oh dear f***ing god. an LK201 keyboard is the most evil unmaintainable piece of equipment DEC ever put out; It was followed by the mostly-backwards-compatible and more tolerable LK401 keyboard (which doesn't fail QUITE as often and is not QUITE as irrepairable from what I've been told). It has an unusual propensity for spontaneous failure, and the entire inside is held together with melted plastic spikes, making it impossible to disassemble and repair. The membrane (it is one of the earliest 'open membrane' (read: cheap) keyboards made is held permanently bent (unlike the membrane in an ibm/lexmark model M keyboard, which despite being clicky does use a membrane, but one held perfectly flat), causing it to wear out unusually quickly from constant stress on the plastic; also holding keys down for an extended period of time by something sitting on top of the keyboard will cause the membrane layers to weld themselves together causing stuck keys, which because of the plastic spikes is impossible to fix. Not to mention that the keyboard mcu will fail its power on self test and refuse to work if any keys are stuck down, rendering the keyboard an obscene giant paperweight.
to make matters even MORE fun: the way the membrane is attached to the pcb with the MCU on it is using these metal one-piece clamps, which make it almost completely impossible to remove the membrane without damaging it further (you have to sort of shove part of a credit card in between the membrane and the contact spikes, them yank the membrane out hopefully not scraping off the contact layer on the credit card!)
There are two versions of the LK201: one has red LEDs and has an Intel MCS-48 series MCU, and the other has green LEDs and has a mc6800-series (or maybe Hitachi 6300-series) MCU; the clock crystals used on both versions are different.
I have a damaged/irrepairable LK201 of some variety here, as well as two working ones, one with red LEDs, and one with green LEDs.
No offense is intended to rainbow_will by this post, I just can't stand the rampant reliability issues with lk201 keyboards; fortunately there seem to be quite a lot of them out there so getting spares is not a major deal yet.
The lk201/401 is used by, at least:
The vt520 does not use it; it uses a plain ps/2 keyboard.
Although a special VT520 PS/2 keyboard with extra DEC keys is what you're supposed to use with it, it will work fine with any PS/2 keyboard.
Last edited by Lord Nightmare; 02/27/12 12:03 AM.