12 Feb
2020
12 Feb
'20
4:49 a.m.
I've got a couple of Teac FD-54B's that appear to have problems with their
index sensors. Does anyone have any docs for these? The internet seems to
barely know they exist vs the FD-55, which has info everywhere. I'm thrown
off a bit by the 3 wire phototransistor (vs the common 2 wire ones) they
they use, and I haven't quite disassembled it enough to figure out a part #
for that.
Also, if anyone has a pair of spare black FD-55B, that'd be useful too.
Patrick Finnegan
15 Feb
15 Feb
10:38 a.m.
On 2/12/20 4:49 AM, Patrick Finnegan via cctalk wrote:
I've got a couple of Teac FD-54B's that appear
to have problems with their
index sensors. Does anyone have any docs for these? The internet seems to
barely know they exist vs the FD-55, which has info everywhere. I'm thrown
off a bit by the 3 wire phototransistor (vs the common 2 wire ones) they
they use, and I haven't quite disassembled it enough to figure out a part #
for that.
Herb Johnson (retrotechnology) has a service manual; also look in the
Tandy 1000 service manual--ISTR that there's an FD54 techref buried
somewhere in the middle of that thing.
-Chuck
10:47 a.m.
On Sat, Feb 15, 2020, 13:38 Chuck Guzis via cctalk <cctalk at classiccmp.org wrote:
On 2/12/20 4:49 AM, Patrick Finnegan via cctalk
wrote:
After more diagnosis, it looks like they're TTL level output photo
detectors. They have the same looking part for the write protect notch,
though that one isn't stuck high.
I'm not sure why the index sensors on both are broken, but not the write
protect notch sensors. Hopefully once the replacements arrive, replacing
that will fix the drives. The drives look pristine on the inside.
Pat
I've got a couple of Teac FD-54B's that
appear to have problems with
their
index sensors. Does anyone have any docs for
these? The internet seems to
barely know they exist vs the FD-55, which has info everywhere. I'm
thrown
off a bit by the 3 wire phototransistor (vs the
common 2 wire ones) they
they use, and I haven't quite disassembled it enough to figure out a
part #
for that.
Herb Johnson (retrotechnology) has a service manual; also look in the
Tandy 1000 service manual--ISTR that there's an FD54 techref buried
somewhere in the middle of that thing.
11:38 a.m.
On 2/15/20 10:47 AM, Patrick Finnegan wrote:
I'm not sure why the index sensors on both are
broken, but not the write
protect notch sensors. Hopefully once the replacements arrive, replacing
that will fix the drives.? The drives look pristine on the inside.
The biggest (and most misleading) issue with optical index sensors tends
to be dirt. The phototransistor or LED gets obscured by crud and ceases
to operate, even though electrically, it's fine.
The same phenomenon accounts for many so-called "alignment" issues with
floppy drives--the track zero sensor gets crud and the position at which
the sensor is interrupted changes. It's a mistake to attempt to
re-align a drive before cleaning the sensor. In reality, most floppy
drives do not exhibit drifting alignment.
--Chuck
1:11 p.m.
On Sat, Feb 15, 2020, 14:38 Chuck Guzis <cclist at sydex.com> wrote:
On 2/15/20 10:47 AM, Patrick Finnegan wrote:
In this case, the sensor seems to be stuck "on" as if it were receiving
light all the time, so I don't think it's an alignment issue. I verified by
pulling the disk out, checking the LED was working, and playing with the
alignment of the sensor. I got no change in the output according to my
scope.
Moving the disk in and out to block/unblock the light from the write
protect notch let me verify that that sensor was working correctly.
I'm not sure why the index sensors on both
are broken, but not the write
protect notch sensors. Hopefully once the replacements arrive, replacing
that will fix the drives. The drives look pristine on the inside.
The biggest (and most misleading) issue with optical index sensors tends
to be dirt. The phototransistor or LED gets obscured by crud and ceases
to operate, even though electrically, it's fine.
The same phenomenon accounts for many so-called
"alignment" issues with
floppy drives--the track zero sensor gets crud and the position at which
the sensor is interrupted changes. It's a mistake to attempt to
re-align a drive before cleaning the sensor. In reality, most floppy
drives do not exhibit drifting alignment.
The track zero sensor works fine (I could manually move the head and get it
to track back, and the drive doesn't have a spec of dust in it.
As usual my stuff is the atypical case. :)
Pat
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4 comments
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cclist＠sydex.com -
pat＠vax11.net -
vax＠purdue.edu