5th Jul 2020, 11:32 am | #361 | ||
Octode
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Re: Recreating the Bywood Scrumpi
Quote:
For those following he also used the upper section of the 7474 so it is Pin 11 that is connected to Pin 3 on the 555 not 3 as on ours. The slight change that r1 in the astable (provided by R5 at 47K) makes is to lengthen the Ton to 3.6ms from 0.65ms with Toff remaining at 0.32ms which means the Slow step frequency remains around 1Hz. I will swap one of mine out and prove it still works or what if any impact it has on the single step especially. On our board that means swapping R4 for a 47K. |
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5th Jul 2020, 11:42 am | #362 | |
Octode
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Re: Recreating the Bywood Scrumpi
Quote:
On the JMK point it is why I have been driven to do this. I also agree that the BYWOOD ads did look unprofessional - and perhaps it was that human and "not polished" look that attracted me to them BITD as a hobby constructor - I was obviously eventually swayed by the eventual ZX80 slick colour advertising on what I did. It reminds me very much of my own early journey I suppose as our early adverts and inlays were definitely on the BYWOOD side with art drawn by school friends or even me but, we did strive for the SoC/Sinclair approach by the end with slick professional artwork. |
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5th Jul 2020, 11:52 am | #363 | |
Octode
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Re: Recreating the Bywood Scrumpi
Quote:
Last edited by Timbucus; 5th Jul 2020 at 11:53 am. Reason: minor typo |
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5th Jul 2020, 3:29 pm | #364 |
Rest in Peace
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Re: Recreating the Bywood Scrumpi
I've noticed something that is probably a US phenomenon: addition of a current loop interface to something like a Mark 8 (an early switches and LEDs machine) to enable it to drive a teletype. Add some memory and you could be running BASIC on said machine.
I can't see that expansion path ever working in the UK. Who in the 1970s owned a teletype? Or any kind of terminal for that matter? No, a BASIC-capable machine for the UK market just had to have a built-in keyboard and VDU, and that meant a big cost jump. So who were buying the systems with current loop interfaces on them? |
5th Jul 2020, 4:10 pm | #365 |
Pentode
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Re: Recreating the Bywood Scrumpi
yes nostalgia when you hold us what an epic.
let us return to our machine no problem of voltage CMOS.j uses a 74c74 and I am in the process of realizing the pcb to the exact copy. in fact it is the second flip-flop that is used the input D is at +VCC R11 is the pullup of RUN/HALT CS4 and R8 is the pullup of SLOW and STEP CS2/CS3 I make some tests on my board to check the resistance underneath to an unknown function and the pullup of the NE555 output is useless but I'll test with without of course the plan is not complete in the brochure. Amateur hour is in the air. |
5th Jul 2020, 4:10 pm | #366 |
Octode
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Re: Recreating the Bywood Scrumpi
I imagine a lot of colleges would have teletypes and American electronics magazines had numerous TV Typewriter and VDU projects. I had a GE Terminet 300 Teketype in 1980 my father rescued from a skip when they were upgrading to VT100s so I imagine other hobbiests did. I interfaced it to my PET to use as a printer.
But you're right, home computers only really took off when they had TV interfaces and built in keyboard. |
5th Jul 2020, 4:11 pm | #367 |
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Re: Recreating the Bywood Scrumpi
there's amateur hour in the air.
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5th Jul 2020, 4:45 pm | #368 |
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Re: Recreating the Bywood Scrumpi
Tim, you must be happy.
in my youth as a DIY ADO I was reading the magazines. the scrumpi had caught my eye and I liked the mk14 very much. I had considered ordering a zx80 and then the time spent on a zx81 kit but each time my pocket money was very low and I waited by making different assemblies with salvaged parts. finally I transformed my TI30 in high school into a programmable machine the whole in a wooden box with RAM multiplexer demultiplexer keyboard and switch for programming step by step not a jewel for me my. Industrial design teacher was not coming back unfortunately I'm no longer this machine and I can not find the plans that I had modified and adapted to my project. my first computer was a VIC20 |
5th Jul 2020, 6:49 pm | #369 | |
Octode
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Re: Recreating the Bywood Scrumpi
Quote:
The only place I saw terminals was school and college - I cannot remember anyone I know having one - it was that move to things like the NASCOM having a BASIC and a keyboard/VDU that moved computing in the UK to the mainstream you are correct. |
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5th Jul 2020, 8:25 pm | #370 |
Dekatron
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Re: Recreating the Bywood Scrumpi
Two posts deleted. Unsolicited eBay listing.
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6th Jul 2020, 5:57 pm | #371 |
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Re: Recreating the Bywood Scrumpi
sorry
the pcb's have arrived |
6th Jul 2020, 6:06 pm | #372 |
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Re: Recreating the Bywood Scrumpi
the tests to correct the circuit as the original are finished the bywood plan is ok but still to redo the pcb
mike's welded-on resistor is useless. |
6th Jul 2020, 9:12 pm | #373 |
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Re: Recreating the Bywood Scrumpi
They look really cool - I also had a nice delivery today...
and some 3mm LED's with resistance are on order - I am NOT soldering resistors to 20 LED legs ever again! Interesting that the pullup on the underneath is not needed on the flip flop - perhaps DJD just misunderstood when he drew his circuit showing R5 going to the wrong pin. I assume the input must float high as it is a CMOS device - maybe a different result on LS - I will remove mine and test when I get five minutes. I have still not tested a 47K resistor yet - life has been a bit busy. |
7th Jul 2020, 2:40 pm | #374 |
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Re: Recreating the Bywood Scrumpi
tim
I just sent you the tim/phil pcb's.:pouces vers le haut: The holes are big enough for the SPDT switch.:pouces vers le haut: easy to find on our favourite sites. I have tested everything as a bywood 47k 10 µf version etc.: rire2: D rocker etc. everything works wonderfully think about making a power supply in the style of mine 2x12V 10VA 7805 TO3 7912 -12v and lm337 -7v I may add the -9v to it.:idée: |
7th Jul 2020, 2:41 pm | #375 |
Pentode
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Re: Recreating the Bywood Scrumpi
see
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8th Jul 2020, 9:17 pm | #376 |
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Re: Recreating the Bywood Scrumpi
see
but it's a version that's not like the original. but it works |
9th Jul 2020, 8:36 pm | #377 |
Octode
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Re: Recreating the Bywood Scrumpi
Wow Phil that looks really lovely - I'm very impressed - the switches make all the difference...
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9th Jul 2020, 9:15 pm | #378 |
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Re: Recreating the Bywood Scrumpi
That is a very nice replica, and tribute to a piece of history that is largely forgotten. I'm kinda tempted myself
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9th Jul 2020, 11:03 pm | #379 |
Pentode
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Re: Recreating the Bywood Scrumpi
tim, you'll be receiving the beta version of the pcb's soon.
there is a pcb for KAREN and SLOTHIE and a surprise we'll talk about it in MP Thanks karen but it's still not the version like the original. I reworked the pcb but I'm having fun with our beta version. I'm already thinking of some extension. when jim will want to contact me can be a scrumpi2 project. but with TIM we are going to focus on the scrumpi3 project 2020/2021 |
10th Jul 2020, 5:41 pm | #380 |
Octode
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Re: Recreating the Bywood Scrumpi
Well - they did arrive today Phil - amazing collection thank you so much - I will chat on PM about the other boards.
Silly me I ordered Switches with tags on again like for the prototype - I will have to wait until my PCB ones arrive to build mine! Karen, I will forward on the boards to you - that PMOS CPU of yours deserves to be on one of these... |