please post photos of the underside of both drives connector pcb.

or use this for reference of jumpers. https://www.vogonswiki.com/images/2/28/Teac_F … R_underside.jpg

That's a modern TEAC on that photo, most have older guts and more jumpers. Anyway, my guess is both these drives are set to D0 instead of D1 (probably came from a machine with Shugart interface).

Just one Jumper. The green one, allready tried on and off, no difference at all.

I'll try to look info about this shugart interface.

Thanks folks.

Yours is a 55 FD-GFR-0xx . There are manuals for GFR-1xx , 3xx, 4xx, 5xx and GFR-7xx but not -0xx AFAIK. Let me check my archives...

added: Having "resistors" instead of true jumpers is a bit odd. I can say for a fact that if you are using this on a AT/286/386/etc that D1 should be jumpered, yours has D0.
That way the cable end floppy (after twist) is A, and the other is B drive. The U# ones are for LED response and if all off then for LED on with DC disk change and with DC being jumped. Yours has RY jumped.
My guess is they were not from a standard AT/PC but some OEM that needed things different for it's specific controller.

I was reading last night about those drives with your clues.
Hace to read the resistor value but maybe its a zero resistor... I'll solder a bridge on It and try again.
I guess D1 is the mode with NO preference, and let the cable decide the orden as you said
Thanks, I'll share my results.

Horun wrote on 2023-05-05, 23:44:

Yours is a 55 FD-GFR-0xx . There are manuals for GFR-1xx , 3xx, 4xx, 5xx and GFR-7xx but not -0xx AFAIK. Let me check my archiv […]
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Yours is a 55 FD-GFR-0xx . There are manuals for GFR-1xx , 3xx, 4xx, 5xx and GFR-7xx but not -0xx AFAIK. Let me check my archives...

added: Having "resistors" instead of true jumpers is a bit odd. I can say for a fact that if you are using this on a AT/286/386/etc that D1 should be jumpered, yours has D0.
That way the cable end floppy (after twist) is A, and the other is B drive. The U# ones are for LED response and if all off then for LED on with DC disk change and with DC being jumped. Yours has RY jumped.
My guess is they were not from a standard AT/PC but some OEM that needed things different for it's specific controller.

Maybe two PC88 drives?

I found a 051 Drive in a "japanese eBay" page. Now reading about those drives, and this page is a VERY interesting one.
https://www.leadedsolder.com/2018/09/02/pc88- … py-adapter.html
Those lines (crossing the Drive select and the motor on) would cause this weird responses...

Now I have to find out the Drive parameters, and if there's a way to use them on PC (with some kind of adapter?) Or even if its worth the effort.

while the jumpers haven't been soldered on to the pcb, the positions for them are clearly available.
D0 is even bridged by what looks to be a resistor, same goes for RY and HS and likely some others.
If the pins were soldered in you could have a field day trying out all the jumper configurations.
I guess you can figure out what to try next.

These drives are permanently jumpered to D0 and also with RDY instead of DC. So I'm pretty sure these came from Shugart bus - Atari ST maybe? I'm actually curious what machine used G* type TEACs that is not a PC...

To reconfigure those the resistors must be moved, or removed and pins for new jumpers soldered in. Well I suppose one could just use a piece of wire too (these resistors are probably 0 ohm or close to it) bu jumpers allow reverting back to original configuration more easily.

Game over.
http://bitsavers.informatik.uni-stuttgart.de/ … chure_Mar85.pdf
This brochure says those are 1Mb / 1,6Mb drives, and It means no PC compatibility.
What do you think?

You could find more info about TEAC units here;
http://bitsavers.informatik.uni-stuttgart.de/pdf/teac/

GFR are capable of switching speeds so can be used as QD rather than HD, which was most likely the mode they were used in whatever machine they came from. HD is mostly a PC format. But there is no reason they can't be reconfigured to HD or dual-speed operation - even if, and again that's probably the case, they are now semi-permanently set to QD via soldered resistors.

Don't let the numbers fool you, 1.0M is for QD and 1.6 is for HD but _unformatted_ capacity. F* TEACs are QD only and G* are HD only, GFs are switchable (by jumpers or extra signal on pin 2). R stands for revised I guess, TEAC introduced a major refresh of their 5.25" drive series in mid-80's (more integrated electronics, less power usage, some minor mechanical changes and simplifications).

Here is some Original docs found from Teac archives 1998 and 2001..
5004 FD 55 GFR-1xx and GFR-5xx (1.2Mbyte) series strap (jumper) definition
5005 Current 5.25 in FDD spec sheet FD-55GFR-7xxx
5006 FD 55 GFR-7xxx series installation guide
5007 FD 55 GFR-7xxx (1.2Mbyte) series strap (jumper) definition
and
5FD0050A FD 55GFR-340 440 540 (5.25" 1.2MB Floppy Disk Drive) Specifications and installation guide.
I had uploaded them here: http://www.vogonsdrivers.com/getfile.php?file … &menustate=28,0
also here is more info: https://retrocmp.de/fdd/teac/fd55_i.htm

Deunan wrote on 2023-05-06, 09:56:

These drives are permanently jumpered to D0 and also with RDY instead of DC. So I'm pretty sure these came from Shugart bus - Atari ST maybe? I'm actually curious what machine used G* type TEACs that is not a PC...

