UK Vintage Radio Repair and Restoration Powered By Google Custom Search Vintage Radio and TV Service Data

Go Back   UK Vintage Radio Repair and Restoration Discussion Forum > Specific Vintage Equipment > Vintage Computers

Notices

Vintage Computers Any vintage computer systems, calculators, video games etc., but with an emphasis on 1980s and earlier equipment.

Closed Thread
 
Thread Tools
Old 9th Oct 2015, 10:36 am   #21
reggitsti
Retired Dormant Member
 
Join Date: Oct 2015
Location: Manchester, UK.
Posts: 4
Default Re: The Sinclair / Science of Cambridge MK14

Bit of a random one, but I stumbled across this thread whilst looking for a usable picture of a (ideally working) MK-14 for a book I've just finished on home computing in 1980s Britain. Don't suppose anyone out there would be able to will to take a photo or two of their MK-14 for me please?

Cheers,

Tom
reggitsti is offline  
Old 9th Oct 2015, 6:44 pm   #22
SiriusHardware
Dekatron
 
Join Date: Aug 2011
Location: Newcastle, Tyne and Wear, UK.
Posts: 11,471
Default Re: The Sinclair / Science of Cambridge MK14

Although working, mine isn't in original condition (it lacks the original keypad) so it wouldn't be the ideal 'model' for photographs for your book.

You need one which will look instantly familiar to anyone who ever owned one, ie, one with its original keypad. The reason so few survivors have original keypads is because the original pads didn't work very well and they tended to be replaced with something which worked better at the earliest opportunity.

When we were last actively discussing the MK14 here, Tony's MK14 was out of action because it needed a CPU, although I seem to remember that he had some other SC/MP based machines that he could pull a CPU from if need be. (...Tony?)

Failing that, I understand that the National Museum Of Computing has an absolutely pristine original example of an MK14, so maybe you could come to some sort of arrangement with them?
SiriusHardware is offline  
Old 9th Oct 2015, 7:49 pm   #23
TonyDuell
Dekatron
 
Join Date: Jun 2015
Location: Biggin Hill, London, UK.
Posts: 5,180
Default Re: The Sinclair / Science of Cambridge MK14

Yes, mine is currently missing the CPU. I have other SC/MP machines I could borrow a CPU from but for the purposes of a photograph I would guess any 40 pin DIL chip would do (it would be trivia to make sure the number wasn't readable in the photo ).

But the killer is that mine doesn't have the original keyboard either. I found the original keyboard to be totally unusable, so I soldered keyswtiches that Maplin sold at the time to the PCB. The PCB already had the traces and pads for them
TonyDuell is online now  
Old 10th Oct 2015, 11:04 am   #24
SiriusHardware
Dekatron
 
Join Date: Aug 2011
Location: Newcastle, Tyne and Wear, UK.
Posts: 11,471
Default Re: The Sinclair / Science of Cambridge MK14

Quote:
Originally Posted by TonyDuell View Post
I soldered keyswitches that Maplin sold at the time to the PCB. The PCB already had the traces and pads for them
At least that's an 'official' upgrade which was intentionally made possible by the design of your later PCB, but I agree that a machine with the original (awful) rubber mat keypad would be most truly representative of the type.

One with the official 'plastic dimple' button upgrade would be an acceptable compromise since it doesn't look too different to the original rubber mat type.
SiriusHardware is offline  
Old 12th Oct 2015, 9:59 am   #25
reggitsti
Retired Dormant Member
 
Join Date: Oct 2015
Location: Manchester, UK.
Posts: 4
Default Re: The Sinclair / Science of Cambridge MK14

Hmm, thanks that's interesting! I'm not too puritanical about it having the original membrane keypad actually. I'm more taking the view that the picture of an MK14 would be there to represent typical hobbyist computing in general, rather than the MK14 design per se, (to be honest I'd be happy with a NASCOM or System 1 instead, but MK14 seemed a bit more likely to find) and so if it's been modified a bit then that's quite in-line with the spirit of hobbyist computing anyway!
reggitsti is offline  
Old 13th Oct 2015, 6:35 pm   #26
SiriusHardware
Dekatron
 
Join Date: Aug 2011
Location: Newcastle, Tyne and Wear, UK.
Posts: 11,471
Default Re: The Sinclair / Science of Cambridge MK14

If you were devoting a whole page to pictures of the MK14 (unlikely) then yes, it would be interesting to see some customised ones alongside one really good image of an original one, but if it's only going to be one image then I honestly think it should show an MK14 as it was originally sold. (But it's your book, of course, so you ultimately get to say what can / should go in it!)

