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What interface does this Teac 5.25" drive have?

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Malvineous

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Hi all,

I have had very little exposure to Apple products so I'm hoping some experts might be able to help. I recently purchased a "new in box" 5.25" floppy drive sight unseen, and it turned out to be a Teac FD-55A (single sided, double-density, 40 tracks.) To my surprise, it turned out to be an external drive in its own enclosure (something I have never seen in person before) and a 20-pin IDC ribbon cable was hanging out the back.

I've done a little research and it seems that this could be compatible with the early Apple "direct drive" floppy drives. Opening the case revealed a very interesting addition to the drive - a small board that adapts the 20-pin cable partly to the drive's PC-style Shugart interface, and partly connects it directly to (I assume) the head stepper control circuits. The 20 pin ribbon cable connects to the white header that is blocking the PC-style power connector.

Does this look like it could be an Apple interface? Or were there other 20-pin data+power interfaces that it could also be?

I am considering removing the interface to convert the drive back into a standard PC drive (although of limited use being only single-sided, so only early DOS 160/180kB floppies will be usable) but before I do, I thought I had better check whether these types of drives are rare in this configuration and whether it would be better to keep it as-is, in case it turns out to be more useful/valuable to someone else in its factory state.

The forum seems to make the attached images a bit small so some of the full-resolution Vogonswiki pics might be clearer.

Any opinions/info? Thanks!
 

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Interesting. I wonder if that daughterboard is general-purpose enough to be able to adapt other PC drives as well. Certainly the places it hooks up to the Shugart interface would be standard. Just the stepper connections would be tricky.
 
That is odd, most Apple II clone floppy drives have their own custom logic board. But that does look like a Disk II interface. To be sure perhaps you could use a volt meter to find which pins connect to the power and compare that to the Disk II pinouts.

According to this, the 55A is a single sided drive: http://bitsavers.trailing-edge.com/pdf/teac/FD55_Spec.pdf

Personally, I would leave it as is. That should make a nice reliable Apple II drive. And a single sided half height drive isn't very useful in an IBM PC environment. Also keep in mind it is not possible to completely remove solder from the gold fingers.
 
I think that's the model I had years ago, but it must have had an adapter for the //c. Pure joy when we got it and I could stop playing disk toaster.
 
Thanks for the info! I did the continuity test and this confirms it is a Disk II interface. The +12V, GND and +5V lines all match the listed pinouts for Disk II. The four Disk II phase signals are the lines that are soldered directly onto that IC - they don't seem to go via the little interface, they seem to go straight from the external connector to the IC.

I guess this means it's a possibility to convert other PC drives to Disk II, providing you can find where the stepper phase signals come from. Perhaps there are other modifications though, like cut traces so the Shugart interface isn't generating phase signals on the same lines.
 
Isn't the encoding different, though? A Teac FD-55A for a PC would be MFM whereas for an Disk II is GCR? I wouldn't think you could take a PC drive and just add an interface in front of it? Either the analog card on the drive would be different or the controller card in the slot to get GCR? I could see tacking on an interface to get a PC drive to R/W from an Apple II but the media wouldn't be the same ... Larry G

PS - or is the encoding all determined by the controller card?
 
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Hello,
The added board seems to be quite simple. Just few chips.
Is there a possibility to get detailed pitures of this converter board (top/bottom) and from the connections to the mainboard ?
Thanks in advance.
 
It wouldn't seem to be very difficult to work out a converter board. If you've got Jim Sather's book handy, it should be a slam-dunk.

Most of the Apple-specific stuff on a floppy drive (not the controller) was done as a cost reduction approach. An OEM order for bare drives undoubtedly save Apple a bunch of money back in the day.
 
Back in 1982 I just purchased my AII. I found some Shugart SA-400 drives at California Digital that were less than half the price of new Disk II drives. The interface was the standard 34 pin edge connector. I thought about modifying this to interface it to the Disk II controller but since I worked for a Apple dealer I just ordered Disk II analog boards and enclosures. Still saved over $100 per drive. These had an added head load relay in them Disk II drives didn't have. Gave my AII a distinctive sound! Chuck is right it wouldn't be very hard to make an adapter board for 34 pin to Disk II.
 
The OP's picture of it makes me cringe, though. I sure wouldn't solder 4 consecutive wires close to the body of the stepper IC like that. It has to weaken it somewhat. That's a lot of heat in the area.

Larry G
 
Okay, I've understood it's simple.
My question is : how do I do that ? Any schema ?
I do have an A.E. 5.25 drive which connects to the A.E. Transporter card. I don't know if it's the same type of interface.
 
I found this old thread when searching for a way to read my old Apple II disks.
So far, Treckr Apple II reader Project looks best as a base, but I do not have Apple disk drives any more. So I thought, maybe an original TEAD FD55A might do it with little modifications of the stepper interface lines to step/dir.
But how about the other signals? It would be a great help if I got a schematic of the little conversion board seen here in this thread.
Anybody able and willing to share information about it?

Thanks
Uli
 
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ulihuber said:
I found this old thread when searching for a way to read my old Apple II disks.
So far, Treckr Apple II reader Project looks best as a base, but I do not have Apple disk drives any more. So I thought, maybe an original TEAD FD55A might do it with little modifications of the stepper interface lines to step/dir.
But how about the other signals? It would be a great help if I got a schematic of the little conversion board seen here in this thread.
Anybody able and willing to share information about it?

Thanks
Uli
Click to expand...
I found this old thread https://forum.vcfed.org/index.php?threads/another-disk-drive-diagnosis.14693/ - about a similar drive. It sounds like modifications to the main board are also required. Unfortunately the high-res photo links no longer work - maybe @tezza would be able to re-upload them?
 
Would like to see a reproduction of this mod. I have a single sided BASF drive that would be perfect for a second Disk ][.
 
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