Re: MK14 schematic revisions
 

Hope it's OK to post this here, but I've just noticed that the JM precision replica MK14 PCBs are, at the time of the writing this (April 2020), somewhat reduced from their original price.

http://jmprecision.co.uk/shopping/pg...hp?id=136&=SID

Everyone who has one of these (including several people here) says they are very nice PCBs.

Re: MK14 schematic revisions
 

Hmm still pretty pricey but I guess its a tried and tested design.

Re: MK14 schematic revisions
 

I did think the original price was quite high for a bare PCB, that was just my personal view and quite a few people obviously disagreed, bought them at the original price and were very happy with them.

There is no doubt that they are beautiful looking PCBs and I have admired the accessories, especially the keypad, which are offered as optional extras for the JM PCBs. It's a very nice, finished product. I get the impression there are a limited number remaining, so there may not be any more forthcoming after the current batch have gone.

For 'hardcore' enthusiasts the Czech 'Martin' PCB with its neutral (not green) colour and specially manufactured adhesive keypad overlay looks more authentically retro and, like yours, has the unwanted PROM images removed making it much easier to map more RAM into that area. It also has contact fingers on the underside of the rear edge connector, as per original issue IV / V PCBs, which make it a little easier to add external extras like the VDU - although it is still necessary to route those connections to the buses yourself.

Tim and I still intend to order a batch of your advanced 'issue VI' PCBs - I have collected almost all needed parts now, bar the RAM and key switches. Unfortunately - as at times in the past - real life is getting in the way of things just at the moment.

Re: MK14 schematic revisions
 

hello to all
I hope everything is right for you
I took over my project after ordering the pcb a martin (very nice and super diy)
I gently found the necessary elements now I attacked the assembly phase;D;D:thumbsup:

Re: MK14 schematic revisions
 

Of all the replicas, the 'Martin' PCBs look the most historic, especially the keypad which is very close to original.

We think they are an exact copy of the original 'Issue V', which was the final version.

I am collecting parts for a replica too. Just now my RAM is somewhere between America and England. I do not know if it will arrive here!

Re: MK14 schematic revisions
 

Take care sticking down the keyboard components - Martin's instructions on the web are a bit strange, probably the translation, but the clear sticky sheet with the larger holes goes down first then the metal domes and then the clear sheet with the smaller holes, which holds the metal domes in place.

Make sure all the plastic bits are removed from the holes - they are a real pain to remove after it is stuck down,

Test the switches before sticking down the top sheet with the key legends on.

http://www.8bity.cz/replika-mk14/parts-for-mk14-build/ Keyboard section.

Good luck with your build
Cheers :beer: David

Re: MK14 schematic revisions
 

and yes we live a funny situation
I print in 3d some visiere also and I resume this project only missing the tablecloth
I read the whole forum on mk14
the martin keyboard is a
address and care patience test
but it works (ohmtre test)
read the tips of martin
to centre the sheet I made guide in 3d

Re: MK14 schematic revisions
 

On original MK14s the key overlay sheet was mainly white, with the key legends on it in black. The broad black outline seen on the first picture in the previous post was originally another layer, a frame made from metal (anodised aluminium, I think) and it was held down by four plastic 'rivets' similar to those made by philoupat83.

These are almost exactly like the white ones supplied with the original kit, although the dimensions may not be exact (I have not checked the diameter of the holes in the PCB so do not take my word for it that they will fit. There are many others in this range).

https://cpc.farnell.com/essentra-com...ite/dp/FN04481

Re: MK14 schematic revisions
 

I made them randomly in mm and not inch
excuse my !:shrug:

Re: MK14 schematic revisions
 

I have the martin sticker but I will make a black 3d cache like jpm

Re: MK14 schematic revisions
 

hi all finished editing my MK14 keyboard in 3d printing everything works with XOR the keyboard and not top I prefer my PIC14 for programming

Re: MK14 schematic revisions
 

Excellent implementation of the keypad frame and buttons!

How do they feel when you press?

PIC14 is good to develop MK14 code on because it has serial code download included.

Re: MK14 schematic revisions
 

thanks
I think that still needs to change the shape of the keys still not cool bounces
yes I like the port serie a programming in assembler compilation pouring and voila
a great thing for education thank you karen

Re: MK14 schematic revisions
 

I palm my 3d keyboard and I would like to add a connector for a future VDU which connector?

Re: MK14 schematic revisions
 

The original VDU is made to use a DIN card rack connector.

See post #133 of this thread for images of a VDU PCB fitted with that type of connector.

There are also further discussions in this thread, post #167 onwards regarding the best way to connect the VDU to the MK14 rear connector.

Your Martin replica probably has contacts on the lower side of the rear edge connector. You can wire the required system Address, data and control signals to these so they are available for the VDU.

Your JM replica PCB probably does not have contacts on the lower side of the rear edge connector.

