This page will help you repair DataHand keyboards - if that's too much for you,
then contact me and I might buy they keyboard off
you or else charge to repair it.
The DataHand keyboard is the best keyboard
in the world, period.
I've had two datahands for a couple decades, and sometimes they
need some maintenance. Sometimes, a good
solves the problem, but I've also had keys stop working.
When this happens:
Try a thorough DataHand cleaning. Their
are no components on the board that has the finger keys except
the LEDs and the optical switches, so they can even handle water
directly. I know of one person who puts his in the dishwasher, though
I haven't been brave enough to try that.
Try resoldering the pins on the back of the board. Put a soldering
iron on lowheat and then just touch to the pins until it remelts, it
can take just a couple seconds. This can help if the connection to
one pin has cracked.
If part of a trace is actually broken, it's not too hard to find
the problem with a simple multimeter checking for continuity (and maybe
if you use the diode tester.) That's what the rest of this page is about.
Here's the circuit board for the right finger unit to show you how
everything is connected and how it works. Click on it for a larger image:
Figure 1.1a - The DataHand Finger Circuit Board
Click for full resolution
There's a 14 pin connector on the bottom, I've labelled the pins A-N, with
Diode positive (for two diodes in series)
Switch set 1 positive
Switch set 2 positive
A-K (except E)
Diode ground switch
There are a number of pins that are supposed to be connected to
each other and/or to the 14 pin connector. Use the continuity
tester to see what's broken and simply solder a wire across the two
points to reconnect them - obviously focusing on the keys that are broken.
Each finger board has 20 optical switches (5 for each finger) composed of
an LED/emitter and a switch/receptor. (See bottom of page for photos)
Effectively all of the switches are connected to E on one side (which I've
called "switch ground" though I don't actually know the polarity, and then
half the other side of the switches are connected to "Switch set 1 positive"
and "Switch set 2 positive". Though again I don't know the polarity or the
actual exact specific components used for the switch.
Then the LEDs are paired up and powered in series, all of the positive
being hooked up at L, but each of the negatives hooked up to the 10 yellow
pins. Then the DataHand can cycle through connecting each of the yellow
pins to ground, causing the diodes to turn on two at a time.
For each pair of LEDs, there are the pair of switches, both of them have
one side connected to E, and the other side either connected to M or N.
The operation is something like this: Positive voltage is always applied to "L"
Connect A to ground - this turns on the two LEDs on the far left of
the board (upside down) - these are the LEDs for the right pinky pressing
down or pressing right (the ';' and '\' keys)
Check E->M switch. This tells you if '\' is pressed
Check E->N switch. This tells you if ';' is pressed
Disconnect A. Connect B to ground (turns on LEDs for 'p' and 'n')
Check E->M switch. This tells you if 'p' is pressed
Check E->N switch. This tells you if 'n' is pressed
This is what the switch units look like when you take them off the board: