Latest update: I used lots of 99% IPA and got much (but not all) of the paint off the keyswitches and PCB. I gave up after a while and decided it's good enough.
I found a replacement contrast potentiometer. Its leads are a little too short so it's too loose in the PCB and therefore intermittent, so I may use a regular pot sticking through the hole, which is TBD. I derusted and painted the metal bracket at the top of the keyboard and reassembled everything. Working off a wall wart, it was fine, but when I popped in some batteries, it didn't turn on. I tracked it down to the barrel jack "interlock" failing, so it always thinks there's a power plug inserted. I removed the old barrel jack and installed a new one that is *almost* the right size. I'm going to have to modify the case to get it to fit flush. Two steps forward, one step back, but it's still progress. On Sun, Apr 23, 2023 at 5:37 PM David Plass <dpl...@alum.mit.edu> wrote: > An update: > > Unfortunately there was a freak accident in the workshop... I'm de-rusting > some of the keyswitches and the on/off switch and figured after removing > the rust I'd paint over the rusty areas (it's not ideal, but the best I > could do). > > One of the switches was "clean" so I temporarily installed it on the > keyboard PCB. To paint, I was going to use a silver "paint-pen". While > shaking the pen (according to the directions), the pen exploded and > splattered paint on the keyboard and PCB. About 4 switches were inundated > with paint and another 2 or 3 got some paint splattered on them. > > I spent about a half an hour cleaning the paint as best I could using 99 > IPA, but there's still some paint on the PCB. > > A few hours later I checked some of the affected switches and I think the > paint has dried inside them, because they're open circuits now. I tried > De-Oxit, and they are revived, but I fear it's only temporary. > > My question for the forumbrain is: can the keyboard switches be > disassembled for 'deep cleaning'? I would desolder them first, obviously. > > Thanks > > > > > On Thu, Apr 20, 2023 at 10:48 AM Gregory McGill <arcadeshop...@gmail.com> > wrote: > >> thanks! >> >> On Thu, Apr 20, 2023 at 4:14 AM David Plass <dpl...@alum.mit.edu> wrote: >> >>> I was surprised too but it's a near exact match. I tried the key caps >>> and, while they're tight, they definitely fit. >>> >>> On Thu, Apr 20, 2023, 6:25 AM Louis Ciotti <lciot...@gmail.com> wrote: >>> >>>> I would have never thought these would have been used back when the >>>> M100 was designed. >>>> >>>> Sent from my iPhone >>>> >>>> On Apr 19, 2023, at 10:03 PM, David Plass <dpl...@alum.mit.edu> wrote: >>>> >>>> >>>> The function keys are 12x12x7.3mm tactile switches with square tops and >>>> PCB/through-hole mounting pins. >>>> >>>> For example: >>>> https://www.amazon.com/TWTADE-Momentary-Tactile-Button-12x12x12mm/dp/B07CG7VTGD?th=1 >>>> or >>>> https://www.amazon.com/ACEIRMC-12x12x7-3mm-Momentary-Tactile-Arduino/dp/B091HL5YBD/ref=sr_1_3 >>>> >>>>
