View Full Version : Problem with FDD

April 22nd, 2006, 02:06 AM
I have 5.25" Siemens fdd from '82, it's 5,7 cm high. I don't know for what computer it was designed, but it work on my 386 but not correcty - it sometimes read disks and sometimes can't find sector or can copy/read only half disk. What can I do to get it back to work?

April 22nd, 2006, 03:58 AM
Maybe you're using the wrong disks format in the wrong drive?

Are the Disks you are using formatted in the mentioned drive?

Uually Cant Find Sector means a bad disk (I think) Formatting them again may help

April 22nd, 2006, 04:38 AM
I use DD disks. I've formated one in other drive and I copied files, it was full and Siemens copied it on disk correctly. When I format disk in Siemens it mark few bad sectors, but the same disk formatted in working drive has no bad sectors.

the xt guy
April 22nd, 2006, 05:52 PM
I have a listing of specs for floppy drives I found on the net.. There is only one Siemens on the list and it is listed as a 180K drive, full height.

Could that be it then, it is a single sided drive?

April 22nd, 2006, 11:31 PM
Yes, It's single sided. I think that electronic and head are good and problem is in mechanism. But there is not no way to recalibrate it...
http://img161.imageshack.us/img161/8817/fddgif4zn.th.gif (http://img161.imageshack.us/my.php?image=fddgif4zn.gif)

April 23rd, 2006, 12:00 AM
the dd disks may be the problem. Try finding some old single sided disks if you can.

April 23rd, 2006, 12:44 AM
Unable to write BOOT format terminated. Maybe I should put it on desk horizontal?

April 23rd, 2006, 07:14 AM
Single sided drives use double density diskettes. They just use one side of it. To use the other side of a double sided diskette, you'd have to flip it.

Double sided drives use the exact same media .. they just have the read/write heads on two sides instead of one.

Back in ancient times, machines came with single sided drives. I'm thinking Apple ][s and C-64s. You could actually buy single sided diskettes too, which just meant that the manufacturer only tested on side. If you 'notched' the diskette in the correct spot (where the write protect tab would go on the non-tested side), you could get away with using the other side.


The drive might need a thorough cleaning. Start with the rails that the head assembly moves along. Clean them thoroughly and then lubricate with something that is silicone or Teflon based. (I use a tube of 'Precision Oiler' from Radio Shack which is oil with Teflon in it.) Then get a cleaning diskette and clean the heads. (Well, 'head' in your case.) Don't do it with a q-Tip unless you have nerves of steel and know exactly what you are doing - knocking the head out of alignment is the kiss of death.

Lastly, you might be able to check the timing on the spindle - the flywheel should have 50Hz/60Hz timing marks on it. If you have a loose belt that is difficult to fix because the belts are not easy to find. Hopefully your drive is direct drive and not belt driven.

April 23rd, 2006, 07:26 AM
I think Atari drives were single sided too. Perhaps more brands, but in order to flip the disk over, the drive mustn't rely on the index hole, or you have to cut a such hole in the disk jacket too.

Terry Yager
April 23rd, 2006, 10:46 AM
In the picture, you can see the timing marks on the large pully. To check it requires no 'special' equipment, you simply spin it up under an ordinary flourescent tube, and time it for 300 rpm. There is a 'timing mark' that when spinning, the visible mark on the spindle should align with at the correct speed. If it's too fast or slow, there should be an adjusting screw.


April 23rd, 2006, 12:29 PM
And of course, the important thing to note is that it has to be flourescent. Using a standard incandescent light bulb is the path to madness ..

April 23rd, 2006, 12:43 PM

An explanation is due in regard to the choice of
flourescent versus incandescent light. :tellme:

Terry Yager
April 23rd, 2006, 01:02 PM
A flourescent tube is not a constant stream of light, it pulsates at a certain rate (60Hz?), like the timing light you use on your car's engine. Each pulse illuminates the hash-marks on the pulley in such a way as to appear as just one mark. That mark will line-up with the pointer at the correct speed. Best way to understand it is to try it. Set it up and see what happens, then you'll get it.

