Advice on repairing an SGI granite keyboard with dented PS/2 plug

glaurung · 15 Apr 2018, 22:15

I have an SGI 9500900 "granite" keyboard. The plug looks OK, but I cannot get it to plug in properly without a ton of wriggling and fiddling and a scary amount of force. I've tried plugging it into a couple of different PS/2 ports and adapters, they all are problematic. I can just barely plug it into the SGI Indy that it came with (yes I bought a vintage workstation just to get the bundled keyboard. I need professional help). Most of the other PS/2 ports I've tried to plug it into, I flat out can't make it work, or it plugs in but doesn't feel secure and some keypresses don't register when I type on it.

Every time I try plugging the keyboard in, I am terrified I will bend one of the pins or otherwise ruin the plug. I don't want to get involved with hand wiring a new plug because that will look crappy and I will have trouble selling it on if/when I find a keyboard that suits me better.

Does anyone know of a source for compatible replacement cables? Anyone know how tricky it is to replace the cable on these keyboards?

fohat · 15 Apr 2018, 23:15

Have you tried using a small pair of needle-nosed pliers to gently ensure that everything is properly aligned?

If the outer ring is no longer circular, make it so.

glaurung · 17 Apr 2018, 06:02

I've looked carefully and I can't see any deformations - like I said, it looks normal, whatever is wrong with it is too subtle for me to see.

gondol9 · 17 Apr 2018, 06:04

In my experience with PS/2 connectors its typically corrosion on the pins that is the problem. There's not much you can do because theyre so delicate, other than try to scrape it off with a razor blade, and if that fails attach a new connector.

glaurung · 17 Apr 2018, 08:36

I figured out what was wrong with it - missed seeing it the first five times I looked at the damn thing. The outer ring is splayed out so it's bigger around than it should be.

I tried fixing it with pliers, no dice - it's now bent out of shape worse than it was before.

Unscrewed the case and was pleased to discover that it's a lot less finicky inside than a Model M. I have the detached cable.

Where can I find a PS/2 cable with this type of connector, and how standardized is the wire arrangement for a early to mid-90's keyboard?

Anakey · 17 Apr 2018, 10:16

most of the keyboards should have that style of internal connector, it might be a case of swapping the plastic housing over so it would fit but the same arrangement of wires should be available

zool · 17 Apr 2018, 10:57

glaurung wrote: ↑I figured out what was wrong with it - missed seeing it the first five times I looked at the damn thing. The outer ring is splayed out so it's bigger around than it should be.

I tried fixing it with pliers, no dice - it's now bent out of shape worse than it was before.

Unscrewed the case and was pleased to discover that it's a lot less finicky inside than a Model M. I have the detached cable.

Where can I find a PS/2 cable with this type of connector, and how standardized is the wire arrangement for a early to mid-90's keyboard?

That looks like a 7x ~1.5mm pitch JST connector. measure the spacing between pin centers. There are quite a few variants of the JST. JST is pretty popular, but getting the exact pinout might be very tricky. you might have to splice inside the case.

http://www.jst-mfg.com/product/pdf/eng/ePH.pdf
maybe better match
http://www.jst-mfg.com/product/pdf/eng/eXH.pdf

Anakey · 17 Apr 2018, 11:04

zool wrote: ↑
That looks like a 7x ~1.5mm pitch JST connector. measure the spacing between pin centers. There are quite a few variants of the JST. JST is pretty popular, but getting the exact pinout might be very tricky. you might have to splice inside the case.

