Build quality of the IBM Model M 1391401 keyboards from 1987-1992

[mac80211]

Hi,

I was just wondering if there are differences of the model m 1391401 keyboards made from 1987-1992 as far as build quality and weight are concerned?

[XMIT]

Yes.

The differences are documented at length here:
wiki/IBM_Enhanced_Keyboard

[mac80211]

thanks.

[andrewjoy]

We should also mention that there was also a slight overlap of the model F and model M design.

Take a look at the model M50 key,



As you can see thats a model F top and bottom plate right there with a model M membrane inside it.

This is clearly a first attempt at cost reduction at the early stage of the model M development.

I like to refer to it as a proto M, would love to try one some day.

[clickykeyboards]

Some additional observations

Model M keyboard weights (1986 - 2003) http://www.clickeykeyboards.com/model-m ... 1986-2003/

Model M keyboard weights (1986 - 2003) (with cables), Original research by ClickyKeyboards

model-m-weights-wcables.jpg (255.83 KiB) Viewed 7207 times

[andrewjoy]

Do you have any data on the weight of the sliver label 102 terminal Ms ?

Its ether a 1386303 or 1386304

[seebart]

Good question that's been answered now. I recently got a 1390148 from 1986 but I doubt there is any difference in build quality to my 1390133, I'll have to check.

IMG_20160822_125224.jpg (708.46 KiB) Viewed 7186 times

[andrewjoy]

that does not happen to be 16/07/86 does it ?

[seebart]

that does not happen to be 16/07/86 does it ?

Nope, sorry.

IMG_20161011_173129.jpg (868.69 KiB) Viewed 7172 times

I'm planing a screw-mod for it, I managed to tear up the barrel but I'm getting a replacement barrel from 7bit.

[mac80211]

Some additional observations

Model M keyboard weights (1986 - 2003) http://www.clickeykeyboards.com/model-m ... 1986-2003/

model-m-weights-wcables.jpg

Great! thanks!

[kalrand]

We should also mention that there was also a slight overlap of the model F and model M design.

Take a look at the model M50 key,



As you can see thats a model F top and bottom plate right there with a model M membrane inside it.

This is clearly a first attempt at cost reduction at the early stage of the model M development.

I like to refer to it as a proto M, would love to try one some day.

Do you know if the M50 uses M or F pivot plates? I would assume M.

[micrex22]

Do you know if the M50 uses M or F pivot plates? I would assume M.

M; using F pivot plates wouldn't hit the M membrane where it needs to be. Same applies vice versa even if we were to assume M pivots were carbon impregnated.

AFAIK nobody has used Model F springs in a Model M assembly, they may or may not be too soft to be able to actuate against the membrane properly. It would be fun to try M springs in a Model F for science.

[andrewjoy]

It will use all M inside but the top and bottom plate are model F .

The springs are different so they would not work. M F and M2 springs are all different .

[emdude]

Is this true? This GH thread says that if you switched springs on an Model F flipper, the difference in feel between Model M and F springs is not significant enough to be noticeable.

[drevyek]

A visual inspection of M and F springs shows them to be pretty similar (XT vs '1401 from '92). Same length, same radius of coil, same number of turns. There may be material differences though.

[fohat]

A visual inspection of M and F springs shows them to be pretty similar (XT vs '1401 from '92). Same length, same radius of coil, same number of turns. There may be material differences though.

Here is the photo that I took:

[micrex22]

Is this true? This GH thread says that if you switched springs on an Model F flipper, the difference in feel between Model M and F springs is not significant enough to be noticeable.

Model M springs have less coils and as a result are more stiff; that's a scientific fact. The more coils you have in a spring the easier it is to compress. The whole reason why Model Fs feel so different is the fact that the rubber mat is gone and the springs have more coils...

That GeekHack thread is sadly a heavy dose of misinformation.

[y11971alex]

One thing that I noticed today was that my Model M feels so much smoother when I replaced its caps with some from my Model F.

[micrex22]

One thing that I noticed today was that my Model M feels so much smoother when I replaced its caps with some from my Model F.

