MK14 schematic revisions

[Slothie]

Oh and the overall height/width and hole diameter for completeness. (G,H,I ?!)

[SiriusHardware]

When I dug out my INS8154 datasheet last night I found inside it the original MK14 pull-out component layout diagram which I think is actual size, so it shows not only the original positions of all the ICs but the keys as well. I'll see if I can scan it over the next few days, it may provide useful backup corroboration of the dimensions, along with the dimensions from Tony's original metal keypad frame.

Also - not sure if I read it correctly but I think Phil was offering to send one of his 3D printed frames across - I think he is going to be sending one or more of his Scrumpi 1 PCBs to Tim at some point in the near future.

[TonyDuell]

I have found my original SoC metal keypad frame now. Would you like me to make the same measurements. I don't think I can get a micrometer in there (and anyway I don't have one large enough to do the entire frame), I assume a vernier caliper will be accurate enough.

I am not convinced it's anodised aluminium though. It feels too heavy for that. I will test with a magnet just to be sure.

[Slothie]

Yes, it would be great to have those measurements on here for posterity. I'd like to get my board right dimension wise particularly around the keyboard given the accessories that are becoming available.

[SiriusHardware]

I have not seem my original key frame for decades, so my 'memory' of it being aluminium is probably wrong. I'm sorry to say I am sure that I threw away most of the original keypad components shortly after I built the replacement keypad the machine has now, thinking "Well, I won't be needing those again".

To understand that mode of thought you would really have to have experienced the full horror of the original issue II keypad. There was no thought of ever going back.

Oddly though, I do still have the original large conductive rubber square which was the 'active' part of the keypad. Maybe I thought it would come in handy for something else.

I'm wondering if the most useful thing Tony could do would be just to photocopy the frame several times and send the copies to Slothie, at some time when Slothie is in a better position to be able to use such materials.

[Slothie]

Were the letters and numbers printed directly onto the rubber sheet or were they on a different layer of their own? I remember seeing a diagram somewhere of the original assembly but can't recall exactly where. Also, did the keypad with dome switches have the rubber over the domes or something else? I have a vague memory of clear plastic buttons but that would require a frame to retain them so that must have been very different.

[SiriusHardware]

Also thanks to Phil for his beautiful scan of the 'Martin' keypad overlay - I still don't have the keyswitches for my issue VI but I have been pondering on the best way to produce the key legends to put under the transparent key caps when I eventually have them.

I did consider the 'Ransom Note' method of randomly cutting out the required figures from magazine pages, but it might have taken a few months to collect the command key words.

As it is, I can just scale that scan up or down, print it on white card and cut out the key legends all beautifully done in the original font.

Slothie, the key legends were printed in black on a sheet of their own. The versions with dome switches omitted the rubber sheet. There may have been an early dome switch version where the user pressed the domes through the key overlay sheet (as per Martin's current version) but the final SOC version used the same black metal frame to retain clear plastic buttons which pressed on the key overlay, which in turn pressed on the dome switches. All versions had a metal frame, but in the early versions the frame was just there to hold the key overlay in place on the PCB - it wasn't self-adhesive like Martin's is.

[philoupat83]

see sticker of martin mk14

[Timbucus]

I am seriously thinking (when I get my 3D printer fixed) of making a housing a bit like the one for the JMP I have to fit the Slothie 1.2 size holes and keys with a version of that printed to fit under.

The feel on the JMP keyboard is quite good and it makes it look close the original. The Green key caps will eventually annoy me - I am looking for white ones at the moment!

[SiriusHardware]

Thanks again Phil - that 'Martin' overlay actually represents two elements of the original keypad assembly. The key legends, 'Science of Cambridge' and 'MK14' were printed in black on a sheet of slippery, hard-wearing white plastic.

The heavy black outline framing the keys was not actually on the keypad overly sheet originally, it was an actual black metal frame laid over the top of the keypad overlay to hold it down flat on the PCB. That is the frame which Tony is talking about taking measurements from, and which Phil has 3D-printed a copy of.

[philoupat83]

see stl of 3d printer

[Timbucus]

Originally Posted by SiriusHardware

Thanks again Phil - that 'Martin' overlay actually represents two elements of the original keypad assembly. The key legends, 'Science of Cambridge' and 'MK14' were printed in black on a sheet of slippery, hard-wearing white plastic.

The heavy black outline framing the keys was not actually on the keypad overly sheet originally, it was an actual black metal frame laid over the top of the keypad overlay to hold it down flat on the PCB. That is the frame which Tony is talking about taking measurements from, and which Phil has 3D-printed a copy of.

If you take a look at the photo of Mr Staff's one on the cz forum you can see he had some anodized metal ones made - there is a picture of the stack of them some way further back in the thread.

https://translate.google.co.uk/trans...78640%23p78640

[Timbucus]

Originally Posted by philoupat83

see stl of 3d printer

Wow thanks - I really need to get my 3D printer working now.

[Timbucus]

I am also kicking myself I missed getting a set of these that trev_ham listed on ebay... he did them for a while for the JMP and Martin boards

I have said elsewhere perhaps if contacted as a seller he might do them to order if people were interested.

[philoupat83]

I also think mine need a great revision I made a hundred visiere for all my surroundings I am no longer of wire

[philoupat83]

a yes very interesting

[SiriusHardware]

Unfortunately I'm out, as even my original issue II MK14 would not accept those switches. If there is ever a rev 1.3 issue VI with the key positions remapped and re-pinned for those types of switches I would certainly go for it.

[Timbucus]

Originally Posted by philoupat83

I also think mine need a great revision I made a hundred visiere for all my surroundings I am no longer of wire

Well done you for doing that - I was planning to try to help with something like that but, I have failed to get the Z axis to work reliably - its a mechanical issue I have just not spent enough time (and probably money) on.

[Slothie]

Those look like standard D6 switches with custom keycaps. Later models of MK14 had provision for D6 switches didn't they?

[Timbucus]

Originally Posted by SiriusHardware

Unfortunately I'm out, as even my original issue II MK14 would not accept those switches. If there is ever a rev 1.3 issue VI with the key positions remapped and re-pinned for those types of switches I would certainly go for it.

Understood - it is not such an issue for me as I have the JMP version which works OK although it does not have the cutouts with the SOC and MK14 text on (I have a hand printed DYMO label on mine - very contemporary.

Now with Phil's STL once my printer is working I can add that to my Martin board to recreate the original feel to some extent - although a cold metal one is probably really needed.

If I get the printer working I will make an overlay for our VI boards in the fashion of the JMP one (I need a simple project for 3D design to learn) - if Phil doesn't buy more filament and do it first when he gets his Slothie VI...