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5.25 MFM Floppy Drive
- Thread starter Maraud
- Start date
Chuck(G)
25k Member
Just curious, why a single-sided one specifically? They exist, but are pretty thin on the ground in half-height form factor. On the other hand, a double-sided drive is easier to find and can handle single-sided floppies just as well.
MikeS
Veteran Member
Now I'm also curious: I'd have thought that by the time half-height drives arrived they'd all have been DS; got a make/model example?
vwestlife
Veteran Member
I haven't seen any for IBM compatibles, but plenty of other brands used half-height, single-sided floppy drives: Apple, Commodore, Atari, Radio Shack, etc...
Chuck(G)
25k Member
For a HH 5.25" SS drive, consider the Teac FD54A drive (as used in the Sanyo MBC-555). There was also a FD55A (and 96 tpi FD55E) single sided drives.
MikeS
Veteran Member
Yeah, I was only thinking standard PC-types, but not thinking very clearly since I have the MBC-555 that Chuck mentioned as an example... Duh!
carlsson
Veteran Member
I also have a single sided, half height floppy drive at home. It once came from a BBC Micro but is IBM PC compatible as far as you can get with a drive that only can read one side of the disk. It may be so the drives were made long after the industry moved to half height drives, but that PC manufacturers went for double sided drives and other brands using compatible drives for cost (?) reasons stuck to single sided drives.
Chuck(G)
25k Member
Yup, it was cost--heads were a significant part of the cost of a drive. Often, the PCB for single-sided drives was the same as that for double-sided.
The exact unit I'm trying to replace is a TEC FB-501. Thanks Chuck for the pointers for the other model numbers, I'll see if I can find any of those. I'm trying to replace the internal mech for a MSD-SD1 for a Commodore. Neat little contraption that somehow was able to use a MFM drive to read/write to GCR encoded disks. The original mech failed. I tried a DSDD unit but it gets read errors. I was hoping it ignore the "2nd side" but there's obviously more to it. The good news is that at least the drive seeks and such so I know that part works! 
MikeS
Veteran Member
There isn't necessarily much "more to it;" I've replaced a TEC (I think it was an FB-501) with a "normal" DS/DD Panasonic drive with no problems except that as I recall the TEC was shorter, which created a mounting challenge in that particular chassis.
Are you sure that the replacement drive is 100% and the diskettes you're trying to read don't in fact really DO have read errors? Have you tried formatting and writing to a new disk in the replacement drive to see if it can read those?
Are you sure that the replacement drive is 100% and the diskettes you're trying to read don't in fact really DO have read errors? Have you tried formatting and writing to a new disk in the replacement drive to see if it can read those?
carlsson
Veteran Member
Anyway, isn't the data encoding a feature of the disk controller, whether it is a circuit board mounted onto the drive mech or part of an expansion or motherboard in the other end of the cable? With that I mean the mech itself might be usable with either kind of encoding depending on the circuitry it is used with.
Chuck(G)
25k Member
Yes, that's true--most floppy drive (with the exception of SCSI, IDE, USB and other high-level interfaces) read-write channels are basically brain-dead. Put anything you want on the write data pin while asserting write gate and you'll read a pulse back every time the magnetization changes polarity (within the bandwidth of the read/write channel).
MikeS
Veteran Member
Yeah, as a rule the drive doesn't care about the encoding method, FM, M2FM, MFM, GCR, whatever, and the second side of a two-sided drive is simply ignored by a single-side controller. The TPI and density have to match of course and the logic of the interface signals might be a little different, but that usually just involves changing some jumpers.
Getting read errors as opposed to 'drive not ready' etc. does suggest that the drive may well be compatible and that the errors are in fact legitimate read errors.
BillT356
Experienced Member
I have 2 TEAC drives (HH, 360K, 40 track, MFM) Model # FD-55BV-06-U, that I can part with. Where are you located? My zip is 08005.
Thanks BillT - I'm in FL 32701. Just PM me (or email me at spkenny at gmail dot com) with what you'd like funding wise.
And to answer the previous questions, I have tried formatting a new disk and same deal, it does send the heads to track 18 where the allocation map is and then to track 1 and dies.