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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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18th Nov 2022, 12:23 pm | #21 | |
Dekatron
Join Date: Aug 2011
Location: Newcastle, Tyne and Wear, UK.
Posts: 11,587
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Re: Unbuilt original MK14 VDU
Quote:
You could probably lose the modulator and convert the output circuit to a 75R composite video buffer as well, since people are more likely to use / need that type of connection. |
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18th Nov 2022, 8:03 pm | #22 |
Octode
Join Date: Mar 2019
Location: Barry, Vale of Glamorgan, Wales, UK.
Posts: 1,364
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Re: Unbuilt original MK14 VDU
Perhaps a component layout under the space for a modulator to allow an alternate fit for those who want the look - or even just as is done on other machines hollow out the Modulator to be the composite just soldered to a different hole next to the one suitable for the modulator.
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18th Nov 2022, 9:41 pm | #23 |
Dekatron
Join Date: Aug 2011
Location: Newcastle, Tyne and Wear, UK.
Posts: 11,587
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Re: Unbuilt original MK14 VDU
That would involve vandalising a 40+ year old modulator although it is reversible if carefully done (and indeed is commonly done). Great idea to put the trackwork for the components for composite-out entirely within the outline which would be occupied by the modulator though. By the same token you could also put the TOP PAGE series resistor in the hollow between the sides of one of the IC sockets so that it would be hidden when the IC and socket were fitted.
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9th Dec 2022, 8:41 pm | #24 | |
Triode
Join Date: Nov 2022
Location: Newport, Monmouthshire, Wales, UK.
Posts: 16
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Re: Unbuilt original MK14 VDU
Quote:
It is a nearly exact copy of the original and the IC leg holes and about 95% of the vias perfectly line up if you hold the boards together. The attached photo shows the original on the left and the reproduction on the right https://www.8bity.cz/2018/mk14-vdu-v...-unit-replica/ |
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9th Dec 2022, 9:41 pm | #25 |
Dekatron
Join Date: Aug 2011
Location: Newcastle, Tyne and Wear, UK.
Posts: 11,587
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Re: Unbuilt original MK14 VDU
Thanks for letting us know - as a matter of interest do you know if Martin still has full kits available? Not asking for myself of course but I remember that all you needed was the PCB, others may still.be interested in complete kits.
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9th Dec 2022, 10:28 pm | #26 |
Triode
Join Date: Nov 2022
Location: Newport, Monmouthshire, Wales, UK.
Posts: 16
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Re: Unbuilt original MK14 VDU
The list he sent was PCBs for all his designs: MK14/VDU/Cassette/ROMRAM plus switches, foils and PROMS for his MK14 board.
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10th Dec 2022, 2:43 pm | #27 |
Hexode
Join Date: Jan 2021
Location: Ashford, Kent, UK
Posts: 318
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Re: Unbuilt original MK14 VDU
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10th Dec 2022, 10:04 pm | #28 | |
Triode
Join Date: Nov 2022
Location: Newport, Monmouthshire, Wales, UK.
Posts: 16
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Re: Unbuilt original MK14 VDU
Quote:
(View that page in the original czech language as the translator messes the email address up a bit) |
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2nd Jan 2023, 6:33 am | #29 | |
Triode
Join Date: Jul 2017
Location: Fairfield, Melbourne, Australia
Posts: 48
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Re: Unbuilt original MK14 VDU
Quote:
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2nd Jan 2023, 8:36 am | #30 |
Octode
Join Date: Mar 2020
Location: Kitchener, Ontario, Canada
Posts: 1,298
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Re: Unbuilt original MK14 VDU
11% overclocked is not even close to the maximum.
I have been able to run a few samples at 9 MHz in Slothie’s issue VI replica running the SoC monitor. I didn’t find one that wouldn’t run at 8 MHz. If you are latching the upper address bits then you need to latch on the rising edge of NADS or use a transparent latch. I’d recommend 74hct193. |
2nd Jan 2023, 7:25 pm | #31 | |
Dekatron
Join Date: Aug 2011
Location: Newcastle, Tyne and Wear, UK.
Posts: 11,587
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Re: Unbuilt original MK14 VDU
Quote:
As Mark said, though, he has had his cranked up to quite a bit higher... |
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3rd Jan 2023, 2:32 pm | #32 | |
Triode
Join Date: Jul 2017
Location: Fairfield, Melbourne, Australia
Posts: 48
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Re: Unbuilt original MK14 VDU
Quote:
At 8 MHz we might get some processing done . Does cooling or fooling about with Vcc help much? I was planning to use either 'LS573 or 'LS574. In this particular case there didn't seem to be much difference in the outcome for A12..15. (I'm choosing LS because they are already on hand.) One has to invert NADS either way. Planning on a Dallas DS1233-5 for the NRST line so it can be driven from the bus side if needs be. Thanks, Brian. |
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3rd Jan 2023, 6:05 pm | #33 |
Octode
Join Date: Mar 2020
Location: Kitchener, Ontario, Canada
Posts: 1,298
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Re: Unbuilt original MK14 VDU
Just run the sc/mp at 7.3728 MHz
Use the 573 if thats the only choice between 573 or 574. 193 doesn’t need to invert NADS. 192 would probably also work. Ground the clock inputs to disable counting and you can also use the carry and borrow outputs as decoded 4k address pages for IO or ROM. |
4th Jan 2023, 9:00 am | #34 | |
Triode
Join Date: Jul 2017
Location: Fairfield, Melbourne, Australia
Posts: 48
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Re: Unbuilt original MK14 VDU
Quote:
Indeed, running at 7.3728 MHz will be fine for initial testing, with jumper options for 3.6864 MHz and 1.8432 MHz as well. Maybe swap the 'LS74 for a 'HC393 with a 'HCT14 for level translation from the can oscillator. More stages, more flexibility. |
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4th Jan 2023, 12:07 pm | #35 |
Octode
Join Date: Mar 2011
Location: North Yorkshire, UK.
Posts: 1,119
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Re: Unbuilt original MK14 VDU
Now thats clever, I hadnt seen the use of a 193 presettable counter as a SC/MP address latch. You scampers should get together and write a book before all this knowledge is lost!
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