VOGONS


First post, by Erwin_Br

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Hi all, I recently acquired a TEAC FD-55GFR-541-U floppy drive. It is detected, it boots fine (motor is moving) but it refuses to read anything. I’m trying to use it in my WIP build, a 486DX2. I cleaned the heads, checked the jumpers to the best of my ability. Currently the jumpers are set on D1, DC2 and FG.

Any clue what else I can check?

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Reply 1 of 9, by snufkin

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Might need the 'I' jumper closed as well.

From the manual https://deramp.com/downloads/floppy_drives/te … %20FD-55GFR.pdf:

(8) I/II/IS straps […]
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(8) I/II/IS straps

(a) Straps to select the speed mode of the FDD.

(b) When the I strap is on-state, the dual speed mode is designated. Disk rotational speed is switched between 360rpm for the high density mode and 300rpm for the normal density mode according to the HIGH/NORMAL DENSITY signal. Also the ready state is reset once synchronizing with the HIGH/NORMAL DENSITY signal. Refer to item 1-8-3 (13-l).

(c) When the II strap is on-state, the single speed mode is designated. Disk rotation speed is fixed to 360rpm independent of the HIGH/NORMAL DENSITY signal.

(d) When the IS strap is-on-state, the dual speed mode is selected like item (b). Eowever, the FDD maintains the ready state with no relation to the HIGH/NORMAL DENSITY signal . .

(e) One of the I/II/IS straps should be set to on-state.

[ah, just saw in your photo that II is connected, so that should be ok]

Reply 2 of 9, by Erwin_Br

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I used Dave Dunfield's ImageDisk and I found out the drive is out of alignment. A big bummer, because I'm unsure how to solve it. I have seen that I can unscrew the stepper motor, which is held by screws in oval-shaped holes which give me some room to reseat the motor. I'm going to give that a try, but to be honest I don't really know what I'm doing.

Reply 3 of 9, by Deunan

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Erwin_Br wrote on 2021-04-24, 15:26:

I used Dave Dunfield's ImageDisk and I found out the drive is out of alignment.

You can use IMD to kinda get it working - if you are patient enough - but that's about it. Doing it properly requires a scope, and a special aligment disk and these are unobtainium. I use floppies with original software - preferably something well known , that was made in many copies. It's cheaper to buy and was made on duplicating machines with pretty good aligment, which was often tested and corrected. You need a floppy like that plus a good scope, and a lot of patience - every 0.1mm makes a difference. IMD is only used to step the heads and verify I'm on right track, the actual alignment is done by peaking the signal on the scope.

If someone was stupid enough, or desperate enough during cleaning/restoration, to unscrew the upper head from the lower one, then you need to do head 0 (lower) first, then head 1 (upper), and let me just say it requires even more patience to do that properly (and steady hands). Then there's subtle things like correct head azimuth and/or making sure the stepper motor is not slightly twisted, or it might read some tracks but not others. Let's just say there is no easy way to do this other than trying as many times as it takes. But it can be done (took me some 2h to fully re-align a Shugart 455 yesterday).

Not sure about 55GFR but 55BR is a very impressive drive that reads floppies that other drives won't (and I re-aligned that one too so it's not like it's better because of factory settings), so don't give up on that TEAC. It's a great family of drives. Don't trash it please.

Reply 4 of 9, by Erwin_Br

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I used a MS DOS installation floppy as my “guide” and after some tinkering I got it to read OK in ImageDisk. I was also able to write an image of the disk as you can see. Unfortunately I’m still getting “Drive not ready” when I try to access it from DOS itself though. I’m getting pretty desperate. Maybe it’s the jumper settings, even though I already spent hours checking those 🙁

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Reply 5 of 9, by Deunan

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Erwin_Br wrote on 2021-04-24, 23:15:

I used a MS DOS installation floppy as my “guide” and after some tinkering I got it to read OK in ImageDisk.

I was once happy too with such result, before I got the scope hooked up and realized how far from optimal position the heads were still. Well, if you care mostly about reading and it works, you can just keep it like that. But any floppies formatted or written on that drive might not be readable on other ones, or with problems, and this will only get worse with time (as the magnetic fields slowly degrade).

