Replacement switches are available but theyre all 2nd user now, and there are around four different types of keyswitch on a beeb
First thing I'd do (because i always like to start with as much known good as possible) is desolder the offending switches, unscrew one of the pins (one at a time) from the underside of each switch, give them a good clean with wire wool or emerycloth etc, re-insert the pin repeat for the other pin, and then for the other switches. Test them with a multimeter before resoldering them in.
But given that R G V are all on the same column grid I would be suspecting something there, but F, T, 5 and F3 are also on the same column ... do they show the same fault? - if so it could be an issue with the LS45 or the LS 163 on the keyboard pcb - check the circuitry around them
Finally its worth swapping the 6522's ( IC3 and IC69) over as its an easy test as it involves no soldering and just rules out a faulty 6522
First thing I'd do (because i always like to start with as much known good as possible) is desolder the offending switches, unscrew one of the pins (one at a time) from the underside of each switch, give them a good clean with wire wool or emerycloth etc, re-insert the pin repeat for the other pin, and then for the other switches. Test them with a multimeter before resoldering them in.
But given that R G V are all on the same column grid I would be suspecting something there, but F, T, 5 and F3 are also on the same column ... do they show the same fault? - if so it could be an issue with the LS45 or the LS 163 on the keyboard pcb - check the circuitry around them
Finally its worth swapping the 6522's ( IC3 and IC69) over as its an easy test as it involves no soldering and just rules out a faulty 6522
Statistics: Posted by Ukwebb — Mon Dec 30, 2024 8:33 pm