TEAC FD-55GFR 5.25" Floppy Configuration for NGEN/AWS 300 RPM vs Standard PC 360 RPM - "A Tale of Two TEACs"

Jump directly to JUMPERS (pun intended)

While most of these drives operated in the world as 1.2Mb.  But with the Convergent Technologies AWS & NGEN machines, it's a different story.  Those systems use "Quad Density", which is basically 80 tracks (or 77 in this case, where the last 3 are just ignored), and the drive RPM runs slower, at 300 rpm instead of 360 rpm.  

But what jumper(s) change the drive speed from the default 360 rpm down to 300 rpm?

All manuals we find for the TEAC FD-55G-series show radically different jumper positions and names, so they are unfortunately, not helpful.  But we still want to know, so through real-life comparison and process of elimination, we're going to find out!

First, the NGEN/AWS configurations, running 300 rpm:

Now compare to the "Normal" PC Configurations running 360 rpm

There's a LOT fewer jumpers on the Standard PC drive running 360 rpm

Here's the differences highlighted:

Note some of the more confusing jumper labeling:

Note to Self:  Edit below image, some jumpers are labeled wrong

Notice that some of these jumpers used for the NGEN/AWS aren't even INSTALLED on this drive!

But what we REALLY want to know, is which of these jumpers changes the drive speed from 300rpm to 360rpm?  Well, through trial and error, we figured it out.

First, we had to "install" jumpers on the missing one, to start out at the same place as the AWS settings...

Then remove them one-by-one, re-testing the drive each time, until the RPM dropped from 360 to 300.

So which jumper is it?

Jumper "I"

NOT to be confused with HL:

Also, if you rotate it 90 degrees, as some markers are, this could look like 

an H instead of an I.  How confusing....

So what do all of those other jumpers do?  Well, we'd have to go through a LOT more trial and error, and we're not really sure what we'd be testing for with the removal of each jumper.  SO, before we do that, does anyone know how to tell what all these marked jumpers do, maybe from a manual that we haven't found online yet?

S6

FG

MX

DC0

HL

IU

U0

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