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

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Old 14th May 2020, 11:14 am   #401
SiriusHardware
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Default Re: MK14 schematic revisions

I've modified the 2114 sketch to test 2111s instead, I just need to test the tester, as it were. The original sketch was nicely written and easy to read but I am bound to have made a mistake somewhere.

I've also just been notified that the issue VI PCBs have just gone in the post to me!
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Old 14th May 2020, 11:57 am   #402
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Default Re: MK14 schematic revisions

JLCPCB are pretty quick, I think mine arrived 7 or 8 days after I emailed the gerbers!
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Old 17th May 2020, 5:55 pm   #403
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Default Re: MK14 schematic revisions

PCBs are still enroute, but here is another little tessera for the MK14 mosaic, a 2111 SRAM tester sketch for the Arduino UNO. Connections between the UNO and the 2111 are explained in the comment at the start of the sketch.

This was unskillfully adapted from the original 2114 tester sketch written by 'Danjovic', which was found by Philoupat83 here:-

https://github.com/Danjovic/2114-Tester

Output is viewed on the serial monitor in the Arduino IDE @9600bd. The tests are quite basic and may not catch every possible fault on a 2111 but it will catch most. It passes one of my recently acquired AM9111s and of course announces a failure if I remove the chip.

It directly manipulates the port pins of the Atmega328 in order to run the tests at a high speed, so it probably won't run on any other Arduino board.

The Arduino file extension .ino is not a supported attachment here so I have wrapped it up in a .zip file.
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Old 21st May 2020, 10:15 pm   #404
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Default Re: MK14 schematic revisions

Still no sign of the new PCBs - where Slothie's own PCBs must have come on the stage coach, mine appear to be coming by slowcoach. To be fair, the situation is anything but normal at the moment. I'll be happy if they arrive at all.

One thing I'm still on the hunt for is suitable 16-way single sided edge connectors for the keypad edge connector and double sided 32-way edge connectors for the rear edge from which it will soon be possible to pick up all the useful signals - RS used to do two nice (but expensive) Cinch edge connectors which were exactly the right size but they have now discontinued them.

Anyone know where to find current supplies:-
Single sided 16-way, 0.1" / 2.54mm pitch, open ended, no key?
Double sided 32-way 0.1" / 2.54mm pitch, open ended, no key?
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Old 21st May 2020, 10:37 pm   #405
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Default Re: MK14 schematic revisions

I found a 50x2 0.1" connector on eBay and cut it at position 33 to give a 32x2 and 17x2 parts, and dremmelled off the extra contact to make it 16 way. I've not since found the connectors on eBay sadly.
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Old 21st May 2020, 10:49 pm   #406
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Default Re: MK14 schematic revisions

Yes I did the same but, the supplier is now not listing them.
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Old 21st May 2020, 10:51 pm   #407
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Default Re: MK14 schematic revisions

I intend to fit a DIN connector on mine so it just connects to the VDU so no need for the 32 way one.
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Old 21st May 2020, 11:00 pm   #408
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Default Re: MK14 schematic revisions

The other option is to adapt one of these https://www.ebay.co.uk/itm/Sinclair-...-/260906239646
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Old 21st May 2020, 11:07 pm   #409
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Default Re: MK14 schematic revisions

Quote:
I intend to fit a DIN connector on mine so it just connects to the VDU so no need for the 32 way one.
The reason I won't do that is because my VDU is an original, so I don't want to make even the very small modifications required to get everything to connect up (e.g, clock signal, which has had to be placed on the 'wrong' side of the edge connector).

I'll therefore use a short edge connector to DIN connector cable or stripboard assembly with the vast majority of the connections going straight through, thanks to the meticulous way in which Slothie positioned the connections on the issue VI, but with the one or two anomalies sorted out on the way across, rather than on the VDU.

I fully understand why you two would just do it with a 'hard' connection, kind of wish I could do it that way myself.

What about Spectrum edge connectors, I wonder if they are still available from retro sellers? Proper ones would have a key / contact missing but I seem to remember some that I saw being sold as Spectrum connectors in the recent past were not actually keyed.

Edit: I see you're ahead of me again - not keyed, bad news for Spectrum owners but good news for MK14 owners, I'd just have to carefully cut the ends open. Good spot. I've just grabbed a couple.

