HP 9895A 8'' Floppy Drive - Problem

[Michael Fehlhammer]

I've got a 9895A dual eight inch HPIB floppy drive with a non-working second drive; my technician says that the problem definitely is a defective read head ( of head 1 in drive 1; drive 0 is working).
Therefore I am desperately searching for that spare part (read/write head). I know that these drives are rare and spare parts for them even rarer, but who knows ... maybe someone has got the part, or can name a source; I would offer some attractive other piece of vintage electronics for trade.

[cruff]

On another vein, has anyone found a source of the drive belts (60 Hz) for these drives?

[Paul Berger (Canada)]

(12-17-2019 09:59 PM)Michael Fehlhammer Wrote:  I've got a 9895A dual eight inch HPIB floppy drive with a non-working second drive; my technician says that the problem definitely is a defective read head ( of head 1 in drive 1; drive 0 is working).
Therefore I am desperately searching for that spare part (read/write head). I know that these drives are rare and spare parts for them even rarer, but who knows ... maybe someone has got the part, or can name a source; I would offer some attractive other piece of vintage electronics for trade.

You might be better off searching for a whole new drive. The drives in the 9895 use a standard 50 pin interface so they will work with most 8" drives. I am running a pair of Seagate half-high drives off a 9895 controller card for my pseudo 9895 and I have not encountered any issues.

Paul.

[Michael Fehlhammer]

Hello Paul,

thank you for these good news, I would never have thought that there could be some compatibility among these old 8 inch drives.

But which details I will have to pay attention to?

First, I need a double sided drive of course (I saw 1S drives relatively often).

And then: For example, my 9895A is configured for 230V / 50 Hz. Now I see floppy drives offered on Ebay which are labelled "60Hz 115V", what I don't understand; I thought 24V DC are supplied to the drive, transformation is done outside in the 9895A controller?

And what about the eject mechanism? I found that one on Ebay Europe:
8 inch Floppy.
Apart from the high price: It is a full-size drive, but looks very different on the front side, and I doubt that it can be modified to use the 9895A front door?
I guess you don't use the 9895A housing any more, just the electronics.
Unfortunately, as a collector I am not only interested in functionality ...

[Paul Berger (Canada)]

(12-18-2019 12:18 PM)Michael Fehlhammer Wrote:  Hello Paul,

thank you for these good news, I would never have thought that there could be some compatibility among these old 8 inch drives.

But which details I will have to pay attention to?

First, I need a double sided drive of course (I saw 1S drives relatively often).

And then: For example, my 9895A is configured for 230V / 50 Hz. Now I see floppy drives offered on Ebay which are labelled "60Hz 115V", what I don't understand; I thought 24V DC are supplied to the drive, transformation is done outside in the 9895A controller?

And what about the eject mechanism? I found that one on Ebay Europe:
8 inch Floppy.
Apart from the high price: It is a full-size drive, but looks very different on the front side, and I doubt that it can be modified to use the 9895A front door?
I guess you don't use the 9895A housing any more, just the electronics.
Unfortunately, as a collector I am not only interested in functionality ...

The 60Hz 115V would be for the motor, most if not all of the original full height 8" drives use an AC motor to turn the diskette and even if you where to provide a 220 to 115 transformer the difference in line frequency would mean the motor would run at the wrong speed which is why there are different pulleys for 50Hz and 60Hz. The half high 8" drives I have use a 24V DC motor to turn the diskette.

You are right I don't think you could make that Siemens drive look like a Shugart (I think the originals are Shugart) If you where to get a replacement Shugart, even if it was a 115V 60Hz you could swap the motor and pulley from you current drive.

Did you swap that drive electronics between the two drives when troubleshooting? Head failures are pretty rare, and since they typically have a glass surface it take a lot of use to wear down the heads. Another issue is alignment, if the drive gets a bit out of alignment, it could read diskettes created on it, but would fail to read diskettes from another drive.

I have never had a 9895 shell only the controller board, and probably an early one at that, the ROMs on the board are PROMs with hand written numbers on them.

Paul.

[Michael Fehlhammer]

(12-18-2019 04:08 PM)Paul Berger (Canada) Wrote:  You are right I don't think you could make that Siemens drive look like a Shugart (I think the originals are Shugart) If you where to get a replacement Shugart, even if it was a 115V 60Hz you could swap the motor and pulley from you current drive.

Ok, I will look out for a Shugart drive!

(12-18-2019 04:08 PM)Paul Berger (Canada) Wrote:  Did you swap that drive electronics between the two drives when troubleshooting? Head failures are pretty rare, and since they typically have a glass surface it take a lot of use to wear down the heads. Another issue is alignment, if the drive gets a bit out of alignment, it could read diskettes created on it, but would fail to read diskettes from another drive.

I think my technician swapped the drive electronic boards in order to isolate the source of error, but I have to check that.
I understand that the surface of a read head can't easily be damaged. What about the coils? Could problems with the power supply (overvoltage) damage these?

Anyway, thanks for the suggestions! We won't give up soon, such a precious piece of computer history deserves big repair effort.
By the way, I just have heard that only ten years ago a 9895A, along with an HP 9845 computer, have been trashed at a German university. Well, that probably has been the fate of many old electronics devices, but still - it hurts.

[Paul Berger (Canada)]

You should look at the drives in you 9895, looking at the manual it appears they may be CDC drives and not Shugart.

[Michael Fehlhammer]

Paul, you are perfectly right. The drive is a cdc drive, BR8A8-A. there are service manuals available that come close, but do not match exactly.
We swapped the drive heads and proved them to be ok. As Paul has assumed the problem lies on the floppy controller board. After some fiddling around the first drive (which worked fine initially) now also fails. It still reads correctly, but now it destroys data on the disk (probably the directory) when writing anything (proved by a second 9895A in working condition). It also cannot format a disk.
So now we have drive 0 which can read but not write, and drive 1 which can't read.
(writing can't be tested, since verify fails and a write command will never finish).

The floppy controller boards are revision 3, which unfortunately is not described in the available manuals (CDC 9404, 9406).
Moreover, the two boards differ slightly, and obviously there have been repair attempts for board 1. For example, sealed potentiometers have been adjusted subsequently, and ICs have been replaced.
We probably will have to find out which components control read and write access and replace one after another. Maybe we will need some help from the community to identify special ICs. There seems to be no easy way, but hints and tips are welcome.
By the way, we experimented with the radial alignment of the print heads. At least we were able to improve read access in that sense that drive 0 finally managed to read disks that were recorded by another drive.

[Hans Brueggemann]

michael, before you jump into fault isolation on individual components, i strongly suggest to replace all (and i mean all, no matter how unsuspicious they look) electrolytic and tantalum capacitors with fresh (as in fresh eggs, not NOS) ones from your preferred catalog distri, and have a close look at all power supply rails before commencing any further repair attempts.

[Michael Fehlhammer]

Hello Hans,
thanks for your suggestion, we will follow that path.