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Druid6900
March 8th, 2009, 07:31 PM
Ok, I have a couple of Model M keyboards (both are 1391401s, one from 91 and one from 92) and both have the detachable cables.

Now, one of the cables terminates in the standard PS/2 mini-DIN with the 6 pins and center plastic locator.

However, the other has only 4 pins (although the other two holes are there) and it doesn't look like the two missing pins have broken off, because there are no stubs in the holes. The center locator is likewise missing but it appears that nothing has ever been glued into the hole for it.

Is this a standard connector configuration for something?

chuckcmagee
March 8th, 2009, 07:48 PM
http://pinouts.ru/Inputs/KeyboardPC6_pinout.shtml

Yes, I know. "Something new every day". Which is good, keeps us from getting bored.

Turns out, the beloved PS/2 connection really only uses 4 wires. Other 2 are just noise.

Druid6900
March 8th, 2009, 07:58 PM
http://pinouts.ru/Inputs/KeyboardPC6_pinout.shtml

Yes, I know. "Something new every day". Which is good, keeps us from getting bored.

Turns out, the beloved PS/2 connection really only uses 4 wires. Other 2 are just noise.

Yup, those are the pins that are missing, and I never even thought to look up the specs on the connector.

Thanks for the assist, Chuck.

Allen
March 8th, 2009, 08:18 PM
Although I'm not 100% sure of this, later cables for Model M keyboards (in particular attached cables on IBM part numbers 52G9658, 52G9700, 82G2383, and others) contain only 4 pins rather than 6 pins on the mini-DIN end of the cable because of cost reduction measures resulting from pricing pressures in manufacturing keyboards in the U.S. As stated by Chuck, only four of the pins are used in the 6-pin mini-DIN configuration for the keyboard signal. So why bother wasting any more gold and other metal to provide two useless pins? I make this inference because Lexmark made numerous design changes to the Model M keyboard to reduce costs (see http://findarticles.com/p/articles/mi_m0EKF/is_n1891_v37/ai_11677212). Reducing the number of pins on the connector may have been one of them.

And since you bring up the topic, for self-promotion and to promote and encourage everyone to use the Vintage Computer and Gaming Marketplace, I have many of these SDL to PS/2 cables for Model M keyboards for sale (with 6 pins): http://marketplace.vintage-computer.com/100090,owner_id,other_items.

Ole Juul
March 8th, 2009, 09:11 PM
Nice bunch of kbds for sale there Allen. I was interested to see three different chord sets and they all have the same problem for me. I've got a bunch of Ms and some chords but what I really need is a chord where the SDL has at least a foot of length before it goes curly. Better still one that isn't curly. Does anyone know the whereabout of one of these or (best of all) where I can get an SDL plug to make my own chord?

The problem I've got is the curly part is too bulky and gets in the way all the time. I like to put a couple of papers and stuff just behind the kbd. Also, I have an allergy to curly chords. :)

chuckcmagee
March 9th, 2009, 10:42 AM
Of course, the extra pins and especially that rectangular piece of "key" plastic really added strength to the connection. I can't count the number of times my various PS/2 cables have popped off the back of the computer, or bent over sideways.

MikeS
March 9th, 2009, 11:39 AM
Turns out, the beloved PS/2 connection really only uses 4 wires. Other 2 are just noise.
---------------
Not always; some systems (notably IBM Thinkpads) use the extra 2 pins for mouse data & clock.
http://pinouts.ru/InputCables/Ps2KeyboardYThinkpad_pinout.shtml

Chuck(G)
March 9th, 2009, 02:21 PM
---------------
Not always; some systems (notably IBM Thinkpads) use the extra 2 pins for mouse data & clock.
http://pinouts.ru/InputCables/Ps2KeyboardYThinkpad_pinout.shtml

Didn't some versions of the Model M also include a speaker (PC RT maybe?)? That might make those pins useful.

Ole Juul
March 9th, 2009, 02:56 PM
I've taken apart a couple of Ms and there was no speaker, but there was clearely a place for one.

Allen
March 9th, 2009, 05:44 PM
There is another style of IBM branded SDL to PS/2 keyboard cable in addition to the three I have listed; the other style can be seen here: http://marketplace.vintage-computer.com/101967,auction_id,auction_details. There are also a number of SDL to AT keyboard cable styles (with and without the IBM logo). Still, I have never seen any of these SDL to PS/2 or AT keyboard cables without the coils, though I have seen other SDL cables without the coils (like SDL to SDL). I'll let you know if I come across any SDL keyboard cables without the coils.

Ole Juul
March 9th, 2009, 10:20 PM
Thanks Allan. This is not a "vintage" situation so brand doesn't matter. Like I said just getting a plug would be the best solution. I didn't want to destroy any of my vintage cables, but perhaps I should buy another one and just do a splice. I see the price is many times lower than they were originally.

Allen
March 9th, 2009, 11:00 PM
If you want to make a cable (and have the know how and tools to do it), then I suggest you take the cable from any PS/2 keyboard (like one from an electronics recycler) and connect it to an SDL connector like this one: http://www.newark.com/jsp/search/productdetail.jsp?SKU=33B9296. I don't think it's necessary for you to get an actual SDL to PS/2 or AT cable, since they are all coiled apparently.

You shouldn't have any problems finding an unwanted PS/2 keyboard locally (for the cable), but if you can't seem to get an SDL connector, let me know, and I will get you one of those SDL to SDL cables (I can probably get those for little or no cost locally). Just let me know no later than 10 days.

Ole Juul
March 10th, 2009, 01:16 AM
Thanks Allan. No, I have no problem making cables, I've been doing that stuff since the 50's. What I didn't know is that SDL connectors were available now. I last looked about 10 years ago and couldn't find any. Now you show me differently. I just did a search (DOH!) and there seem to be several suppliers but mostly large quatities or relatively expensive. Still, under 10 bucks is worth it to me. The SDL to SDL cable you mention sounds good, I'll let you know if that's the best option. Thanks for the tip!