25 Aug
2015
25 Aug
'15
11:25 a.m.
I'll admit to being surprised at the cheapness of the keyboard. Here I
expected to find a true mechanical type, like the early IBM machines - what
I found is a step-down from the C-64.
The switching side is what I'd term a 'membrane sandwich. There are three
layers in the stack, with upper & lower layers forming the switch contact
pairs. Sandwiched in the middle is a perforated insulator sheet, with a
hole pattern that matches the switch contact pattern. Pressing on the right
area of the stack unites the upper & lower contacts, temporarily closing
the switch.
So I suppose if a spilled liquid infiltrated the stack, perhaps drying and
leaving a residue, it may have short-circuited any number of contact pads.
But IIRC, I was measuring +very+ low resistance in the shorted pins. I'm
not sure how even dried Coca-Cola could create that hard of a short.. so I
need to take some more careful readings. If they are truly hard-shorted,
I'd tend to look for something other than a contamination issue.
On Tue, Aug 25, 2015 at 6:52 AM, Jules Richardson <
jules.richardson99 at gmail.com> wrote:
On 08/24/2015 09:13 PM, drlegendre . wrote:
On the bright side, I may be able to send you
some bootable media, if you
still need it.
Thanks for the offer, but I definitely have it somewhere - I'm just not
sure where! Eventually I'll have the PC set up to write images again anyway
(I'm just reorganizing my work/storage space at the moment so it's a bit of
a disaster area)
I figure I'll go the solvent flush route, using tri-chlor, and see where
that goes. But honestly, I don't know what
could be causing so many
'stuck'
keys on this thing!
Do any of the keys feel different? I assume there's a sponge pad on the
bottom of each key to produce the right feel when the key is pressed - I
wonder if something's been spilled in yours at some point, and some of
those pads have expanded and/or gone hard... although I suppose it could
just be age-related deterioration.
As ever, my fear is that the materials won't withstand the solvent, even if
it's tri-chlor, and I'll end up washing
away every hope of survival. Water
might be OK, but I'd have to grab a couple gals of distilled first.
Well, if there is sponge in there and it's gone bad then I suppose opening
the thing up is the only solution anyway :(
Ultimately, the dreaded R&R is the option. Not sure if I have the
patience...
Yup, it'd certainly be a job. Unfortunately I don't have the contact info
for the guy who took the third one of these machines, but I suppose he may
surface on the list at some point. It's possible that machine was snafu in
such a way that there might be a surplus keyboard available...
cheers
Jules