MK14 schematic revisions

[Slothie]

Mine just has 4 flying wires that go to the other PROM (top right on board) and plugs into the LHS (high nibble) socket.

[Slothie]

Originally Posted by Mark1960

I found the 12x12 tactile switches with white caps and clear covers on amazon and nearly missed that you used a different reset switch but found a set of twenty on ebay that look similar to the switches on my MK14 IV.

Yes, I originally did that because that's what the original had. If I do an updated board I'll consider putting in a dual footprint for either type of switch in all locations. The switches are the "D6" style originally made (I think) by CK, but copied by others. They still seem to be available. You used to be able to get caps for the square variant, although I've not seen them latterly - they probably wouldn't be hard to make on a 3D printer though I imagine.

[Mark1960]

Originally Posted by Slothie

Mine just has 4 flying wires that go to the other PROM (top right on board) and plugs into the LHS (high nibble) socket.

I like that idea better, saves an extra 100mA on the power supply.

[Buzby123]

Originally Posted by Slothie

... If I do an updated board ...

Hi Slothie,

If you do an updated board, can you please flatten those 4 'stand up' resistors ?. They seem to be always getting knocked over.

Apart from that, I like your board !.

Cheers,

Buzby

[SiriusHardware]

Originally Posted by Buzby123

If you do an updated board, can you please flatten those 4 'stand up' resistors ?.

I think they were part of Ian's attempt to get the PCB to look recognisably like the original - it's amazing how close he got, considering he never at any point had an original PCB to make measurements from.

You could probably replace those resistors even on the current issue VI with SM resistors of appropriate length soldered between the pads either on the top side or the underside of the PCB.

They could also be replaced with a 4-resistor SIL package if a through-hole was made available for the fifth (common) pin.

[Buzby123]

The 'stand up' resistors on Micky are still intact after 40 years, but the ones on Vicky are forever getting knocked over.

A close inspection reveals that 40 years ago I put the body of the resistors hard down to the board. Obviously I paid no heed to overheating the things, now I always leave a bit of wire on show.

Ian's effort in re-creating an 'as near as perfect' reproduction of the MK14 is to be commended. I am looking forward to getting my Vicky going, and it would never have been possible without VI.

[SiriusHardware]

As a point of interest those upright resistors are 1/8th watt resistors on my original MK14, those were the resistors SOC supplied, no doubt with the intention of giving them a lower vertical profile. They don't handle any significant current so there would be no problem mounting them with one end the body right down against the PCB.

[Slothie]

I did them like that because thats the way SoC did it, as Sirius said. I can't really see why, it wouldn't have been hard to find somewhere for 4 resistors horizontally. I imagine they may have been a late addition to the circuit and given the original PCBs were probably hand-taped moving stuff around wasn't an option. Much easier these days with CAD tools!

However having a quick look, the size 1/8w resistors are today, they would fit in the space horizontally!

[Slothie]

New replica on eBay looks pretty authentic, not mine btw! Ive snagged the photos for reference,

[Buzby123]

Originally Posted by Slothie

New replica on eBay looks pretty authentic ...

Yeah, where did he get that Old Skool PCB material from ?

[Timbucus]

Originally Posted by Buzby123

Yeah, where did he get that Old Skool PCB material from ?

That is a Martin Lukasec one - he has them made and they do look very authentic.

https://www.8bity.cz/replika-mk14/mk...ond-prototype/

Click on the English Flag for a translation.

[SiriusHardware]

How many replicas are there now? Martin L's, The JMP replica, Slothie's issue VI, MK14man's modern tech replica from a few years back and and now also the ones which ortek_service's friend has produced - we don't really have a name for that one yet.

That's not counting known one-off replicas like this one:-

https://www.youtube.com/watch?v=vhSAMRwGL-A

[SiriusHardware]

Originally Posted by Timbucus

That is a Martin Lukasec one - he has them made and they do look very authentic.

Tim neglecting to mention there that he actually has one of those boards (albeit unbuilt). I keep pleading with him to scan it while it is still a bare PCB, as there's no telling how long Martin L will choose to keep making them for.