As for the DOS problem, if IMD works then you have jumper issues. The 500 series are different from my 100 but, based on my experience with other drives, I would start by adding a jumper on RY - see if that works.

Reply 6 of 9, by kdr

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Erwin_Br wrote on 2021-04-24, 23:15:

Unfortunately I’m still getting “Drive not ready” when I try to access it from DOS itself though. I’m getting pretty desperate. Maybe it’s the jumper settings, even though I already spent hours checking those 🙁

I have an FD-55GFR 142-U installed in one of my turbo XT machines (as the B: drive) so I pulled it out and took a photo of the jumper settings. It's a slightly different logic board and layout as compared to your drive unfortunately. I've never met a more inscrutable set of configuration jumpers, like in some places there are horizontal and vertical labels that share the same pins -- WTF?!

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If you're getting "drive not ready", maybe you can try mucking around with the jumper labelled "RY"? I believe there are two ways the drive can report its ready status to the controller, and only one of them will work in an IBM PC compatible.

Reply 7 of 9, by Deunan

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Your drive is 100 series, like mine, it's a newer model - single chip design and non-removable 1k pull-up/terminator pack.

There should be a Disk Change signal (instead of Ready) prestented on pin 34 but on most systems even Ready will work, except OS will not notice when the floppy was swapped. But now I notice there is something of the sort on the 500 as well, to the side. 4 of them in fact, just one populated, and closed. So don't close RY unless you remove the jumper from what should be DC2? Can't see the text there. But DC2 should be a much better fit for PC than RY.

So, why doesn't it work - Erwin_Br, did you made sure the track 0 is actually the first one the heads see when the light sensor is hit? Can you post a screenshot of the IMD alignment function running with that DOS floppy in drive?

Reply 8 of 9, by Erwin_Br

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Deunan wrote on 2021-04-25, 00:01:

Your drive is 100 series, like mine, it's a newer model - single chip design and non-removable 1k pull-up/terminator pack.

There should be a Disk Change signal (instead of Ready) prestented on pin 34 but on most systems even Ready will work, except OS will not notice when the floppy was swapped. But now I notice there is something of the sort on the 500 as well, to the side. 4 of them in fact, just one populated, and closed. So don't close RY unless you remove the jumper from what should be DC2? Can't see the text there. But DC2 should be a much better fit for PC than RY.

So, why doesn't it work - Erwin_Br, did you made sure the track 0 is actually the first one the heads see when the light sensor is hit? Can you post a screenshot of the IMD alignment function running with that DOS floppy in drive?

My model does not have a place for a DC jumper, only a DC2. Now, apparently that means DISK CHANGE output on Pin 2 which I found out just now by explicitly searching for "DC2" because it started to dawn on me it might be the culprit. (None of the guides I've seen so far has shown this info, they always referred to DC)

During my attempts, I have been switching between DC2 and RY (and even both jumpered!), but it never occurred to me to remove both which I just did. And lo and behold: It worked!

Thanks for pushing me into the right direction, I really appreciate it!

Reply 9 of 9, by Deunan

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I guess you learn something new every day. It's the first time I see Disk Change output on pin 2, but sure enough I also found a mention of that now - and it looks to be TEAC specific. So in that case this my guess of how it works:

DC2: closed, RY: open - Disk Change on pin 2, nothing on pin 34
DC2: closed, RY: closed - Disk Change on pin 2, Ready on pin 34
DC2: open, RY: open - Disk Change on pin 34 (nothing on pin 2 or it could be 300/360 RPM switch or density input/output now - not used by PCs)
DC2: open, RY: closed - invalid combination (but will not cause any damage)

Seems like FD235HF model has jumpers marked as DC2, DC34 and RY34 - that makes more sense to call them that. I also wonder if BIOS makes certain assumptions about the drive signals after you set the type in settings, because I have some double-density (360k) drives that can only output Ready on pin 34 and yet every one of them works just fine with that.