Therefore, the 'Martin' PCB is the best one to use with a VDU if you have both versions.

Re: MK14 schematic revisions
 

thanks

Re: MK14 schematic revisions
 

I've been involved in a conversation in another forum with someone who had a newly built 'Martin' replica which wasn't really resetting properly with the reset switch, although he discovered that if he disconnected the reset capacitor, the board would reset properly with the switch. But then it did not reset properly at power on.

The fix he arrived at was to put a 0.1uF across the reset -resistor-, and now his Martin replica resets properly on power up and resets properly with the reset switch. I seem to remember Tim and Slothie both had problems with 'dirty' reset on their JM PCBs, so it would be interesting to know if this is also a 'fix' for the JM PCB.

There's an added complication, in so far as the JM PCB probably uses the original 'reset switch down to 0V, two gates' scheme whereas the Martin PCB has one less gate and the reset switch going up to positive.

Do the Martin and JM PCBs have plenty of decoupling capacitors on the 5V supply, or are they both similar to the original MK14 with almost none?

Re: MK14 schematic revisions
 

As with the original they have little or no decoupling - in that sense the JMP ones are exact replicas of the VI/II boards. As you say they have the traditional pull down circuit as well. My reset is pretty reliable. The reset issues we had were with the PI programming board and its timing of a reset rather than the board itself - but, I suppose if the CAP charges too soon it will being the power up from the zero level which was what was happening for me.

Attachment 204890

Re: MK14 schematic revisions
 

Yes, I certainly do remember you having to twiddle with the reset timing on the uploader and come to think of it the machine Slothie had reset problems with was actually his own original replica.

I don't know whether he ever sorted that.

Re: MK14 schematic revisions
 

I worked out by experiment that discharging the power supply electrolytic made it reset properly on power up. I thought the problem might be power supply noise as there was a lot, adding a few decoupling capacitors seems to have fixed the problem.

Re: MK14 schematic revisions
 

Hello
on my retraction martin no problem of reset my supplies with a stabilized power supply without decoupling to the old so no harmonic in the regulator and the filter capacitor or that of the reset

Re: MK14 schematic revisions
 

My parts collection for my 'Slothie' replica MK14 is one step closer to completion, as the RAM is not far away now. Unfortunately I have had to pay Royal Mail £6 + £8, some of that Customs duty (not unexpected) and some of it 'Handling Charges' (??) in order to get it delivered. That has added quite a bit to the otherwise modest cost of the parts.

Now only requires key switches ... and a PCB to build it on.

Re: MK14 schematic revisions
 

It's a shame because that handling charge is for collecting the duty! I think my RAMs came duty prepaid which means you save the handling charge, but the postal charges were suspiciously high.

Re: MK14 schematic revisions
 

I just thought i'd give this a tentative nudge by uploading the .zip file you (Slothie) posted to this thread a while ago to JLCPCB, the PCB manufacturing outfit I think you said you have used before, just to see what the cost is at the moment.

https://jlcpcb.com/

When I hit 'Add Your Gerber' and upload the .zip file it seems to swallow it OK and fills in a lot of details for me, but when I go 'Add To Cart' it flags up the fact that I have not filled in the dimensions. I find this confusing, as I would have thought the dimensions were embedded in the design.

Do you remember having to supply the dimensions separately?

Re: MK14 schematic revisions
 

No, one of the reasons I chose JLCPCB rather than PCBWAY was it got all the info from the zip file. Strange.

Re: MK14 schematic revisions
 

The dimensions are on one of the drawing layers.

Re: MK14 schematic revisions
 

I've just tried again but using the file you attached to your original post about this in the 'vdu' thread - that one uploads OK, and including with dimensions.

Appx cost at present is about £12(!) for 5 PCBs and about the same again for postage.

Re: MK14 schematic revisions
 

That's cheap! Does the preview look the same as it does in kicad? I uploaded the file to bitbucket and the forum from the same file.... Strange!

Re: MK14 schematic revisions
 

Yes, broadly, I mean all its arms and legs are attached. It looks OK in the JLCPCB preview.

I didn't go further yet because I would have had to create a sign-in / profile. I'll do that when I am feeling a bit more alert.

Re: MK14 schematic revisions
 

This is sounding promising...

Re: MK14 schematic revisions
 

hello
to timbucus which display you used your replica is superb:thumbsup:

Re: MK14 schematic revisions
 

yes JLPCB is not expensive I intend to make them the pcb of PIC14 v2 of KAREN

Re: MK14 schematic revisions
 

I think that large display is one of the optional extras offered by JMP in the UK.

I will look into ordering a batch of PCBs later today, as long as the process (especially payment) seems safe. It helps that I know Slothie has already used them without any apparent issue.

Re: MK14 schematic revisions
 

I don't know if you mean to make your design public domain or to sell them, but I am sure Karen would probably appreciate one if you have any left over.