At least, I think that's how it works, it's been awhile.


April 23rd, 2006, 01:47 PM
Note that a neon lamp will work too, that's what most turntables (remember them?) used. Neon lamps, like flourescent lamps, don't put out a continous light, they "flash" at the line frequency (60Hz US, 50Hz in most of Europe).


April 23rd, 2006, 02:04 PM
A bit off the topic, but I believe I need to service my turntable. I found a very detailed page in Swedish how to go on, so I'll take it from there. It mentioned a stroboscope device used to check so the turntable is not skewed. I think I'll just try to lubricate it properly and hope it spins at a continuous speed afterwards.

April 23rd, 2006, 07:08 PM
Single sided drives use double density diskettes.
Double sided drives use the exact same media .. they just have the read/write heads on two sides instead of one.

Double sided and double density diskettes are made a tiny bit differently, thereofore, they are supposed to be compatible, but they are really not 100%.
For instance, my IBM 5150 FDD won't read a 180KB or 360KB formatted DD, BUT WILL read a 180kb or 360kb formatted standard double sided.

April 23rd, 2006, 07:25 PM
Double density and double sided are two different issues. You can have a double density disk that is single sided. (I have owned these - 1981, Radio Shack, $5 per disk.) Theoretically there are single density diskettes out there somewhere for older machines, but I have never seen one.

From page 1-185 of my IBM PC (5150) Technical Reference manual:

"The IBM 5-1/4" Diskette Drive uses a standard 5.25-inch (133.4-millimeter) diskette. For programming considerations, single sided, double-density, soft-sectored diskettes are used for single-sided drives. Double-sided drives use double-sided, double-density, soft-sectored diskettes."

Clearly the 5150 is designed to use double density disks, either single sided or double sided.

I can't explain what you saw on your drive, but by definition it is not an issue of double density vs. double sided.

April 23rd, 2006, 07:50 PM
I think you just resolved the issue unintentionally, maybe he was using the wrong type of disk, concenring sectoring.
I have several boxes of original disks, and the ones that came with the IBM are called double sided, they say nothing about being double density like my box of imation 5.25s. Typically the disks with a semi-shiney surface(actual disk inside of outter protector) work in my IBM, and the shiney sirface disks dont work.
I may have confised the situation with low and high density. I meant low density as standard double sided in my confusion and high density in my explanation of double density.
Oh well, so many companies were basing info off so many different disk or drive specs, it is quite hard to determine these issues.
But all my double sided labeled disks are usually 360KB(my single sides are 180KB), and all my double density disks are rated to 1.2MB.
I dont know, I guess there is something he can use information wise he can go off of, but I think he needs older disks nonetheless. I've never been successful with getting an imation to work in the ibm, or anything it's age.
I know howto format a disk to different sizes, but anything I own that says double density wont format right. Perhaps you are being too specific here, the problem may lay in the fact that some drives don't like some types of disks. For instance, for the life of me I cannot get a newer 3.5 disk to format down to 720 without some problems, but my older ibm 1.44mb, and 1mb's can format down to 720kb very easily.
Edit: to clarify, I did confuse double sided with low density, I meant to say low density, and I meant to say high density for double density..lol
Honest mistake.

April 23rd, 2006, 08:20 PM
Terminology is very important .. just to make sure we are clear:

Double density is the standard used on the 5150, 5160, and the Jr. It gives you anywhere from 160 to 360K on a disk depending on the number of sides used and the formatting.

High Density is the standard used on later machines, like the AT when equipped with a high density drive. It gives you 1.2MB (5.25") or 1.44MB. Other variations are possible with formatting tricks.

Formatting and density are not closely related. Density sets an upper limit on formatting, but that's about it. For example, you can take a brand new 1.44MB drive with high density media and lay a 720K format down on it. How? Use only 9 sectors per track. That's the same format used by a double density 720K drive, but on different media.