You haven't really said whether your book tends towards the nostalgic or the technical or the drily historic (perhaps all three) but the nostalgic buyer will be wanting to find images and information which spark off memories of something they used to have.
SiriusHardware is offline  
Old 17th Oct 2015, 5:13 pm   #27
Telleadict
Hexode
 
Join Date: Dec 2005
Location: Nr. York, North Yorkshire, UK.
Posts: 348
Default Re: The Sinclair / Science of Cambridge MK14

Hello

Tom: If you're still looking I've re-discovered my bookmark for the Planet Sinclair website which has a few pics of the Mk14. Maybe if you contacted the maintainer and explained what you are trying to do he might let you use one or two.

just a thought if you can't find anything better.

William
Telleadict is offline  
Old 19th Oct 2015, 3:54 pm   #28
reggitsti
Retired Dormant Member
 
Join Date: Oct 2015
Location: Manchester, UK.
Posts: 4
Default Re: The Sinclair / Science of Cambridge MK14

Thanks! Broadly speaking it's popular-social-history-of-technology with a bit of nostalgia thrown in. Specifically, I was hoping to include a picture of a hobbyist computer primarily to illustrate the transition between hobbyist computing (naked circuitry, expectation that user will tinker with it, slightly arcane I/O methods, kit built etc) and the more consumer oriented products that followed. Sadly I think the images on Planet Sinclair are too low in resolution for printing.
reggitsti is offline  
Old 19th Oct 2015, 7:28 pm   #29
SiriusHardware
Dekatron
 
Join Date: Aug 2011
Location: Newcastle, Tyne and Wear, UK.
Posts: 11,471
Default Re: The Sinclair / Science of Cambridge MK14

Reggitsti, good luck with the book. Sorry we can't seem to help you with a decent / appropriate image ourselves.

You could try to get in touch with the owner of this Youtube video -

https://www.youtube.com/watch?v=aGt9E46gH14

- this is the cleanest looking almost-original (and working) MK14 I have ever seen on Youtube. Its 'dimple button' keypad is one which was available as an option from Sinclair, so it qualifies as sufficiently original, and it looks very similar to an original MK14.

The quality of the video itself is also very good, so there is some hope that he might be able to provide you with images of sufficiently decent technical quality.
SiriusHardware is offline  
Old 19th Oct 2015, 8:23 pm   #30
reggitsti
Retired Dormant Member
 
Join Date: Oct 2015
Location: Manchester, UK.
Posts: 4
Default Re: The Sinclair / Science of Cambridge MK14

Sadly I did in fact try that already
reggitsti is offline  
Old 24th Jul 2016, 4:38 pm   #31
Mad Mal
Tetrode
 
Join Date: Jul 2016
Location: Spennymoor, County Durham, UK.
Posts: 69
Default Re: The Sinclair / Science of Cambridge MK14

Sinclair brought out the ZX80 after this. and many "home brewers" regularly expanded the pathetic amount of ram with do it yourself memory expansions. If the Mk 14 had just gone down that route a little further... but sadly it was not to be. But it did introduce many enthusiastic young things to the "joys" of Machine Code programming.
Mad Mal is offline  
Old 25th Jul 2016, 11:39 pm   #32
SiriusHardware
Dekatron
 
Join Date: Aug 2011
Location: Newcastle, Tyne and Wear, UK.
Posts: 11,471
Default Re: The Sinclair / Science of Cambridge MK14

..or 'The Joy Of Hex', as I like to call it...
SiriusHardware is offline  
Old 10th Oct 2016, 11:40 pm   #33
SiriusHardware
Dekatron
 
Join Date: Aug 2011
Location: Newcastle, Tyne and Wear, UK.
Posts: 11,471
Default Re: The Sinclair / Science of Cambridge MK14

I've just been looking around for anything 'new' in the MK14 world and I keep coming across old references to the gentleman who for a while was making modern 'Mark 2' reproduction versions of the MK14, as in here:-

http://mymk14.co.uk/

That website remains a good resource for MK14 related matters but it seems to be frozen in time and I don't think there's anyone on the end of the email on that page any more.

