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WTB: more reliable S-100 8" floppy drive(s)

J

JNZ

Experienced Member
Joined
Sep 4, 2015
Messages
167
Location
Utah
I have two Siemens FDD 100-8 floppy drives on my S-100 system, along with a spare, and I'm using a Jade Double D disk controller board. I've done what repairs I can (designed and 3D printed some components for the drive latch mechanism, replaced the felt head load pad, checked the PLL with my oscilloscope as I recall) but they're still quite unreliable. I can get CP/M to boot from a known-good disk about 50% of the time, but loading programs seems to always fail.

If I had the necessary documentation and disk/tools I could try calibrating these drives, but I'm thinking it'd be better to get a more reliable drop-in replacement drive.

Does anyone have something that'll fit the bill? I hear Shugart SA-800/801 single-side full height drives are very reliable, with some others being strong contenders as well. I'd also be interested in hearing about the calibration procedure and what I'd need to get to do it.
 
I've never owned one, but I've heard those Siemens drives are well built. Sounds like you just need an alignment
 
maxtherabbit said:
I've never owned one, but I've heard those Siemens drives are well built. Sounds like you just need an alignment
Click to expand...

What's involved in the alignment? I heard you need an alignment disk, and presumably you check observed magnetic flux via a test point, and then adjust the signals feeding the stepper motor. I'm guessing you have to check the frequency and cleanliness of the PLL(s) too, over a variety of conditions and seeking patterns.

Do you need a functioning system to do an alignment?
 
The easy way, without an analog alignment disk, is to take a known-accurate floppy and set the drive up on (preferably) a PC and use something like Imagedisk to read track IDs continuously. (the alignment function). Loosen (slightly) the screws securing the head positioner motor and gently twist it slightly one way or the other, until IDs read consistently (i.e. you see all sectors). Periodically, rezero the head position and check several tracks. Snug the screws up and you're good. This assumes that someone hasn't fouled up the track 0 sensor (do clean it before you start, as dirt can affect its functioning.
 
Chuck(G) said:
The easy way, without an analog alignment disk, is to take a known-accurate floppy and set the drive up on (preferably) a PC and use something like Imagedisk to read track IDs continuously. (the alignment function). Loosen (slightly) the screws securing the head positioner motor and gently twist it slightly one way or the other, until IDs read consistently (i.e. you see all sectors). Periodically, rezero the head position and check several tracks. Snug the screws up and you're good. This assumes that someone hasn't fouled up the track 0 sensor (do clean it before you start, as dirt can affect its functioning.
Click to expand...

What do you recommend for using an 8" drive on a PC? I see there's something called the KyroFlux which looks available, for ~$150 + tax, VAT, and shipping from the UK.

I don't mind tracing the board and looking at signals with an oscilloscope or logic analyzer. I wonder if MicroSolutions on this board can share some knowledge on this. I could PM him or make a thread in the S-100 forum.
 
krebizfan said:
A cheaper alternative is http://dbit.com/fdadap.html
Click to expand...

I also posted some years ago, the correspondence between 34 conductor disk connections and 50 pin 8" ones. It's also in the 22Disk documentation and a host of other places, including Q14 here. I'm sure that there are many other places as well.

I also have a couple of small PCBs that have a 34-pin and a 50-pin header on them; no active components, just interconnections between the two. Made by Micro Solutions.
 
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JNZ said:
I don't mind tracing the board and looking at signals with an oscilloscope or logic analyzer. I wonder if MicroSolutions on this board can share some knowledge on this. I could PM him or make a thread in the S-100 forum.
Click to expand...

I think you are referring to Michael Louie (user name "MicrocomputerSolutions") who had a considerable amount of experience with 8" floppy drive repair. Michael passed away last year.

I also highly recommend use of the DBIT FDADAP adapter to connect an 8" drive to a PC floppy controller. The $40 it costs is well worth it in terms of the time you save having to reliably jumper a PC floppy controller cable to mate with an 8" floppy controller cable, and its automatic management of the "TG43" signal is an added bonus.
 
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JNZ said:
What do you recommend for using an 8" drive on a PC? I see there's something called the KyroFlux which looks available, for ~$150 + tax, VAT, and shipping from the UK.
Click to expand...

