work on a PC or XT, must be AT+ compatible).

What type of drive did it replace? Did that drive seek at startup?

Normally AT+ does seek test at startup to tell 40 (DD) or 80 (HD) tracks on drive. This might not be done at all or can be disabled in some BIOS. Drive type in BIOS should be set to 5.25" HD.

A good way to test a drive is with ImageDisk (Align/Test function). If you have DOS (or WIn9x "restarted in DOS" - you can run it directly, otherwise having a working 3.5", you can use my floppy boot edition.

IMD talks to the drive directly (not through OS or BIOS), and will let you do everything the drive can do (Step, Format, Read, Write etc.) at a low level, which can help figure out exactly what is going on.

FWIW: Worth trying both with and without the terminating resistor pack. Technically one (and only one) should be present and installed at the far end of the cable (normally the A: drive) but I have found that in efforts to "simplify" things to the point of difficulty, many 3.5" drives can't select the termination ON or OFF, and therefore have less termination (to avoid too much when multiple drives are installed) - and I have run into cases where a 5.25" drive needed more (but I don't think this ever happened with a TEAC - good drives)

When in doubt, always best to install the termination, and position the drive at the end of the cable with no other drives installed - this is the original/official configuration and the one most guaranteed to work (but I have run onto a few floppy interfaces which could not drive standard 5.25" termination - there are a LOT of quality differences in this stuff)

Here is, how it work for me (sorry for taking this picture with it still assembled—I'm too lazy to take it apart). Same FDD, same combo 3,5" + 5,25", cable: MB - 3,5 connector (used) - 5,25 connector (free) - 3,5 (free) - 5,25 (used).
Floppy disk swap is set in the BIOS; in the OS, 3.5" is recognized as A and 5.25" as B.

Ydee wrote on 2026-07-10, 08:55:

Here is, how it work for me (sorry for taking this picture with it still assembled—I'm too lazy to take it apart). Same FDD, same combo 3,5" + 5,25", cable: MB - 3,5 connector (used) - 5,25 connector (free) - 3,5 (free) - 5,25 (used).
Floppy disk swap is set in the BIOS; in the OS, 3.5" is recognized as A and 5.25" as B.

Can't really see from your pics....

So the 5.25 is at the END of the cable (twist occurs between drive and system)
and the 3.5" is between twist and system
and you have "swap floppy" set in BIOS ? is this correct ?

This would make the 5.25" connected in hardware as A:, and the 3.5" connected in hardware as B:, then "swap floppy" should swap them to make the 3.5" A: and the 5.25" B:

This SHOULD work correctly - but it introduced some new variables and more reliance on "things working right"!

When solving a problem like this, it's ALWAYS best to simplify setup as much as possible.

I'd test one drive at a time, in the A: HARDWARE position (end of cable with twist between drive and system), no drive as B: with 'swap floppy" set OFF in BIOS. This is as close as you can get to an "original as shipped" system configuration and would eliminate some questions.

That should tell you if either (or both) drives work "as is" - then you can worry about refining it down to the actual setup you want, and identify where exactly problems are occuring.

Also -- you didn't answer my questions:
- What was the exact type of the 5.25" drive that was working (before you replaced it)
- Did it do the SEEK at powerup? (when it was working)

Hi Dave,
I bought the TEAC from a friend who had been using it in an old PC. I don't know what the configuration was, so I just plugged it into my PC, and without using "Swap FDD," there was some kind of problem in Windows 98 SE (I don't remember exactly what it was—maybe the FDD wasn't recognized at all, or maybe it was something else).
It works fine this way, and I’m not going to worry about it any further—it’s probably not exactly “the best,” but it reads and writes floppy disks, and that’s all I cared about.

I'm not TS, so he's the one who has to answer your questions.

Ok, my apologies for confusing the two of you.

Looking back through the read, it looks like the OP hasn't actually responded at all .. not knowing exactly what arrangements are in place, I've been kinda not paying attention to the author and just an giving information -- I had asked some things, then someone posted several pics saying this is how it is... I'll pay more attention to the actual author from now on.