If it's the same person he was also going by the twitter handle of 'MK14man' but does not seem to have been active online for quite a while, as far as I can see.

Does anyone know if he is still around somewhere?
SiriusHardware is offline  
Old 11th Oct 2016, 8:30 pm   #34
Karen O
Rest in Peace
 
Join Date: Jul 2011
Location: Bridgnorth, Shropshire, UK.
Posts: 787
Default Re: The Sinclair / Science of Cambridge MK14

I exchanged emails with mk14man a while back when he was contemplating another replica build. I don't know how far that got. I get the feeling he's very busy workwise. One of the replicas he built was based on my PIC emulation of the Mk14.
Karen O is offline  
Old 11th Oct 2016, 9:38 pm   #35
SiriusHardware
Dekatron
 
Join Date: Aug 2011
Location: Newcastle, Tyne and Wear, UK.
Posts: 11,471
Default Re: The Sinclair / Science of Cambridge MK14

I communicated with him for a time via email as well around 2010-2011, but not since then. He just seems to have dropped off the internet with alarming suddenness, hence my query.

I really should build one of your PIC MK14s, assuming that the design was open-source of course. It would be nice to play about without putting too much wear and tear on the real thing.

Does it emulate the hardware input and output flags and RAM I/O device (INS8154) as well? Or is it limited to keypad input and display output?
SiriusHardware is offline  
Old 12th Oct 2016, 4:42 am   #36
Karen O
Rest in Peace
 
Join Date: Jul 2011
Location: Bridgnorth, Shropshire, UK.
Posts: 787
Default Re: The Sinclair / Science of Cambridge MK14

There's no RAMIO. It's a close emulation but there are differences: address arithmetic DOES carry over into the top 4 bits and the memory map is not absolutely identical. Also, my emulation runs at 4MHz - the Mk14 was fitted with a colour crystal. The flags, sense and serial IO pins are there if you use the right PIC (PIC16F877). The emulation is accurate for code running in RAM but runs slower for ROM. This might affect cassette routines in ROM, though serial download (intel Hex) is included and avoids the need for cassettes.

There's also a bug in the original source. SC/MP jumps do not partake of extension register offsets but that's not clear in the datasheet. This lead to the 'JMP 80' bug. It should jump -128 bytes but instead jumps by an offset derived from the EXT register. Amazingly, that went undetected for some while. I ran NIBL Basic successfully with that bug! It was only discovered when someone wanted to use an earlier version of the SCIOS monitor. I'll send corrected files if you ever make one of my emulators.

There's a bug also in the original code which stops flag IO from working. I've corrected that too.

I recently made another of my emulators (see photo). It's in honour of the Apollo guidance computer - the DSKY (display/keyboard). It includes flag IO on a 9 way 'D' connector.
Attached Thumbnails
Click image for larger version

Name:	DSKY PIC14.jpg
Views:	319
Size:	54.1 KB
ID:	131177  
Karen O is offline  
Old 12th Oct 2016, 6:57 pm   #37
SiriusHardware
Dekatron
 
Join Date: Aug 2011
Location: Newcastle, Tyne and Wear, UK.
Posts: 11,471
Default Re: The Sinclair / Science of Cambridge MK14

Super neat - how / where did you make, or get your keytops made?

For most of its life my MK14 lived in a very scaled - up plywood version of one of those 'star trek communicator' project boxes which were available from the likes of Maplin for a while. Imagine something that shape, but scaled up from a handheld to a 'desktop'.

In that configuration the MK14 mainboard was mounted inside the housing and the display and keypad were extended offboard to a calculator-style enclosure which sat on top of the plywood box. In recent years I have removed the 'lid' of the plywood box (effectively making it into a plywood tray) and returned the display and (non original) keypad to their proper places on the MK14 mainboard itself, but the keypad lettering looks as embarrassingly amateur as it always did, being done with Letraset transfers - which I found pretty difficult to lay down accurately on concave key tops.

In some ways the use of wonky Letraset lettering marks it as an unmistakable artefact of the seventies and it would almost be a pity to spoil that, but I would love to finish it off with properly printed or milled key tops, as I would have done at the time if I had had the resources to do it.

When I had a revival of interest in the MK14 around 2011, I started to try to write my own SC/MP assembler in Python so I became aware of the -80H = offset by the contents of the E register quirk. As it happened, I found someone who had already written an open source generic assembler in Python. Although it didn't include support for 8060/SCMP out of the box it was written so nicely that it was relatively straightforward to add 8060 to it.