Agree !! Not from a standard PC. The same settings are used for the "Alpha Micro" S-100 systems irrc.

Thanks, I'll try to understand the configuration and specs.
Maybe there's a way to put this jumpers in the "right position" to get a compatible 1,2 Mb PC capable device.
This pdf sounds really good.
Maybe...
https://retrocmp.de/fdd/teac/TEAC_FD-55_Jumper-settings.pdf

IT WORKS!

I cut the zero resistors in RY and D0, and put jumpers in DC and D1. Then I managed to turn a PC8801 drive unit in a working lovely AT compatible one!

Strange behavior... More testing needed.

Thanks for the info.

DC signal is not properly detected.
I could read a floppy, then I swap the floppy and i only get the old FAT, then I reboot and same again, drive reads FAT for the first time and then no change detected. Just as described here: 3. DISK CHANGE / controller <<< disk https://retrocmp.de/fdd/general/floppy-bus.htm#pin34

Signal is going from 34 pin, to underneath the big chip, I think that I need some aditional jumper...

Ideas?

bing wrote on 2023-05-31, 17:03:

DC signal is not properly detected.

What did you set in the BIOS? Is the drive set to 1.2MB? Can you read entire HD floppy without any issues?
Try removing the I jumper (green on your photo), it shouldn't be required for PC operation - DC signal should work independently of speed settings but best to check.
Your other jumpes look like my GFR TEAC so I'm suprised it doesn't work... my drives were not dual speed from factory and do not have Q2 and Q3 transistors and the 3 resistors around them. I never bothered tracing the PCB to see what those do, but you can investigate if any of these transistors leads are connected to RDY or DC.

EDIT: Maybe this photo will help you.

Nice Deunan ! I noticed there are a few other changes yours has but bing's does not: FG jumped for frame ground.....
S1 and S4 no jumpers but that could have to do with the speed, no mention in the doc 504.pdf.

Thanks Deunan and Horun.

I did it!

Step by step:
- Yes, BIOS says it's a 1.2Mb unit
- the I jumper must be ON to get it working 300 rpm or 360 rpm (depending on the HD signal). Deunan, your drive works with HD floppies in DOS? It seems to be configured to get ALLWAYS 300 rpm, I'm a bit confused about it.
- The top left jumper it's not necesary in my unit, the Ov signal is attached to the frame by the 'R1 thing'.
- I coundn't find any information about S1 to S4, no idea about what are they for... but you were pretty close.

The first resistor you proposed to cut is not S1 (yes, S1 is far away from S2, just on the left of the 'black thing') is E2,

In retrocomp.de info you could find:

Set the E2 strap to the ON state only if your computer requires MASKING THE INDEX. (i.e. PC and older PC/XT that do not give the drive enough time to reach a ready state when the disk replaced.

I cut this resistor and BINGO! Everyting works!

The other problem was in my floppies, straight from the 80's, the only HD floppy (I guess) is not labeled and HANGS the computer as I try to read it. The DD ones work fine.

bing wrote on 2023-06-06, 11:23:

- the I jumper must be ON to get it working 300 rpm or 360 rpm (depending on the HD signal). Deunan, your drive works with HD floppies in DOS? It seems to be configured to get ALLWAYS 300 rpm, I'm a bit confused about it.

It's not a drive in active use but I'm pretty sure I run some tests in DOS on it before I packed it into a box. I don't like storing things in unknown condition (unless I have no easy way to test them). AFAIR the drive should default to permanent 360rpm, and the way it works is the PC floppy controller can do 250, 500 and also 300 kbps transfer rates. 300 is the value required to use at 360rpm to emulate 250 kbps at 300 rpm. DOS/BIOS should try all 3 when trying to read the floppy, at least the mobos I have do because I can hear the motor speed change when trying to read a newly inserted floppy on a drive with HD/speed signal enabled.

bing wrote on 2023-06-06, 11:23:

In retrocomp.de info you could find:

Set the E2 strap to the ON state only if your computer requires MASKING THE INDEX. (i.e. PC and older PC/XT that do not give the drive enough time to reach a ready state when the disk replaced.

Curious. I wonder why it doesn't work with masking enabled, is the delay too long and the drive/OS gives up too soon? Or is this somehow interfering with DC signal (since it's now DC and not RDY). Older DD drives didn't have DC at all and RDY wasn't really used on PC, there was usually just a software delay to give the motor some time to spin up and stabilize.

bing wrote on 2023-06-06, 11:23:

The other problem was in my floppies, straight from the 80's, the only HD floppy (I guess) is not labeled and HANGS the computer as I try to read it. The DD ones work fine.

Also a curious issue that hang. I wonder if the floppy has sectors that are not 512 bytes long and that somehow causes DMA to overwrite parts of DOS structure (buffer overflow). Or maybe you have some virus in the system, it's trying to infect the floppy but fails somehow.

Thanks for your thoughts.
I'm waiting to have some "New" floppies to test properly all this stuff.