Last edited by SiriusHardware; 21st May 2020 at 11:24 pm.
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Old 21st May 2020, 11:35 pm   #410
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Default Re: MK14 schematic revisions

You may only have to cut the one end - on my JMP board I have one end enclosed on the little adapter I made to connect up my Cassette Interface, provide Power and allow me to jumper on the single step and any other oddments...

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Old 21st May 2020, 11:44 pm   #411
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Default Re: MK14 schematic revisions

I'll bear that in mind, thanks for pointing that out, otherwise I would have sliced out both ends without even looking. For the 16-way one I managed to find someone selling one of the aforementioned RS ones as new old stock, but unfortunately they only had one, which I bought.

I also found some of those on a site called 'AudioJumble' which seems to have a good range of connectors, but unfortunately it is closed at the moment for personal reasons.
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Old 22nd May 2020, 8:15 am   #412
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Default Re: MK14 schematic revisions

You could correct the 'wrong' position of the XCLOCK signal by cutting short the pins on the DIN connector on the MK14 and using a short piece of wire to connect the signal to the correct side. The other 30 pins should hold the connector in place. In retrospect I probably should have routed XCLOCK to the correct pin and not worried about accidentally shorting the clock.
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Old 22nd May 2020, 8:26 am   #413
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Default Re: MK14 schematic revisions

If you mean, should you have put the clock in the middle of all those 0V fingers on the top side - no I don't think so because that would alter one of the existing / established connections present on all other MK14s and make yours different from those, whereas, as things stand you have done a good job of making sure that all connections shared with other MK14s are identical. That is as it should be.

Yes, I could do as you suggest, I suppose the DIN connector is expendable in a way that the VDU PCB itself isn't.

There's one other problem isn't there, one of the configuration inputs on the VDU goes to INT (also an input) on the MK14 if connected one to one. I'd have to sort that out as well. Are we agreed about what we intend to do with that so we all sort it out the same way?
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Old 22nd May 2020, 11:40 am   #414
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Default Re: MK14 schematic revisions

TBH since I don't have a Sinclair VDU I'd rather someone who does to make that decision.
I noticed on our favourite auction site there's someone selling the character generator IC (the correct CAB version) a week ago which would make a replica easier.
I'm tempted.....
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Old 22nd May 2020, 11:56 am   #415
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Default Re: MK14 schematic revisions

I assume that even you would probably just buy one of the Czech VDU replica PCBs since that PCB doesn't really need to be improved - unless radically so, by adding onboard RAM mapped at 0200-> so it doesn't have to steal RAM from the system.

You don't actually need the char generator, the VDU will still give you a pixel graphics display without one. It obviously is needed if you want to display text.

It's just a question of deciding what line to take that VDU input to instead of MK14 'INT', and all agreeing on the same alternative.
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Old 22nd May 2020, 1:15 pm   #416
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Quote:
Originally Posted by SiriusHardware View Post
I assume that even you would probably just buy one of the Czech VDU replica PCBs since that PCB doesn't really need to be improved - unless radically so, by adding onboard RAM mapped at 0200-> so it doesn't have to steal RAM from the system.
Your right I'd probably do that, my project list is already longer than I'd like and I here the Czech VDU is a pretty good replica.
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Old 24th May 2020, 11:12 am   #417
Slothie
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Default Re: MK14 schematic revisions

Neat circuit from a National publication to emulate the character generator that might be handy posted to the BUS thread.
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Old 27th May 2020, 7:31 pm   #418
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Default Re: MK14 schematic revisions

Tim: better hurry up with that SCRUMPI...
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Old 27th May 2020, 7:48 pm   #419
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Default Re: MK14 schematic revisions

Quote:
Originally Posted by SiriusHardware View Post
Tim: better hurry up with that SCRUMPI...
It is finished and running - just working out how the latch chip works and converting 1d LIFE to it as an exercise. My set of Keys with Green and Clear covers arrived today (Two sets luckily as I am using the same for the SCRUMPI3 Keyboard rebuild...)

I have all the other components ready for the board as the 7408's came and test OK on both my quick tester and my EPROM programmer. As you pointed out I have a good stock of displays... Just waiting on replacement 74LS00 for my VDU kit but, I have one ready for the MK14 V6 which will need to be built and working first.

Is that a real one? Did they arrive? - if so they look beautiful.
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Old 27th May 2020, 8:01 pm   #420
Slothie
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Quote:
Originally Posted by SiriusHardware View Post
Tim: better hurry up with that SCRUMPI...
Ooh black very nice!
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