My IBM Model M has weird dangly bits

[doctorpiorno]

Hi all,

This morning I was lucky enough to bump into a Model M during a morning visit to the Rastro (a massive flea market in Madrid) and decided to buy it on the spot as a late Christmas pressie for a friend, with a view to convert her to the Cult of the One True Keyboard. The label on the bottom is worn away, so I don't know what vintage it is, but it seems to be in good condition and tested fine on my computer. Yay!

I did come up with a surprise when I started stripping the keytops away for the routine cleansing ritual, though. Unlike any other Model M I have laid my eyes on, this one has some sort of cable attached to the spacebar. I don't dare crack open the case to investigate where it goes, but it seems to disappear below the black plastic layer that separates the keytops from the PCB. On the other end, it's connected to a little piece of copper attached to the underside of the spacebar. See attached pics for reference.

I'm not overly worried about it being there, but I'm curious as to what its purpose might be. Has any of the Model M historians in this forum seen something like this before? Any clue what its purpose might be?

Thanks in advance for any info and merry Christmas to everyone!

[bhtooefr]

Why not crack open the case? It'll allow you to clean the keyboard better, and there may be further identification underneath. The odds of causing damage aren't high if you don't do anything stupid (like expose the controller to ESD or something.)

I'm seriously interested in what this thing is.

Anyway, we'll work with what we've got...

Color of IBM logo: Is it white with blue lettering, white with gray lettering, or metal with black lettering?
Drainage holes: Are there four drainage holes along the front?
Cable: Is it detachable? If so, AT or PS/2?
Speaker: Does it have one?

[lam47]

My one has it. 1992 UK grey logo on the left detachable cable.
It is bolted to the metal plate.

[doctorpiorno]

Why not crack open the case?

I'm tempted to, but I'll be giving it to the lucky recipient tomorrow and I'm afraid I won't be able to put it back together quickly enough if I tinker with it too much. Besides, I'd be surprised if I managed to find an allen wrench of the appropriate size on a Sunday evening in Madrid.

More details: the logo is blue lettering on light grey. No drainage holes. It does have a speaker grille, but no speaker that I can see. It definitely didn't make any sound other than the usual clicky goodness when I tested it. The cable is PS/2 and detachable. Keytops are two-piece.

This is a European Spanish layout keyboard, by the way (¡ýáý! ¡fúññý éúrópéáñ çháráçtérs!), so I'm not how sure serial numbers correlate to the US-manufactured Model Ms. Most of the ones we got over here were UK-made.

[bhtooefr]

OK, sounds like something IBM UK did, and seems like it's for grounding... but why?

[lam47]

It could be something to fo with the UKs obsession with grounding everything.
We still use a 3 pin mains socket here but for years most electrical goods have only used the live and neutral. Time was everything used the earth pin too.
Although earthing a plastic space bar is nutty even for us Brits.

[bhtooefr]

But see, almost all outlets in the US have been three-pin for years, and lots of stuff is grounded here.

And we don't have grounded spacebars.

[lam47]

I thought the US used a 2 pin plug? or am I thinking of Japan?

[Chloe]

The Keytronic KT2001 has a grounded space bar:
http://www.keytronic.com/home/products/specs/euro_kt2001.htm

[bhtooefr]

Well, if an appliance only uses 2 pins, that's usually how many pins are on the plug, but the grounding pin is on almost all outlets nowadays.

All desktop computers use 3 pins, for example.

[Busty]

I think the ground at the space could be related to the metal bracket and that it could act as an antenna for static charges on the plastic. In some lab environments they are close to paranoid when it comes to static charges on moving plastic parts and potential outlets for that.

[lowpoly]

I have one of these space bar wires too. German Layout, blue logo.

[sandy55]

Mine is '96 UK Greenock with blue logo. grounding wire is clipped to base plate ( not bolted ).

see keyboard details here

[keyb_gr]

To add one more twist, apparently there are space bars with only two support braces around as well (Sandy's pics above show ones with three). They appear to be interchangeable with the others, just swapped them around for a test. My 1991 M had the two braces version (otherwise similar to the lower one on Sandy's picture) and no grounding, while the 1989 and 1993 samples have the regular version (upper one in Sandy's pic) plus grounding.

The 1991 sample also has a slightly rougher key feel (must be due to actuator panel, not keys themselves), which leads me to think that maybe it was destined for a lesser model PS/2. Otherwise they're all 1391403s (German layout) made in Scotland. The newer ones both have print 08A stated on the label but one is build 94A and the other 81C (the latter is the only one to have drainage holes as well).

Grounding the space bar is most probably not rooted in an obsession for grounding everything. I'd rather guess that it was intended to drain off static charges to keep people in dry environments (think air conditioning) from getting zapped when subsequently touching any grounded parts like the computer case, and possibly to protect the keyboard's and mouse's electronics as well. The space bar is about the first thing you touch. ABS plastic may not be terribly conductive, but a few megohms generally will do.