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.richardso...@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 > >
