IBM Displaywriter takeapart

[dorkvader]

Cross posted at deskthority:
http://deskthority.net/photos-videos-f8/displaywriter-guts-t7075.html

Ok so I recently got an IBM displaywriter keyboard on eBay. Thanks to all the people that helped me get this once it was found. (The listing didn't say "keyboard" anywhere in the title or description, so it may have slipped past some people's radar.)

Pictures were taken with my galaxy s3 in a moderately lit room, so some are blurry, If you point them out, I'll rephotograph them. Full resolution is on my Flickr, link at the end.

2602678

1982 week 11. Most parts are dated from 1981

Lock key down. This key has no external spring, just the "beam spring". Pushing it down sets a mechanism. Pressing either shift raises it back up. The left shift is "tunable" with a screwdriver. (see later on)


Left shift lock key raise tuning system. The plastic acts as a spring you press against. You can set teh height of the plastic spring by adjusting the nut on the bottom and screw on top


Spacebar stabilizer. I really like this one! the wide plate moves forwards when the stabilizer is pressed. Grease  from IBM is still on the mechanism. (Grease not shown.)


Controller. Closeups showing all the chip labels are on flickr.


Using Webwit's "unique" beamspring naming scheme, we should call this the "IBM Clare Division Keyboard". (Image is of the label on the cable)




OK on to the cool PCB shots!

Notice on this one there are 8 strobes. 4 on each side run the full width of the KB. The need for this becomes apparent when we see the back. The up down alternation is critical to the design. There are 12 sense lines.


Right of PCB. Notice the alternation on the far right function keys.

This is the back, so the far left corresponds to the right of the previous image. Notice they are in parallel! When I first saw this I was at first dumbfounded. That would mean this KB was a low KRO and makes no sense whatsoever. Why did IBM do it this way, when they had a good already established circuit for the rest? Then I flipped it back, noticed the alternation and it all became clear. The alternation is so they can have parallel sense lines for the keys. I do not know how this affects things, but I feel like keeping the sense lines short is a good idea.


Longest sense lines are for the spacebar and keys on that row. They are not paralleled like others. Makes sense to me, though I am only starting to understand IBM capacitive circuits.


Obligatory backlit PCB image. I'll get my roommate to scan the PCB in properly sometime.



Fly plates and associated hardware


Keycaps are cleaning now in a mug on top of the frige.

Ok that was fun. Feel free to ask questions!

edit: corrected sense/strobe terminology.

[Wildcard]

Great tear down and write-up

[Aer Fixus]

Sweet. I really want to understand how the IBM capacitive switches work, especially from a programming standpoint.

[terran5992]

How does it feel?

[Game Theory]

Great and educational photos and write up.

[JPG]

Proud to be Canadian right now seeing this was made in Canada!


Nice find 

[Game Theory]

My 5251 was also made in Canada too.

[CPTBadAss]

Do you have a picture of the whole keyboard and not a closeup shot? I'm curious to see what the whole unit looks like.

[0100010]

Do you have a picture of the whole keyboard and not a closeup shot? I'm curious to see what the whole unit looks like.

Would imagine it looks a lot like this :

[127001]

Great detail shots  , it'll be cool to see when you bring it in your trip.

[mr_a500]

Proud to be Canadian right now seeing this was made in Canada!


Nice find 

Most of the beam spring keyboards were made in Canada. I'm typing this on a Canadian made 3278. It's great that some of the best keyboards ever made were made in Canada. (...by an American company... but that's another story )

[dorkvader]

Great tear down and write-up

Great and educational photos and write up.

Thanks all!

Do you have a picture of the whole keyboard and not a closeup shot? I'm curious to see what the whole unit looks like.

Should be in the flickr album. If not, I'll take another one.

I tried to keep this post to new information that you can't look up elsewhere. There are pictures of DWs elsewhere online (taken by better photographers than me), so I kept them out of the post.

My 5251 was also made in Canada too.

Most beamsprings were, if I recall correctly.

How does it feel?

Close to a selectric, actually. The switches are a little loose and wobbly (due to the old mat inside. I will possibly replace it with something better sometime. Otherwise it's light and clicky, like a lighter model F I Guess.

Proud to be Canadian right now seeing this was made in Canada!


Nice find 

When I visited in 2010, Canada was Awesome!

Do you have a picture of the whole keyboard and not a closeup shot? I'm curious to see what the whole unit looks like.

Would imagine it looks a lot like this :

Show Image

Yep that's it. There's also a version with a 'bigass' enter and a nonsplit leftshift for 2 fewer keys, but it's less common from what I was able to determine.

Great detail shots  :D, it'll be cool to see when you bring it in your trip.

Hopefully the keycaps will be clean by then.

Most of the beam spring keyboards were made in Canada. I'm typing this on a Canadian made 3278. It's great that some of the best keyboards ever made were made in Canada. (...by an American company... but that's another story ;))

My selectric says it was made in NY, and it's still my favourite keyboard, though the beam spring is pretty close. :)

[E TwentyNine]

My selectric says it was made in NY, and it's still my favourite keyboard, though the beam spring is pretty close.

This is a great writeup, thanks.  Regarding the selectric, I had access to them when I was younger and I will never forget, well first the hum of the thing when you turned it on, but more importantly how when you typed when the key reached a certain point it seemed to fall out from under your finger.

Wonder if I could hook one of those up to a computer...

[dorkvader]

My selectric says it was made in NY, and it's still my favourite keyboard, though the beam spring is pretty close.

This is a great writeup, thanks.  Regarding the selectric, I had access to them when I was younger and I will never forget, well first the hum of the thing when you turned it on, but more importantly how when you typed when the key reached a certain point it seemed to fall out from under your finger.

Wonder if I could hook one of those up to a computer...

Yes, they're excellent. I have plans for converting mine with optical sensors (so as not to change the keyfeel), but I have to make sure they're thin enough. An alternative is to put a small neodymium magnet on each typebar and have a hall effect sensor nearby. I have checked and there is enough room for either.

[ch_123]

Did yours have the mechanical latch on the caps lock key?

The "Clare Division" label is almost certainly from the manufacturer of the label as opposed to the keyboard itself. Some of the Model F terminal keyboards also had cable labels (but usually on the inside of the keyboard and not outside). My 3276 beam spring has a handwritten label on the cable with no company name, but the connector has the manufacturer name molded onto the back:

[E TwentyNine]

Yes, they're excellent. I have plans for converting mine with optical sensors (so as not to change the keyfeel), but I have to make sure they're thin enough. An alternative is to put a small neodymium magnet on each typebar and have a hall effect sensor nearby. I have checked and there is enough room for either.

I would really love to see this done.  In the meantime, this will have to keep me occupied.

[mougrim]

Hmm... and how to connect one to a PC? Is it even possible? I know God send to us Soarer, but did he tried to build a converter for beam spring?

[dorkvader]

Hmm... and how to connect one to a PC? Is it even possible? I know God send to us Soarer, but did he tried to build a converter for beam spring?

I think he replaced the controller chip with a teensy, much like what was done with the IBM chinese / japanese (I call them "pingmaster") keyboards.

But Xwhatsit has a prototype controller already that I will want to try and report back on.

[mougrim]

Hmm... If it works, I think you'll write about it here, right?

Anyway, it's an interesting board - and I like shape of keys on it