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Old 21st Jan 2019, 8:12 pm   #41
wireless_john
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Default Re: Retro computer homebrew: Orton Karenbak-1 computer

Yes, I'd considered that too. If I can't get the AND gates to look and work to my satisfaction, then ganging two 3P4W is next!

Thanks - John
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Old 21st Jan 2019, 11:34 pm   #42
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Default Re: Retro computer homebrew: Orton Karenbak-1 computer

"I remember something called 'Nylese' from many years ago. It too was stripped by the heat of the iron. Burning plastic fumes - now that's GOT to be unhealthy!" post #19


I once wired up 66 TTL's with wire wrap wire, but I chose to strip & solder each connection, so there was no burning. Firstly I ran the power rails down the long axis under each IC and fitted the bypass caps.

There are over 900 connections and I realized it would be a major issue to keep them orderly. I used as many direct surface links as possible with bare wire. I also routed the wires in bundles down the long axis of the IC's and laced them up with surgical silk thread, you can just see it in the photo. The method allowed for continued access to the IC pins for easy soldering. If its a rats nest instead, it becomes difficult to get at the pins.

photo attached.
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Old 22nd Jan 2019, 12:19 pm   #43
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Default Re: Retro computer homebrew: Orton Karenbak-1 computer

How about pushbuttons a CD4532 to encode them then a couple of analogue switch IC's - they should be fast enough?

D
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Old 22nd Jan 2019, 5:16 pm   #44
Karen O
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Default Re: Retro computer homebrew: Orton Karenbak-1 computer

The switch is a bit unusual. My projects are not specified, and the final result is ultimately dependent on what I have in my parts store (a euphemism for rows of boxes containing scrap PCBs!). I salvaged my switch from such a PCB. Having that switch greatly influenced the design. If not for that switch, I might still be ruminating over building a micro-less computer.

I just wish I'd checked whether it was break-before-make
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Old 22nd Jan 2019, 6:53 pm   #45
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Default Re: Retro computer homebrew: Orton Karenbak-1 computer

Thanks for all your suggestions. I'm still working on it !

John
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Old 25th Jan 2019, 6:13 pm   #46
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Default Re: Retro computer homebrew: Orton Karenbak-1 computer

Spent a fair bit of time working on this! The attached PDF is my latest attempt at replacing the 5P4W switch with a SP4W switch and some logic. Haven't double checked it, but I think it's right. The page is divided in to rows, each row representing one pole.

After many attempts I've got it down to five ICs (from seven) which fits well with the five columns of ICs on Karens logic PCB. One on the end of each column. Losing another IC will be the focus of any more attempts to simplify it, rather than just saving a gate. Saving one AND gate or the three input OR gate would be good! That will save a whole IC.

Anyway, I'm not a professional logic designer but I recognise that some switch positions will leave floating inputs. I think the answer here is pull-down resistors but not too sure what values. 10k? Is that right?

Any comments/advice from the experts welcome.

Thanks.
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Old 25th Jan 2019, 7:00 pm   #47
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Default Re: Retro computer homebrew: Orton Karenbak-1 computer

While I am impressed by Karen's computer and her proficiency, I do have to ask:

What can you use such a machine for? Is it a kind of calculator?

Obviously I don't know anything about such things
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Old 25th Jan 2019, 7:52 pm   #48
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Default Re: Retro computer homebrew: Orton Karenbak-1 computer

Hi John,

10k pull-downs will work with HC/HCT logic but a bit of a no-no on LS gates. I forget what current emerges from a low LS input - 400uA...? You have to pull it down to at least 0.5V and that demands a low value resistor - around 1k if I've got my Iout(LOW) right.
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Old 25th Jan 2019, 8:12 pm   #49
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Default Re: Retro computer homebrew: Orton Karenbak-1 computer

Quote:
Originally Posted by Hampus View Post
While I am impressed by Karen's computer and her proficiency, I do have to ask:

What can you use such a machine for? Is it a kind of calculator?

Obviously I don't know anything about such things
I imagine it's just an exercise done for its own sake. You could emulate the functionality in software reasonably easily on a PC or Raspberry Pi. Some people just like hacking hardware though
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Old 25th Jan 2019, 10:56 pm   #50
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Default Re: Retro computer homebrew: Orton Karenbak-1 computer

That's right - no obvious use for it - I just like it!

John
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Old 25th Jan 2019, 11:02 pm   #51
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Default Re: Retro computer homebrew: Orton Karenbak-1 computer

Quote:
Originally Posted by Karen O View Post
Hi John,

10k pull-downs will work with HC/HCT logic but a bit of a no-no on LS gates. I forget what current emerges from a low LS input - 400uA...? You have to pull it down to at least 0.5V and that demands a low value resistor - around 1k if I've got my Iout(LOW) right.
Thanks Karen

John
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