The FD-50 Series

Last revision of this page: April 18, 2025

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FD55 technical specifications — TEAC FD-50 advertising [1]

The third paragraph on the right is somewhat contradictory, because it refers to single-density, but at the same time uses the term MFM. This is double-density. Perhaps it should also be written as single-sided. That would be correct. Now then.

A little research on the internet has shown that the TEAC FD-50 was used in the TRS-80 model III, the Video Genie and the NEC PC-8001 with the external NEC PC-8031BE/8032E double floppy disk station and the DEC RX180 external drive. According to Chuck Guzis (Sydex: 22DISK), the FD-50 is or was not as reliable as the later FD-55 drives; Chuck uses the term terible! [4]

In addition to the FD-50 and FD-55, there is also the FD-54. I use the FD-54B-02-U in my floppy disk station and have had no negative experiences with it so far.

Here are some FD-50 related links to the Vintage Computer Forum (VCF):

Technical Specifications

Attention: According to the (sparse) information available to me, the C and D versions are 100 tpi (not 96 dpi) drives!

FD-50A: SS, 48 tpi, FM, MFM
FD-50B: DS, 48 tpi, FM, MFM
FD-50C: SS, 100 tpi, FM, MFM
FD-50D: DS, 100 tpi, FM, MFM
FD-50E: SS, 96 tpi, FM, MFM
FD-50F: DS, 96 tpi, FM, MFM

Jumper Settings

MX Jumper

From: Ben Zotto, San Francisco, USA (04/18/2025)

Hi Thomas,
I used the schematics on your extremely helpful site to repair a broken TEAC FD-50 5.25" floppy mechanism recently. Interestingly enough, it was one of two inside a DEC RX180 unit, which you also provided helpful information about (although your drive units were Shugart, I think). Thank you so much!
Anyway, I wanted to offer a bit of useful context that surprised me (and prevented my drives from working until I figured it out) that you might be interested in including on your page, since it's the only page on the internet with information about the FD-50 mechanism that I know of:
The MX jumper must be set (=shorted, closed, on) when more than one drive is used on an interface cable. This seems to be the opposite of most other Shugart-like 5.25" mechanisms! On most mechanisms, the MX jumper is used to ignore drive select for single-drive-only systems. I have no idea why the TEAC drive behaves this way-- it doesn't seem like a very useful setting, but I could find only schematics through your site, and I've never found a manual. But my real-world experience confirmed that unless MX is set, the output signal drivers are always on, and cause bus conflicts if more than one drive is on the cable.
Anyway, hope that's an interesting tidbit. Thanks again for hosting such helpful info on your site!
...
I should also have clarified that the mech model in the DEC unit is FD-50A-03-U -- does not appear in the table in the schematic but it's a SS 48tpi and had the following straps on the PCB: 1, 8, 10, 13, 15, 21 (and possibly 29, because that seems common to all of the PCBs). Definitely supports FM but I didn't try double density use so not sure.

Images

Information

TEAC FD-50 schematics only (I do not have the complete manual)

References

(↑) InfoWorld, Sep 1, 1980, page 26
(↑) Michael Tooley, Servicing Personal Computers, 2nd Edition, page 246
(↑) Ben Zotto, San Francisco, USA
(↑) Chuck Guzis about the Teac FD-50