Re: MK14 schematic revisions
 

It was actually sold by a trader on e-bay called trev_ham https://www.ebay.co.uk/usr/trev-ham who offered after market parts for the JMP board (Display filter for traditional displays, the large display, Physical Key tops which I did mean to buy) and also the Acorn System 1 board. He does not seem to have a presence at the moment but, if you want one I am sure if you contact through the above link him he might be able to help.

Re: MK14 schematic revisions
 

Well I just spent several hours trying to get the zip files uploaded to JLCPCB and finally worked out the correct incantation to get my phone to select the zip files!
The result from this effort is that both the file downloaded from the forum and from Bitbucket produce the right PCB in the preview and pick up the board dimensions correctly from the zip file. So I'm a little puzzled. I used Chrome browser - what browser did you use?

Re: MK14 schematic revisions
 

Chrome. (On a desktop PC - I don't use a phone to access the 'net unless I am absolutely desperate).

The first one I tried to upload was one that I saved locally to HDD because I wasn't sure how long you intended to leave it up on bitbucket, or whether that source would just automatically time out. Despite having the same date and same file size the JLCPCB website did not fully accept that saved version.

The second one I uploaded was the one you posted in the VDU thread, saved to my HDD and then immediately uploaded to the site. That worked fully, supplying the dimensions as well.

It might be that the first version was perfectly OK as well and something just went a little bit wrong at the first upload attempt. Maybe if I had attempted to upload it again it would have gone in properly. Not having done it before, I didn't know whether it was normal to be expected to define the dimensions separately. (Which is why I came and asked).

Re: MK14 schematic revisions
 

Well I am desperate because I haven't had my hands on a proper PC in eight months :) At least now I know the files do still work and it seems JLCPCB have got a bit cheaper!
For my first order I got free shipping so once you've created your profile, if they're doing that the PCB's will be really cheap for you!

Re: MK14 schematic revisions
 

Looking back through this now ancient thread - it is probably mentioned in the Domesday book somewhere - I notice your original 5 PCBs cost you £18 including free shipping. I have no idea that will also be applied to me, we'll just have to see.

Re: MK14 schematic revisions
 

Hello to all
yes the pcb will be public i ordered 5 on jlpcb (very well no problem of payment paypal control of the pcb etc) as I would have tested it I could put the file on site or sent what I will have left to you

Re: MK14 schematic revisions
 

Thanks for that assurance regarding JLCPCB.

I was thinking mainly that Karen could have one of your PIC14 V2 PCBs, it is probably the least anyone can do after the work she put in creating the PIC14 project.

Re: MK14 schematic revisions
 

It would be great if you put the design files and or gerber files on the forum (perhaps on its own thread?) Because a number of people including myself would like to build one sometime.

Re: MK14 schematic revisions
 

I will create a thread for the design of this wonderful processor learning tool :thumbsup:

Re: MK14 schematic revisions
 

It's done, I have ordered a batch of 5 'MK14 issue VI" PCBs - I didn't get free 'new guy' discount or carriage, possibly because the site recognised that these PCBs have been submitted to it before.

The site initially added the price for fastest possible carriage which gave me a bit of a heart attack - cost was about three times the cost of the PCBs, but then I backed it down to the slowest, most basic option and it settled down to a more soothing ~£25 for the PCBs + carriage. I may still be hit with duty on top of that, of course.

So now I'm in a race against Slothie to be the first to build one of his issue VI PCBs!

Re: MK14 schematic revisions
 

Well my money's on you winning. It could be many months before I get access to my tools and parts!

Re: MK14 schematic revisions
 

Tim will get one as soon as I have them, so we may end up in a three-way race.

Now, we just have to wait.

Re: MK14 schematic revisions
 

Better finish some of my other projects then - looking forward to this as I have held off doing my VDU until I had a better connection for it as well.

Re: MK14 schematic revisions
 

MY RAMs finally made it here. I sincerely hope they were worth all the trouble and expense.

Unfortunately the RAM in my real MK14 is not socketed so I can't just put them in that and test them. My device programmer has a chip test mode which can check most 74xx series logic, most 4xxx series logic and quite a few RAMs including 2114s, but not 2111s.

I'm considering making an adaptor to make a 2111 'look' like a 2114. It depends what the test does - if just writes a value to address aaaa and reads it straight back from address aaaa then moves onto the next address, then I could probably rig an adaptor which would make it run through a 2111 four times, all the while thinking it is testing a 2114 once.

Re: MK14 schematic revisions
 

a 2114 ram tester that I have already used can be modified for 2111
https://github.com/Danjovic/2114-Tester

Re: MK14 schematic revisions
 

I love it when this happens. :thumbsup:

I have already 'installed' it, I will modify it for 2111. First I will make myself an 18-pin socket to Arduino adaptor so that the connections will be reliable.