Could you do the reverse? Not really. You can squeeze a little more out of a diskette with formatting tricks, but if you try to squeeze too much it doesn't work. A double density disk might survive a format in a high density drive (with a high density format), but expect to lose some data.

See http://www.brutman.com/PCjr/diskette_handling.html for the gory details ...

Now back to the original problem .. If the drive was designed to be used on a n IBM compatible PC, then it's going to use soft sectored double density diskettes. Hard sectoring on a 5.25 would be quite the oddball, and it wasn't used on IBM compatibles.

I'd still look at cleaning and timing .. as Terry pointed out the timing marks are very visible, and the strobe of a flourescent lamp will show you the timing. (Good or bad ..)

April 24th, 2006, 06:12 AM
Huh... I'll check those tricks when I'll have free time... I have lot of 360KB, maybe few one-sided but they propably don't work. I have one single dentisty disk too:

one sided/single dentisty
9 X 256 bytes

The man that sold me this Simens drive gave me it.
The drive once copied correctly files from full loaded 360KB disk formated as 160KB in 360KB drive.

I've cleaned rails, there was old oil on them, I replaced it by new oil (of cource away from head and drive). I connected drive... formatted disk 100% good, and it was able to copy data. But after ~3 minutes it started to prompt: Sector not found... and started to fail formating 'Cannot write BOOT...'. I haven't doing nothing with it for ~2 days and it was standing horizontal, like few days ago i haven't doing anything wiht FDD for 1 day and when I connected it, it copied a disk. I connect it to computer vetrical, because it's too big to put it in case, and when I'll put it on desk horizontal mechanism will 'hook' the desk.

By the way, why screen on my Hercules monitor is falling? My eyes/monior or card is not OK?

April 24th, 2006, 07:41 AM
Maybe this drive wants low density disks?

Another thing to keep in mind .. don't put a monitor too close to the drive. On some machines the shielding is insufficient and the monitor will induce errors in the drive. (The PCjr is a great example of this ... if you see a picture of one used with the IBM CGA monitor, the IBM CGA monitor is always off to the side.)

April 24th, 2006, 08:24 AM
Monitor is on the left side of computer, and drive is on righ side. Single dentisty... I'am not sure but DOS 1.x and PC 5150 don't support single dentisty and this drive woldn't work on my computer if it's not compatible with IBM. There is another posibiliy that this FDD is supported by colone of IBM PC, but I think that clones of IBM 5150 don't exist... I will get something to check the speed of FDD's motor and I'll clean it better.

P.S. What's difference between 160KB/180KB drives and disks? Except sectors.

April 24th, 2006, 08:51 AM
Nothing .. Early versions of DOS (1.0?) used 8 sectors per track, which was very conservative. That got bumped up to 9 sectors per track fairly quickly.

Take a look at the BIOS interface for formatting a disk .. the flexibility for specifying oddball formats is amazing.

April 24th, 2006, 04:32 PM
Theoretically there are single density diskettes out there somewhere for older machines, but I have never seen one.
A similar discussion is currently held on Denial, and a fellow named Mark claimed that the 5.25" 48 tpi media always was the same for single and double density drives. The difference would lay in how they store data: single density drives using FM, while double density drives use something like MFM, GCR or RLL (perhaps only hard drives). I don't know how much truth it is in this reasoning, but I can't remember seeing an advertisment or product listing, much less actual floppy media being single density.

April 25th, 2006, 11:39 AM
I had nothing to do so I put FDD on desk and connected to computer, I found DOS 1.1 disk. I put it in FDD and It botted it great 'Current date...' appeared and I tried to run any program, but it failed only command, chkdsk, format and boot files worked good... I think that it can't read data from middle and end of disk.

May 23rd, 2006, 07:37 AM
Sorry for double post, but noone will answer if I'll just edit post. This FDD is strange... look at is's height:

http://img487.imageshack.us/img487/5309/cca3qd.th.jpg (http://img487.imageshack.us/my.php?image=cca3qd.jpg)

I think that it wasn't designed for IBM's PC but for clone. Someone saw someting like this FDD?