Thoughts and info about this unique 80's rubber dome keyboard.

_{Not precision measurements. Angle when flat / Angle with feet extended.
Images are cropped to fit, click to open full view.}

Description

This HP C1405A is a mostly standard 101-key US layout keyboard, equipped with rubber dome over membrane switches. Date of manufacture possibly ranges from 1987 to 1989, according to the date stamps on the internal components. The leftmost keys are stretched by .25 units, making the modifiers slightly wider than usual.

The keycaps are durable 1.45mm thick PBT with dye-sublimated legends, with a unique wide aspect cylindrical profile. The numberpad uses different uniform profile caps, having a sheer drop on the front. F, J and numpad 5 keys all have a deeper cylindrical profile for homing. The primary color for the legends is a deep burgundy, the Alt keys have a much darker purple legend.

Profile view of the deeper homing keys.

Macro shot showing the unique legend colors.

A clever feature is the spring loaded spacebar stabilizer, making the whole spacebar feel a lot more stable. It's just a simple torsion spring wrapped around the stabilizer wire. This also minimizes rattle without needing to use viscous lubricants.

The key mechanism is a basic rubber dome over membrane setup, but with very solid construction. Each plastic barrel is slotted into the 1.5mm thick steel plate, with the function row having individual barrels that can be clipped in and out. This keyboard is clearly designed to be a multi-region product, having around 120 configurable locations for keys. A set of internal switches controls the layout.

Yellow lock lights and internal switches.

Some close shots of the internals while I was deep cleaning the board.

Nearly all the internal components are labeled with "NURI", leading me to suspect that is possibly an internal HP codename for this keyboard.

Thoughts and Opinions

This is my first article that I've written for the keyboard museum, so the layout and methods are subject to change as I figure it out.

From a utility perspective The HP C1405A is an ordinary keyboard, but it stands out with its fantastic style. I'll be keeping this one just because of its unique keycaps. I love the dark purplish red legends, which is something that I've observed on another old HP board. It's quite worn out, the domes in the alpha block feel sluggish. But in places with less usage, like the nav cluster, the domes feel above average I would say. A little silicone lube helped relieve the binding on the Ctrl and Alt keys. If this was in better shape, I would absolutely rotate it into my Model M's place for a while, but unfortunately it's too far gone to feel good to type on.

On top of the unique looks, it's also highly configurable it seems. I haven't tested the dip switches because I don't need to change the layout, but it clearly looks like it could be changed. There are blockers over the windows key locations, which wouldn't have been windows keys at that time of course. In the nav cluster there's more blockers, making me wonder what kind of layout could be configured there. In the default config all the extra keys just output Page Down.

If your computer still has PS/2 ports, you can acquire a passive adapter which converts the 5 pin DIN into the mini-DIN connector for PS/2. It should then work like any old AT keyboard.

I like its quirks, and the previous owner clearly enjoyed using it. It'll now live a cozy life as a display piece I suppose. I have another HP keyboard which will make its way to the museum eventually.

The keycaps are similar in shape to the Olivetti ANK-27 102 N, which can be seen in one of Chyrosran22's videos.