Rodney said:
Compaq Presario 2504EU has a constantly repeating u key. I've removed
the key top and the scaffold thing below so that I can lift the rubber
and get to the contact below. I've cleaned the contact area and rubber
with iso propyl alcohol and the key stops repeating. However once it
dries it starts to repeat again.
It also has a problem with the drive interface, it will only run in PIO
mode (following a close lightening strike) so is very slow. I don't
think it's not worth replacing the keyboard.
Any suggestions or ideas?
Drives can be down-shifted into PIO transfer mode,
as a means to "restore reliability" to the interface.
The idea is, if a drive is throwing CRC errors,
the Windows driver slows it down, thinking the read
error rate will be reduced.
This is a concept copied from Unix, which does
the same thing for SCSI devices.
They have a "Fixit" file here, for that. As well
as some Regedit you can try.
http://support.microsoft.com/default.aspx?scid=kb;en-us;817472
Depending on your luck, that might be easy to fix.
*******
I don't have a solution for the keyboard. Keyboards are
relatively high impedance circuits. The keyboard I built
as a hobbyist, from scratch, the scan matrix used 100K
impedance signals. A bit of surface leakage, might cause
a key depression to be detected. And being a scan matrix,
more than one key sits on a scan line. Some keyboard
chips used a 17x7 matrix of row and column lines.
Pulses go out on one set of lines (each line is pulsed
one at a time), and the detection lines look for the pulses
as proof one of their keys have been pressed. I don't know
how I could "condition" the signals, to stop a problem
from showing. Even if you drilled out the two pins
or connections to a row and a column line, the leakage
could be elsewhere underneath the keys. Like, carbon
scoring from an arc or something. You'd think if that
happened, the keyboard chip would have burned out...
You could clean the entire keyboard PCB, but that would
be "above and beyond the call of duty". Maybe someone
will have parted out a similar machine on Ebay, and
you can get another keyboard there. On some laptops,
there are four or more different part numbers for keyboards,
so you have to be very careful, to get exactly the
right one for your machine. Each part number, would come
with a different set of keycaps and relevant encodings.
(Like a German or French keyboard maybe.)
Paul