There's a lot of little differences in Model M and F key tops; I should probably do a write-up of all of these differences (since I am aware of it and have a lot of examples to show it off). After the 'great retooling' of 89', some of the keycap molds had curious ridges around the top / I'm fairly fond of it since it feels neat under the fingertips:

You will notice them prominently on M, K and L. Whereas key tops like N and H are 'normal'. This was not a thing prior to '89 and the '89 keycaps have a lot more texture to them, the texture on them is different from early Model F key tops, even. I could even go on about the differences in the unicomp key top textures but again that's probably going too off topic and deserves its own thread some day...

[emdude]

Is this true? This GH thread says that if you switched springs on an Model F flipper, the difference in feel between Model M and F springs is not significant enough to be noticeable.

Model M springs have less coils and as a result are more stiff; that's a scientific fact. The more coils you have in a spring the easier it is to compress. The whole reason why Model Fs feel so different is the fact that the rubber mat is gone and the springs have more coils...

That GeekHack thread is sadly a heavy dose of misinformation.

Yes, I was aware that Model F springs should have more coils, but I was rather confused by the photo in that thread; the M and F springs appeared to be very similar, differing only by a few coils.

But drevyek's own observations and fohat's photo (which shows a very clear difference in coil number compared to the other photo) does not help in clearing up my confusion. Does seem that in general, Model F springs should have at least a few more coils..

I figured if the springs were similar enough, it would be okay to replace Model F springs with those from an M, the latter being much easier to procure, if I ever needed to. In any case, I'll be disassembling an XT and an F122 soon so I guess I'll have a look for myself.

EDIT: Phrasing

[drevyek]

A visual inspection of M and F springs shows them to be pretty similar (XT vs '1401 from '92). Same length, same radius of coil, same number of turns. There may be material differences though.

Here is the photo that I took:

Just took another look at my F and M springs- your M springs are much shorter than mine. Although, the F spring does have more turns, looking closer.

Here's mine (bad lighting, sorry):

Spoiler:

[micrex22]

A visual inspection of M and F springs shows them to be pretty similar (XT vs '1401 from '92). Same length, same radius of coil, same number of turns. There may be material differences though.

Here is the photo that I took:

Just took another look at my F and M springs- your M springs are much shorter than mine. Although, the F spring does have more turns, looking closer.

Here's mine (bad lighting, sorry):

Spoiler:

Fohat's picture may just be due to the way they're positioned or something else, but the springs would have to be the same height as F and M share the same dimensions and all of my F and M springs are the same in height. I've compared all generations of Model M springs and they remain consistent with the amount of coils and length:

(left to right: early IBM, '90 Lexmark, '14 Unicomp)

From what I'm told, all variations of the Model F flippies are the same in height:


Proof my F flippies are the same height as the unicomp M flippies:


The Model M springs have less coils presumably due to the fact they need to be more stiff when pressing on the rubber mat and membrane.

[E TwentyNine]

Is this true? This GH thread says that if you switched springs on an Model F flipper, the difference in feel between Model M and F springs is not significant enough to be noticeable.

Model M springs have less coils and as a result are more stiff; that's a scientific fact. The more coils you have in a spring the easier it is to compress. The whole reason why Model Fs feel so different is the fact that the rubber mat is gone and the springs have more coils...

That GeekHack thread is sadly a heavy dose of misinformation.

The hell it is. Try it yourself. Randomly switch a few springs between an M and an F (or have someone do it for you so it's double-blind) then see if you can note which keys have the switched springs.

[y11971alex]

The rigidity of the materials and the diameter of the wire used in the springs also affects the properties of the resulting spring.

No need to get mad over scientific facts, when there are a million that could affect the spring.

[Chiovatto]

Can I ask something?? Whats the difference between Models M and F??

[y11971alex]

Can I ask something?? Whats the difference between Models M and F??

They are almost the same, except one uses membrane contact sensing and the other uses capacitive sensing. This leads to a slightly different touch.

The construction is, however, quite different. Model F are typically heavier and last longer due to capacitive sensing, rated to last over 100 million operations.

[fohat]

Can I ask something?? Whats the difference between Models M and F??

The internal construction is totally different and there are no interchangeable parts whatsoever except for the key caps.

The Model M was designed as a massive cost-reduction "replacement" for the Model F.