It would be quite easy though to remove the individual wires from a different connector and then put them into the original connector if it were a different pin spacing etc. The silver prongs that you can see on the side of the connector in the above image can be pushed in with a screwdriver at the same time pulled from the back of the connector and the wires should come out of the plastic housing.

zool · 17 Apr 2018, 12:01

Anakey wrote: ↑
zool wrote: ↑
That looks like a 7x ~1.5mm pitch JST connector. measure the spacing between pin centers. There are quite a few variants of the JST. JST is pretty popular, but getting the exact pinout might be very tricky. you might have to splice inside the case.
It would be quite easy though to remove the individual wires from a different connector and then put them into the original connector if it were a different pin spacing etc. The silver prongs that you can see on the side of the connector in the above image can be pushed in with a screwdriver at the same time pulled from the back of the connector and the wires should come out of the plastic housing.

true, the crimp is no to bad to do either if you cant find a cable.

glaurung · 17 Apr 2018, 14:55

It would be quite easy though to remove the individual wires from a different connector and then put them into the original connector if it were a different pin spacing etc. The silver prongs that you can see on the side of the connector in the above image can be pushed in with a screwdriver at the same time pulled from the back of the connector and the wires should come out of the plastic housing.

Yeah, I've rewired the front panel headers on a PC before when I had a three prong connector for the power switch and everyone had switched to a two prong standard. And I've found someone over on geekhack who has figured out the order of the wires that SGI used. So now I just need a new cable with the right connector. Hopefully without paying a fortune in shipping to Canada. Thanks guys for ID'ing the connector and making suggestions.

Blaise170 · 17 Apr 2018, 15:12

Instead of shipping a cable into Canada, look for PS/2 boards near you. You should be able to find a cheap rubber dome board for less than $10. Then you can just rewire that.

glaurung · 17 Apr 2018, 15:25

Having poked around Google I think the best option is to find a cheap PS/2 keyboard near me and buy it for the cable. Which sucks in terms of environmental responsibility.

But AFAIKT, nobody except Unicomp even bothers listing replacement cables for sale (FYI, if you need a new PS/2 cable, Unicomp will sell you one for $15 US - just feed them a model M part number). And I know from experience that unicomp will want more in shipping than for the $15 cable.

Being Canadian is great in many ways but having to pay shipping from the US sucks massively.

mike52787 · 17 Apr 2018, 15:30

Go to some local thrift stores, the odds of you finding a crappy old ps2 rubberdome are good.

Blaise170 · 17 Apr 2018, 15:47

In terms of the environment, it sucks but swap the cables, then donate the cheap one back to the thrift store. Let the next buyer figure it out.

glaurung · 19 Apr 2018, 21:49

I scored a free PS/2 keyboard - a Microsoft Basic 1.0A. If you live in Toronto, Above All Electronic Surplus near Bathurst and Bloor is a great place to visit for your obsolete tech needs.

Now for the sucky part - I have to determine the Microsoft's wiring arrangement. Googling has not helped me. If I wire this sucker wrong, will I smoke/kill my computer and/or the keyboard, or will it just not work?

The Microsoft has five wires - Black, Red, Black, White, Brown. The PCB doesn't have any indications printed on it that I can see.

Any advice on matching that up to the SGI pinout, which I've learned is:

Yellow - Clock
Black - Data
Red - No connection
White - Ground
Green - VOC
Black - Chassis Ground
Black - Chassis Ground

(see https://geekhack.org/index.php?topic=53 ... msg1205278 )

Blaise170 · 19 Apr 2018, 21:52

The only way that I can think of is to use an multimeter and touch it to a pin and then to each wire to see which one gives you continuity. That would be easiest I think anyways. Then you can match up the pin/wire combo to the appropriate pin on the SGI.

P.S. That might be a bit hard to follow, I'm going to sketch up a quick diagram.

Blaise170 · 19 Apr 2018, 22:04

Okay so in the example below, you would need to rewire the PS/2 connection on the MS such that:

Purple -> Red
Yellow -> Orange
Blue -> Yellow
Orange -> Green
Red -> Blue
Green -> Purple

If you rewire such that the wires are in that order, it should be "plug and play" since you are literally just using the same wires from the same pins on the PCB. Note that the colors are completely made up so you'll still have to test continuity yourself.