Take around three bristles from a small wire brush and chuck them in a pin vise or razor knife holder. Trim their ends even. Place a drop of 91% isopropyl alcohol in the hole behind the offending key and gently "scritch" around in the hole with the wire brush. Be careful not to break a bristle off in the hole. This also works for HP41 keys. If possible, avoid breaking the posts. If you need to cut them, try to do it in a manner that allows for subsequent glueing or otherwise sealing them when you are finished.
1818-0550, 1881-0551, 1818-0231, 1818-0232
ROM/RAM ICs
-----------
Vss--| U |-- Sync
Phi_2 --| |-- ISA
Vgg --| |-- Gnd
Phi_1 --| |-- Data
-----------
Vss, Vgg : Power supply
ISA : Instruction and Address
Sync : System bus sync input
Phi_n : 2 phase system clock
Each chip contains ROM and 16 7 byte registers, so a total of 64
registers in the machine. 32 of them are used for 32*7 = 224 bytes
(steps) of user program memory). The other 32 registers form the 26 user
register (P0-P9, S0-S9, A-E and i), the 5 stack registers and one
register containing the user flags, angle mode, decimal setting, etc.
ROM/RAM ICs
-----------
Vss--| U |-- Sync
Phi_2 --| |-- ISA
Vgg --| |-- Gnd
Phi_1 --| |-- Data
-----------
Vss, Vgg : Power supply
ISA : Instruction and Address
Sync : System bus sync input
Phi_n : 2 phase system clock
Each chip contains ROM and 16 7 byte registers, so a total of 64
registers in the machine. 32 of them are used for 32*7 = 224 bytes
(steps) of user program memory). The other 32 registers form the 26 user
register (P0-P9, S0-S9, A-E and i), the 5 stack registers and one
register containing the user flags, angle mode, decimal setting, etc.
