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The Memotech MTX Series

  Memotech Floppy Disk Drives

 Photographs and Technical Data

 FDX System  5.25" and 3.5" SDX Systems


The features of the various Memotech floppy disk drive expansion options are discussed on the Memotech Disk Options page. This page describes the details of the various types of floppy disk drives originally used in the FDX & SDX systems. (Since identical replacement drives are pretty much impossible to source, a number of alternatives for faulty drives in Memotech systems are discussed in this Technical Note.)

The first Memotech floppy disk system was the FDX, the case had sufficient space to install up to 2x5.25" floppy drives internally. The FDXC1 disk controller supported up to 4 floppy disk drives, which could be any combination of 5.25" and 8" drives mounted internally (5.25" only) and externally. Even at the time that the MTX was released, 8" floppy drives were becoming a rarity and I don't think many FDX units were shipped with 8" drives. In any event, as far as I am aware, there are no 8" Memotech disk systems around today, or at least, since I have no details about them, this page is restricted to coverage of the 5.25" FDX/SDX drives and the later 3.5" SDX drive.

FDX 5.25" Disk Drives

FDX Floppy Disks OEM Drive Facia

The FDX was supplied with at least two types of 5.25" disk drives, the Qume, QumeTrak 142, and the Epson, SD-521.


The easiest way to tell them apart is the facia, although an IBM badged drive is shown here, the FDX Qume drive is the same (minus the logo) and uses a disk eject lever, whereas the Epson drive uses a push button disk release mechanism.

QumeTrak 142

Epson SD-521

QumeTrak 142

The first floppy drives used in the FDX were manufactured by Qume, and were QumeTrak 142 5.25" drives with an unformatted capacity of 500kb. The same drive, with an IBM logo, was used on the IBM-5155 "portable" computer and unfortunately, does not have a very good reputation for reliability, sadly, this is borne out by my own experience with at least 2 of the Qume drives in my FDXs having failed .

Specifications Single Density Double Density (FDX)
Capacity (per disk)* Unformatted 250k Unformatted 500k
  Formatted 163k Formatted 327k
Recording Density 2938 BPI 5876 BPI
Track Density 48 TPI 48 TPI
Cylinders 40 40
Tracks 80 80
Recording Method FM MFM
Rotational Speed 300 RPM 300 RPM
Transfer Rate 125k bits/sec 250k bits/sec
Average Latency 100 ms 100 ms
Average Access Time 160 ms 160 ms
Track-to-track Seek Time 12 ms (6 ms optional) 12 ms (6 ms optional)
Spindle Drive Mechanism Belt Belt

* The capacities shown are from the drive manufacturers data sheets, when used with Memotech systems, the disk capacity was dictated by the format used, in the case of a FDX Type 03, this was 256 bytes per sector, 16 sectors per track and 80 tracks, giving a formatted capacity of 320k.


Photos will appear here



Maintenance Issues (from

Common problems this many years from manufacture include:

  • Dirty heads. Gently wipe over both heads with a cotton bud dipped in isopropanol.

  • Sticky head mechanism. The service manual states that a 50g weight attached to the head mechanism should be enough to pull the head to either stop, with the drive on end as required. In practice the head mechanism should move easily. It is prone to become sticky especially at the ends of travel, in which case the drive may fail a BIOS seek test (reporting floppy drive failure).
    This can be easily resolved by first cleaning the three rails thoroughly (again with cotton bud dipped in isopropanol) and then applying a little grease again with a cotton bud, and moving the heads a few times to get an even and thin coating on the rails. Finally wipe away any excess.

  • Stiff lock handle, with poor spring tension when released. Again a lubrication issue. Close the door lock, and remove the screw from the door pin actuator at the front of the drive (a single cross-head screw) and slide it back a little. Next stand the drive on end as required and apply one drop of 3-in-one oil to the door lock shaft ends, such that it runs down in to the plastic bearing. Reposition and secure the door pin actuator and open the drive lock, and then apply a little grease to the spring cam half way along the shaft on the faces that will turn against the spring. Finally operate the lock a few times to work the oil and grease in fully.

  • Dirty optos. There are three opto sensors - read-only tab, disk position, and head track 0 position. All three can be cleaned with a cotton bud dipped in isopropanol that has first been compressed such that it will fit in the openings.

The Qume Maintenance Manual for this drive is available on my Manuals Page.

Both of my FDXs were fitted with QumeTrak drives, the ones in my original MTX were fine when last used in the late 1980s and also appeared to work when last tried in 2009, but sadly, both failed in short order after being fired up again in 2013. The drives in the FDX that I bought off ebay in 2009 both appeared to be faulty when I received the FDX. I am currently looking for replacement drives to resurrect my FDXs.


Epson SD-521

Physical Specifications

Capacity* Unformatted 500k
  Formatted 360k bytes (IBM)
Recording Density 5876 BPI
Track Density 48 TPI
Cylinders 40
Tracks 80
Recording Method MFM
Rotational Speed 300RPM
Transfer Rate 250k bits/sec
Average Latency  
Average Access Time  
Track-to-track Seek Time 6 ms
Spindle Drive Mechanism Direct



Photos will appear here


These drives were also popular with other computer manufacturers, but surprisingly, I have been unable to locate any additional information about them, if you are aware of any documentation - User Guide, Service Manual, etc. please let me know.


SDX 5.25" Disk Drives

SDX Floppy Disks - 5.25" OEM Drive Facia

The 5.25" version of the SDX had 1 or 2 5.25" drives, each in its own metal case.


Based on the photos in the Memotech adverts, I think the 5.25" SDX probably used an Epson drive like the later FDXs.


The top photo is of the SD-521 facia, the photo in the centre is a poor quality photo cut from one of the SDX adverts and the drawing at the bottom is also taken from the same advert.

Epson SD-521

Advert Photo
Advert Sketch
The SDX also supported 80 Track/1 MB drives, based on the photo of Peter's 5.25" SDX, this included the Teac FD-55GFR

Teac FD55-GFR

This controller also supported 3.5" drives, but I have not actually seen a 3.5" drive on one of these controllers.    


MTX512S2 Type 3.5" Disk Drives


SDX Floppy Disks - 3.5" OEM  
The later version of the SDX, introduced with the MTX512S2 had an integrated 3.5" FDD. They are much more difficult to identify from photos, but one example of the drives used is in this 3.5" SDX.

The FD-1036 was a DS/DD drive with an unformatted capacity of 1MB.

NEC FD-1036


Physical Specifications

Capacity* Unformatted 1Mb
  Formatted 720k bytes (IBM)
Recording Density 8317 BPI
Track Density 135 TPI
Cylinders 80
Tracks 160
Recording Method MFM
Rotational Speed 300RPM
Transfer Rate 250k bits/sec
Average Latency  
Average Access Time  
Track-to-track Seek Time 6 ms
Spindle Drive Mechanism Direct

Replacement Drives

After the power supplies, the floppy drives are probably the most unreliable component in the Memotech disk systems. When these drives fail, it is most unlikely that you will be able to source identical replacements - this is particularly true for the 5.25" drives. A number of alternatives that have been found to work with the FDX  - these are now discussed in a separate Technical Note.




Reference : Some very useful information on floppy disk drives can be found at :


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