They are very close copies of the original SOC issue V, so it's essential that the PCB layout is widely preserved. I think the only difference is that the original PCB was laid out for 3-point switch domes and Martin laid his keypad traces out for 4-point domes, which was all he could get at the time.

[Timbucus]

Originally Posted by SiriusHardware

Tim neglecting to mention there that he actually has one of those boards (albeit unbuilt). I keep pleading with him to scan it while it is still a bare PCB, as there's no telling how long Martin L will choose to keep making them for.

They are very close copies of the original SOC issue V, so it's essential that the PCB layout is widely preserved. I think the only difference is that the original PCB was laid out for 3-point switch domes and Martin laid his keypad traces out for 4-point domes, which was all he could get at the time.

He is correct I do have one. He keeps pleading with me to build it as well as I am one of those weird people who likes having an un-built kit around as well...

Next time I have the scanner out I will do as asked.

[SiriusHardware]

..and don't forget to lay a rule alongside the edge of the PCB when you scan it (both sides) - it's the easiest way for people to check that the image on their screen really is actual size when they are trying to make measurements from it.

[Slothie]

Thanks to Tim for his post https://www.vintage-radio.net/forum/...&postcount=134 that has a link to the corrected MK14 manual with the missing page 88 restored. This is the last part of the moon landing program, but more importantly the first part of the "Duck Shoot" program that I wasted an unfeasible amount of time on as a teenager with my teachers MK14!

I'd second the vote for the use of a ruler of some kind on any scans of the PCB!

[SiriusHardware]

I always used to change the character definition for the 'Duck' because I didn't think the default character looked enough like a duck. I must have been a lonely child...

[Mark1960]

Originally Posted by Timbucus

He is correct I do have one. He keeps pleading with me to build it as well as I am one of those weird people who likes having an un-built kit around as well...

Next time I have the scanner out I will do as asked.

Should you not be asking permission from Martin before publishing his design in a form that would aid someone to make their own copies?

[SiriusHardware]

I'm seeking to preserve it, not to reproduce it, and only because it is the closest 'living' thing that there is to the actual layout of the original issue V - except for the odd unbuilt ACTUAL issue V PCB which may still be out there in the wild somewhere.

It would, admittedly, assist with things like reproducing the correct key spacing on a future revision of the issue VI but that would not be a wholesale copy.

[Slothie]

Originally Posted by Mark1960

Should you not be asking permission from Martin before publishing his design in a form that would aid someone to make their own copies?

It is a bit of a tricky one, ideally I would prefer scans of an original board, but Martins is the closest to the original we have to hand. I'd not want to steal the work that Martin has done in improving the layout, the details that are interesting to me are not the details that Martin has added, but those that he has copied directly from the original. If we could secure permission it would certainly make me feel more comfortable. Even better, if he is no longer interested in selling the boards, maybe he could be encouraged to release his design files....

I already have photos of both sides of an original PCB, but they are from an eBay listing, and have no size reference, are of an issue IV (I'd prefer an issue V), are not particularly well focused, and are distorted because they are not photographed from directly overhead. I'd like to make a PCB design of the original (including the original contact arrangements) even if its just a retouched photo to the exact scale so that exact measurements could be made, and to actually document the original. Its not about making copies of Martin's work, it just acknowledges that he seems to have come closest to producing a clone of the original PCB. As far as making a clone of the MK14 I'm happy with my "interpretation" that physically resembles the original but is routed differently, but I'd still like to be able to have a precise diagram of the original PCB layout for posterity if its at all possible, and a scan of Martins board would be a valuable reference towards making that. If Tim just scans the PCB and hangs onto it himself before assembling it that would be something, in case permission was to arrive in the future.

I have made some attempt to "enhance" the images I have of an original board, and to remove the distortions, but with the poor quality of the image and having to estimate dimensions using the IC pins as a "ruler" I have had limited success and I need to spend some time writing a program to remove the dimensional distortion from the image - its kind of towards the bottom of my "to-do" list.

Of course, if someone has an issue V and doesn't mind disassembling it and scanning the PCBs...