Hi, I've used alcohol-cleaning of rubber contact and PCB with q-tips, as many suggested already. Then I just wiped a "standard" pencil lead (HB or preferably softer) over the rubber contact. Works for me every time! Tom 2017-11-04 5:07 GMT+01:00 William Levak <wlevak@sdf.org>: > > > I have done this many times. When I was maintaining PETs this was a > constant problem. > > First, clean everything with 91% isopropyl alcohol. > Next, clean the circuit board contacts with a non-abrasive eraser. > > If this doesn't work, then the rubber contacts have shrunk with age. > I then put a small piece of flexible eraser inside the rubber contact so > that it pushes out the rubber contact enough to make a good contact. > > There's no point in trying to measure the conductivity of the rubber > contact. This is a high impedance circuit and takes special equipment to > measure. > > If you have the version of keyboard with the shift lock key, it's a good > idea to replace the two wires going to the shift lock key with longer ones. > You will need to clean these keyboards periodically. > > > > On Fri, 3 Nov 2017, william degnan wrote: > > Hi...I am working on a PET 2001-32B with a bad keyboard. The circuit board >> is OK, the keyboard logic is OK, the computer itself is fine. I have >> isolated the problem to the black carbon tips that touch the circuit board >> upon a tap of a key from the keyboard. >> >> I have cleaned the tips with 91% isopropyl alcohol and that has had little >> effect. I speculate a glaze has formed on the tips and the conductivity >> has been lost. >> >> Should I clean "harder"? >> >> I have heard one should paint/brush a metallic paint onto these tips, but >> I >> am thinking there must be a way to restore the conductivity without adding >> paint, something that will lead to issues down the road. I have also seen >> a page stating the solution is to scribble on the tips with a pencil. >> Also >> not to me a good long-term solution. >> >> Would it make sense to simply use a pencil *eraser* on the tips instead, >> or >> a very smooth sandpaper/file to buff them in order to clear off a thin >> layer/film that may have formed? >> >> I figure someone here has been through this. I searched the web, >> surprised >> to have not have found more written about this. Up to this point I have >> had spare keyboards and this issue never came up. >> >> Thanks >> >> Bill >> >> > wlevak@sdf.lonestar.org > SDF Public Access UNIX System - http://sdf.lonestar.org > > > Message was sent through the cbm-hackers mailing list > Message was sent through the cbm-hackers mailing listReceived on 2017-11-06 11:00:02
Archive generated by hypermail 2.2.0.