These both work.
https://www.digikey.com/en/products/detail/cui-devices/DS04-254-2L-04BK/11310925
https://www.digikey.com/en/products/detail/w%C3%BCrth-elektronik/418127160904/5208901
It's annoying how tiny the actuator is, but I couldn't find any that
were short enough yet had big actuators like the TPDD1 has.
Definitely if there is anything wrong with the pressure pad it won't
work, though I'm not sure if the drive would give an error code that
means communication error in that case. It might.
You can verify your cable is ok with a DMM and the table here
https://github.com/bkw777/TPDD_Cable?tab=readme-ov-file#standard-wiring-for-a-model-t-like-the-original-cable
The 2nd table where is says "to verify the final result..."
IE: For drive pin 1 to db25 pin 7, put the meter in continuity-tester
mode so it beeps, put the black lead on pin 1 on the drive end, and the
red lead on db25 pin 7, and it should beep
For for drive pin 3, put the meter in diode mode, put the black lead on
pin 3 on the drive end, and pin 6 on the db25, and the meter should read
about 1.7v +- 0.1v is close enough.
Repeat for the rest of the table.
If you have a linux machine or are willing to boot up a linux thumb
drive, you can use pdd.sh to interrogate the drive with more control
than what TS-DOS provides. It's supposed to work on mac too, but I think
I may have borked it on mac recently and I think there is some kind of
timing issue. It used to work so I guess you could just use an old git
commit, though I don't know how old to suggest other than sometime last
year. Don't bother with WSL or cygwin.
https://github.com/bkw777/pdd.sh
There are a lot of commands and a lot of things not fully explained in
there so I'll give some more explicit directions if you want to try it.
I have one FB-100 clone (Purple Computing) that exhibits similar
behavior and in my case 2 things.
1: The hub that grabs the disk was cracked near the metal shaft and
allowed to spin on the shaft. Super glue fixed that.
2: I think either the index optical sensor or it's led is dead.
I haven't finished diagnosing this drive yet but the board is all
working fine, but I have multiple drives and have swapped parts around
to prove that the board is good with a good mech, and the drive
mechanism is bad even on a good board, even after fixing the hub and it
is definitely no longer movable on the shaft. And the error code that
the drive gives is actually 0x82 'Abnormal Index Signal' or 0x80 'No
Index Signal' I forget which but one of those.
I was able to see that actual error code from pdd.sh, and do other
things like simply verify that the the motherboard and cpu and serial
communication were all solid just by being able to issue commands and
get responses as long as they didn't require the disk to spin, and see
every byte of the actual traffic back and forth.
The index pulse is read from the same hub that I glued, and that whole
area would kind of trap the glue vapors, so it's possible the superglue
vapors fogged up the led or the sensor, or it's possible the led or the
sensor just happen to also be bad, and it's just a coincidence that both
of those problems would result in the same error code.
I'm still in the process of working on that drive but along the way in
case you need it, I found the connector to match the ribbon cable to
exercise the mechanism using the existing cable the same way the
motherboard would:
https://www.digikey.com/en/products/detail/molex/0039532095/3160258
And the closest approximation of the sensor is:
https://www.digikey.com/en/products/detail/rohm-semiconductor/RPI-441C1E/2408204
The sensor will require some destructive hacking to get in there since
the original has a different plastic body. It's part of the reason I'm
bothering with rigging up a breadboard connection to the ribbon cable to
prove what the problem actually is before trying to butcher up some
other kind of sensor. I could just tack wires directly to all the
sensors and leds but I want to test the whole cable anyway.
On 5/19/24 09:08, Scott McDonnell wrote:
The jumper is indeed missing. If someone wants to install one, they will
need a very low profile switch. I got what I thought was pretty low
profile, but it was just slightly too tall.
But I didn't care much that I couldn't put the switch cover back on so I
left it that way.
-------- Original message --------
From: [email protected]
Date: 5/19/24 8:20 AM (GMT-05:00)
To: [email protected]
Subject: Re: [M100] FB100 disk communication error
I seem to recall there was something different on the FB100. Like the
dip sw was missing so you have to jumper it out so it uses the correct
BAUD rate.
Jef Birt
*From:*M100 <[email protected]> *On Behalf Of *David Plass
*Sent:* Saturday, May 18, 2024 6:36 PM
*To:* [email protected]
*Subject:* [M100] FB100 disk communication error
I recently got a FB100 disk drive. I disassembled it to check the belt,
which seemed...okay...
I didn't put it all back together (fool me once, shame on you...) On my
T102 with TS-DOS (in ROM), it recognized the drive. I put in a disk
(DSDD) and TS-DOS said "not-formatted", as expected. So I formatted, but
after crunching for a while it said "Communication error". I tried with
another DSDD disk that I formatted on my laptop and it had the same result.
Since I hadn't reassembled it completely, during the format, I could see
the head moving so I knew at least the signalling was working. Also,
possibly significantly, during the format it seemed that the upper pad
arm (opposite the read/write head) wasn't touching the disk.
Is this normal?
More background: after the partial reassembly, I tried inserting a disk
and it didn't slot in, and I may have pushed a little too hard. Turns
out somehow the upper pad arm shaft was stuck under one of the metal
tabs of the "disk holder assembly" so there was no way for a disk to go
in. After fixing its location, I was able to easily insert a disk.
Could the upper pad arm be misaligned, causing the communication error?
Or could it just be an old belt, causing timing issues on the motor?
Any additional debugging tips would be appreciated.
(https://archive.org/details/tandy-portable-disk-drive-service-manual-26-3808/page/n4/mode/1up
<https://archive.org/details/tandy-portable-disk-drive-service-manual-26-3808/page/n4/mode/1up>
is my reference.)
--
bkw
