Teac FD-235GF 3156-u replacement

That could just be a standard PC floppy drive. Teac FD-235's are/used to be used in IBM compatible PC's. I'm sure I have some kicking around. I'll have a look on Monday when I get into work.

Hi Baron, the PC drives are FD-235 HF not GF as far as I've been able to identify and the jumper set is different.

For the most part I reckon all I need is to know the jumper matrix settings, from there I should be able to sort out modifying any current drive to suit.

However, if you do find some GF drives I would be most interested.

Thanks for the help Greg

Hi Baron, the PC drives are FD-235 HF not GF as far as I've been able to identify and the jumper set is different.

For the most part I reckon all I need is to know the jumper matrix settings, from there I should be able to sort out modifying any current drive to suit.

However, if you do find some GF drives I would be most interested.

Thanks for the help Greg

Larry

Hi Larry, thanks for the links - unfortunately not much use I'm afraid. I hadn't seen that pdf on the teac site but as it was about HG to HF differences no mention of the GF drive.

I'm particularly looking for the GF drive not the HF drive. The jumper pad on this drive allows for all sorts of non standard pinout configurations such as density select on pin 6 rather than 2 etc. The problem is some of these interfaces have changed over time, for example the density select can be either an input or an output or both depending on the drive and the controller and without the jumper data I'm not sure how the drive is actually configured to operate.

The controller on the drive is a T4A34F, again no luck in finding any info on this chip to allow me to identify what pin goes to what jumper. If anyone has a datasheet on that teac IC that would also be of some use.

Thanks Greg

You might want to pose this question to the floppy hardware gurus at "Individual Computers."

They make a product called the "Catweasel" which reads all floppy formats known to man. as such, they proabably have some experience with drives.

Or Tim Mann is also a floppy guru.

Hi Baron, no problems. Thanks for looking though. I've had some success using a standard pc drive. Had to use DS0 rather than DS1 (expected) and needed to ensure the drive was using disk change on pin

1. The only thing that is still a little peculiar is the density select and whether it's an input/output or both. Using a standard PC drive I need to use a HD disk but cover over the HD hole and that seems to work reliably. On the original drive I would use HD without covering up the hole. The only issues I end up with is that the drive light is always 1/2 on when not in use.

I'll keep looking for FD-235GF data and playing around. i'ts almost sorted now

Thanks Greg

On Tue, 24 Feb 2009 17:43:49 +1100, "gcd" put finger to keyboard and composed:

This URL suggests that pin 2 is an input to the drive:

I suggest you look at the datasheet for an old multi-IO chip such as were used on 486 and Pentium motherboards, before the functions were incorporated into the chipset.

For example, here is the datasheet for a Winbond W83757F:

Amongst the FDC pins is RWC, Reduced Write Current. "This signal can be used on two-speed disk drives to select the transfer rate."

Logic 0 = 250 Kb/s Logic 1 = 500 Kb/s

It is described as an "open-drain output pin with 24 mA sink capability".

I've seen this pin used in 2-speed 5.25" drives, but not in 3.5" drives. It could be that the HD hole in the diskette tells the [PC] drive what write current to use, but the drive does not report the diskette type to the controller.

Does your Advantest network analyser write 1.44MB or 720KB of data to the diskettes? It would seem odd if the drive were writing to the diskette as if it were a 720KB lo-den type while the controller were transferring data at a hi-den (500 Kb/s) rate.

Could it be that your current setup is operating at a 250Kb/s data rate, and that your diskette's capacity is being reduced to 720KB? Could it be that the original FDD uses the "RWC" pin as an output rather than an input, and that it communicates the diskette type to the analyser, in which case the analyser could automatically adjust the data rate to suit??? In the latter case, if the analyser doesn't get any feedback from the drive, perhaps it defaults to a lo-den data rate. You might like to experiment with a pull-down or pullup resistor on this pin.

- Franc Zabkar

On Sun, 22 Feb 2009 14:23:57 +1100, "gcd" put finger to keyboard and composed:

FWIW, this document refers to FD55-GFR 5.25" drives:

There is an LG strap and an I strap that define how the drive behaves in lo-den and hi-den modes.

- Franc Zabkar

On Wed, 25 Feb 2009 08:48:06 +1100, Franc Zabkar put finger to keyboard and composed:

There is also an In-Use (IU) jumper set that defines the conditions under which the in-use LED turns on. The standard jumpering for a PC AT system is to illuminate the LED whenever Drive Select is active, whether or not the drive is actually doing anything. Is it possible that the controller is constantly checking the DiskChange pin and thereby activating the LED?

- Franc Zabkar

Hi again Franc, I've been across all the jumpers on the drive I'm playing with and none appear to affect the dim led. it goes off but I'll keep playing around if I can't find the info I'm after

Cheers Greg

Hi Franc, yes - pin 2 determines the density of the drive which is usally related to the speed of the drive. Some fdc chips expect this to be sent to the dhip from the drive, some expect to send it out to the drive and others are bi-directional. Just depends on the age of the drive and the controller, as things changed from shugart to pc format interface.

This is why I'd like to get the jumper info - it would tell all.

I've had a bit of play with pull ups with no luck but I'll persist :)

Thanks for the links and suggestions, mind you, if all I end up with is a light 1/2 on I can live with that - just need to ensure the configuration i end up with is reliable in terms of data storage

Greg

gcd Inscribed thus:

DS1 (Drive Select) was the result of some bright spark realising that a twist in the cable could be used to determine which drive was "A" In practice it probably saved a lot of money for the manufacturers and confused techies !

It sticks in my mind that it was always an output in the sense that it was used to detect the difference between 720/144 Mb disks and set the rotational speed, 300/360 rpm I belive.

I wonder if that is anything to do with difference in the material used for the magnetic coating.