A Kryoflux is one solution for recovering data from floppy disks using a modern PC, but what you are trying to do is not to recover the data but purely to use Imagedisk as a poor mans way of checking the alignment of your 'unreliable' drive.

You should check the system requirements for the PC and floppy controller for ImageDisk before you go down this path.
I'm assuming you've cleaned the heads ;-)

Any possibility of borrowing a known good drive to confirm yours have a problem?
 
hmb said:
I think you are referring to Michael Louie (user name "MicrocomputerSolutions") who had a considerable amount of experience with 8" floppy drive repair. Michael passed away last year.

I also highly recommend use of the DBIT FDADAP adapter to connect an 8" drive to a PC floppy controller. The $40 it costs is well worth it in terms of the time you save having to reliably jumper a PC floppy controller cable to mate with an 8" floppy controller cable, and its automatic management of the "TG43" signal is an added bonus.
Click to expand...

Ahh, I'm really sorry to hear that. He had offered some good advice back when I got the system, and mentioned common pitfalls of drives. He had offered drive alignment service, but I wanted to learn how to do it myself.
 
exidyboy said:
A Kryoflux is one solution for recovering data from floppy disks using a modern PC, but what you are trying to do is not to recover the data but purely to use Imagedisk as a poor mans way of checking the alignment of your 'unreliable' drive.

You should check the system requirements for the PC and floppy controller for ImageDisk before you go down this path.
I'm assuming you've cleaned the heads ;-)

Any possibility of borrowing a known good drive to confirm yours have a problem?
Click to expand...

The disks themselves are known-good, so I suspect it must be the drives or the controller. Borrowing a drive would definitely narrow it down.
 
JNZ said:
I have two Siemens FDD 100-8 floppy drives on my S-100 system, along with a spare, and I'm using a Jade Double D disk controller board. I've done what repairs I can (designed and 3D printed some components for the drive latch mechanism, replaced the felt head load pad, checked the PLL with my oscilloscope as I recall) but they're still quite unreliable. I can get CP/M to boot from a known-good disk about 50% of the time, but loading programs seems to always fail.

If I had the necessary documentation and disk/tools I could try calibrating these drives, but I'm thinking it'd be better to get a more reliable drop-in replacement drive.

Does anyone have something that'll fit the bill? I hear Shugart SA-800/801 single-side full height drives are very reliable, with some others being strong contenders as well. I'd also be interested in hearing about the calibration procedure and what I'd need to get to do it.
Click to expand...
I’m interested in the 3D printed components you mention here. I also have 2 x siemens FFD 100-8 drives, the eject mechanism seems to be broken or intentionally disabled.
There seems to be a plastic latch with 2 metal pins, latch is connected to the top frame that, when raised, should fire the disk out the front.?
 
fdiskitup said:
I’m interested in the 3D printed components you mention here. I also have 2 x siemens FFD 100-8 drives, the eject mechanism seems to be broken or intentionally disabled.
There seems to be a plastic latch with 2 metal pins, latch is connected to the top frame that, when raised, should fire the disk out the front.?
Click to expand...
Here's a zip of the two STL files, the door latch mechanism and the head loader. I didn't do anything with the eject mechanism, but I took some pictures
 

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Thankyou for the pictures - very helpful and exactly the zone where I have an issue.
- its this metal bar part that is confusing me.... there is a second bar hidden below that pulls up and releases the disk latch (?) when the top frame goes up ?
 
my latch is stuck forward of the metal seat, on both drives. I think I will have to remove the front of the drives to raise the carriage up and push the latch back. It may never have been installed correctly…or was set up deliberately that way?IMG_2808.jpeg

Good news is that the drives spin, the head loads, and I can make it seek from a 486 using a 50 to 34 pin adaptor. No luck formating a disk yet, imd and Nformat move the head, but it seems to hit the stops and forget where it is. Possibly termination on the drives or jumper settings on the adaptor.
 
I have some 8" floppy drives kicking around, lmk if you are still interested in going that direction and I'll dig them up and let you know what brand/model they are.

All are as is, though, I have never lit any of them up.
 
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