OP again:
PC is a Pentium 166 non-MMX Compaq, so AT+ and has worked with a previous 5.25" floppy.

Current configuration on the cable is:
Motherboard ---- 5.25" (B:) ---/twist/--- 3.5" (A:)

The previous 5.25" floppy drive that was working is a Fujitsu M2553K-03B. It is jumpered as DS1 and has the "TM" termination jumper on. Which in the context of how it was setup seems wrong as it was in the middle of the cable, yet everything is working that way. The Fujitsu 5.25" floppy seeks on boot.

The only reason for swapping drives is that the Fujitsu is the wrong color for this case.

In this same cable arrangement, with the Teac set to D1, it is not detected by BIOS, does not seek at boot, but LED does briefly illuminated.

Same configuration but added the jumper IU horizontally as suggested - no change in behavior.
-----------

Now some tests with changing arrangements:

Removed 3.5" drive from the cable chain. Took IU jumper back out. Connected Teac as the only device on the very end of the cable (after twist), with jumper set to D0. When I start the PC in this configuration I get an error 601 - Diskette Controller Error. Same configuration but with D1, D2, or D3 selected - all result in no drive detected. LED light stays on the whole time.

Put the 3.5" back in. Motherboard ---- 5.25" (B:) ---/twist/--- 3.5" (A:)
Teac with D0, D1 , D2, or D3 - no 601 error, but 5.25 drive not detected; does not seek; A: drive still works.

I am not sure or clear about the terminating resistor situation on the Teac. But at the moment, no configuration I've tried makes this drive detect/work despite the LED briefly lighting in most of the configurations where it is in the B: cable position, or staying stuck on when it was on the A:

Something is quite wrong with the TEAC. First, always leave drive select jumper to the second option.. there is no reason to change it for PC.

In fact, I would keep all its jumpers the way they were from your friend (since it was working for him).

I advise testing the drive on another machine if you have one, just to rule out whether it is really drive config or simply incompatibility between that particular mobo and the drive (shouldn't be the case though on a Pentium 1 board).

wolfsburged wrote on 2026-07-11, 22:16:

... The previous 5.25" floppy drive that was working is a Fujitsu M2553K-03B. It is jumpered as DS1 and has the "TM" termination jumper on. Which in the context of how it was setup seems wrong as it was in the middle of the cable, yet everything is working that way. The Fujitsu 5.25" floppy seeks on boot.

Technically, termination should only be on the one drive at the far end of the cable. I have run into sustems/FDCs where a 3.5" at the end of the cable didn't fully terminate enough toe the interface on the 5.25 which had to remain ON - which is why I said "worth trying" - but thie is VERY rare!

Removed 3.5" drive from the cable chain. Took IU jumper back out. Connected Teac as the only device on the very end of the cable (after twist), with jumper set to D0.

BOTH drives on a PC (with has the twisted cabke) MUST be set to D1 - IBM thought users who were capable of adding a drive, might not be capable of moving a jumper - which is why the "twist" exists, it re-arranges signals so that the D0 select shows up in the D1 position after the twist (and is actually at the wrong "originak" place on the cable so that it can't work in a straight flat (non-twisted) cabke even if jumpered as D0!

To confirm that the drive works, best to configure it as the only drive in the system as A: (at end of cable (After-twist), jumpered as D1 and terminatiins ON.
(suggested tests may involve multiple powers ON/OFF cycles - I'd disconenect any HDs till after I'd figured thinds out)

On powerup: LED lighting briefly = good, always off = bad (not jumpered as D1) , always on = bad (usually indicates cable connected upside down, grounding all signals to the drive including select)

Get this configuration working with the knows good drive, and see if you can configure BIOS to cause it to seek at startup.

Then swap to new drive - if it doesn't do the same, it's either not configured correctly (check jumpers) or is defective.

If you want to debug further, we can get you setup with my ImageDisk tool (which can do some more comprehensive drive tests)