I know people have used TASM over the years but I wanted something cross-platform so that I could easily run it on the Raspberry Pi (The idea of using a Pi to programme the original cheap, uncased British computer was just irresistible).

I already have a 40-pin DIP PIC18F877 in a very configurable'development' board made from veroboard with screw terminal connections for all the I/O ports. I take it the 40-pin DIP version is enough, you don't use the extra few pins available on the flat-pack version?
SiriusHardware is offline  
Old 12th Oct 2016, 8:19 pm   #38
Karen O
Rest in Peace
 
Join Date: Jul 2011
Location: Bridgnorth, Shropshire, UK.
Posts: 787
Default Re: The Sinclair / Science of Cambridge MK14

The 'keys' are an illusion. It is a laminated print-out with click switches behind it. You have to hit the keys fairly squarely or the stroke doesn't register. One day I might fit it with real keys (once I work out how!)

Yes, the 40 pin DIL package is fine.

My original design used transistors for column drive, which ordinarily wouldn't be a problem but some of the example programs don't bother with a blank period between digits, and this causes ghosting because the transistors don't switch off quickly enough. It's my own fault for assuming everyone else would take the same care that I would when driving a multiplexed display. The problem is solved by replacing the transistors with a 74AC244. I added 'speed up' capacitors to my prototype.

My Mk14 also went through case incarnations. First it was a huge slab of chip board with a way over size fan and contiboard case. Then it went into a much smaller metal case with an external display/keypad in a plastic flip case (like the Star Trek communicator but only about 10" long).

Last edited by Karen O; 12th Oct 2016 at 8:23 pm. Reason: Mention various cases my Mk14 had
Karen O is offline  
Old 12th Oct 2016, 8:56 pm   #39
SiriusHardware
Dekatron
 
Join Date: Aug 2011
Location: Newcastle, Tyne and Wear, UK.
Posts: 11,471
Default Re: The Sinclair / Science of Cambridge MK14

In its earliest cased incarnation my MK14 was installed in a hard briefcase with the main board mounted in the lower half, a white opaque perspex panel mounted neatly over the top of it and the display and keypad extended into a Texet 880 calculator body mounted on that.

It looked great, as far as I remember. No idea why I didn't keep it that way. Maybe the PCB wasn't accessable enough. Or maybe it ran too hot, as there was little or no ventilation. Fully expanded with the extra RAM and RAMIO, it draws roughly half an amp at 5V. Nearly half of that is drawn by the two bipolar PROMs which hold the monitor code.

You used the same keypad / keyboard solution on your PIC based Basic computer, I remember now.

The very low profile switches I used (a long time ago now) for my MK14's current keypad are C&K 'MDPS LFS' series - that's just the switch. The keytops (plain) have their own part numbers, for example, red keytops are "BTN MDP 40", blue ones are "BTN MDP 60". The grey ones are "BTN MDP 20". Last time I looked it was still possible to obtain them from Digikey.

An alternative would be another C&K series, the KS11R.. series. The latter have integral coloured keytops so you would need to buy them in the required quantity of each colour. Both types insert into 0.1" matrix board such as veroboard and are designed to be used in a close fitting row / column layout with only very small gaps between the keys.

Do you have an up to date link for diagrams and either source (presumably MPLAB assembler) or assembled program code for the PIC-MK14 project?

Last edited by SiriusHardware; 12th Oct 2016 at 9:10 pm.
SiriusHardware is offline  
Old 17th Oct 2016, 1:29 pm   #40
Karen O
Rest in Peace
 
Join Date: Jul 2011
Location: Bridgnorth, Shropshire, UK.
Posts: 787
Default Re: The Sinclair / Science of Cambridge MK14

I'll be happy to make the code for my Mk14 available. I'm a bit busy at the moment: I'm preparing for a gathering of the NBTVA at the of this week but I'll get a round tuit after that.
Karen O is offline  
Closed Thread

Thread Tools



All times are GMT +1. The time now is 6:09 am.


All information and advice on this forum is subject to the WARNING AND DISCLAIMER located at https://www.vintage-radio.net/rules.html.
Failure to heed this warning may result in death or serious injury to yourself and/or others.


Powered by vBulletin®
Copyright ©2000 - 2024, vBulletin Solutions, Inc.
Copyright ©2002 - 2023, Paul Stenning.