Figuring out the test points won't be a problem since they use a '3470,
which is also used in the Siemens drives. I doubt there's much difference
in the circuitry. Oddly enough, I have two of the Tandon drives and no
manuals, and none of the Shugart "half-height" drives and both of their
What really troubles me is that after rejumpering the drives to match the
data kindly provided by Don Maslin, the two drives behave somewhat
differently, though they do now read one another's writing. What's more,
the jumpers on the drives, though the drives are the same, don't match Don's
data completely. There are jumpers not on the drives which are on the list,
and jumpers not on the list which are on the drives. Examined in detail,
the drives appear the same, though the boards are of different revision.
Perhaps the code in the on-board processor is different.
From: Tony Duell <ard(a)p850ug1.demon.co.uk>
To: Discussion re-collecting of classic computers
Date: Saturday, July 31, 1999 12:38 PM
Subject: Re: floppy disk drive manuals
> I have a couple of Tandon 8" slimline drives (They're in the basement and
> I'm not so no model number.) They clearly can't read one another's
> consistently, so I'm interested in alignment
data as well as the jumper
> definitions. Would you have a manual which contains that information? I
> need to know what the jumpers are and do, and what the factory default
> settings are. I also need to know where the dif-amp outputs to be used
located, (pin numbers) as well as the index sensor pin and
other signals used in adjusting these drives for radial head alignment,
index alignment, track zero calibration, etc. If you have it and could
email me that data, it would help greatly.
I know _I_ don't have that info, but that doesn't mean we can't make some
sensible attempts to align them. I have the SA800 and SA850 manuals to
hand, and I may have a couple of obscure 8" drive manuals somewhere.
Nothing Tandon, though.
You can always use the interface connector as a source of the Index
signal. And of course to move the head around.
So the only thing you're missing is the output of the read amplifier. If
the read circuitry is in a custom chip you might be out of luck. But a
lot of drives use 592 or 733 amplifier chips at the start of the read
chain, whereupon you look at the outpus (7 and 8) of that chip with a
'scope. If there's an MC3470 as the only chip in the read chain, look for
testpoints in the filter network connected to pins 14,15,16,17.
If it's a custom chip, look for 2 testpoints and ground (often, but not
always TP1-TP3 in some order) connected to a symmetrical filter network
hung off the chip, Look for read-type waveforms when reading a disk that
was written in that drive.