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Old 15th Jan 2019, 11:10 pm   #21
Wendymott
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Default Re: Retro computer homebrew: Orton Karenbak-1 computer

Hi Karen... back to that "old" chestnut..to minimise solder fumes as you say as with pvc coating fumes.. I have a small Ex puter fan fixed to the bench blowing air across my face..sometimes I forget to switch it on.."age"
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Old 16th Jan 2019, 12:40 am   #22
Karen O
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Default Re: Retro computer homebrew: Orton Karenbak-1 computer

Hi Wendy,

My use of Nylese goes back some thirty-five years.

I was an incorrigible youth back then

Now I've got a growing list of ailments to remind me that I'm not indestructible.
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Old 18th Jan 2019, 10:20 am   #23
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Default Re: Retro computer homebrew: Orton Karenbak-1 computer

OK, Ive got the wiring pen and spools and a suitable piece of single sided copper clad board. I might still get a Eurocard though - it'll save a lot of centre popping and drilling!

Then I'll have to sort through my boxes of IC's - that might take longer!

John
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Old 18th Jan 2019, 3:17 pm   #24
Karen O
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Default Re: Retro computer homebrew: Orton Karenbak-1 computer

Blimey! Drilling copper clad board for twenty-five ICs sounds like hard work. I could never get the spacing even enough, resulting in my IC sockets refusing to seat

But don't listen to me. This is someone who wanted plain perf board so etched away the copper on some vero board!
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Old 18th Jan 2019, 4:13 pm   #25
dominicbeesley
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Default Re: Retro computer homebrew: Orton Karenbak-1 computer

If you don't mind the expense I can recommend these boards http://www.roadrunnerelectronics.com...Boards/Oktapad

The are very well made, have nice pads and stand up to heat well. I've tried cheaper ones but to get the enamel to melt you need the iron HOT and when prototyping I end up re-doing joints over and over ending in lifted pads. The reverse has a nice ground plane too.

I can also recommend their wiring pens (and kits) the wiring pen has a metal nozzle (rather than the plastic one on the vero which I, of course, quickly melted!)

The also do the combs but I didn't bother with them and went rat's nest as this was a "make it up as you go along" project...https://stardot.org.uk/forums/viewto...=15350#p210135

D
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Old 18th Jan 2019, 4:28 pm   #26
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Default Re: Retro computer homebrew: Orton Karenbak-1 computer

Thanks for that! I've been through my TTL box and very few HC IC's. I've got plenty of LS though. They should be OK shouldn't they? Just a bit more power?

On the spreadsheet, the ones highlighted in red are the LS versions of the HC ones in the computer.

I don't mind the drilling so much as centre popping all the drilling positions through 0.1" squared paper! One dodgy hit and it all goes wrong - you can't re do it!

John
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Old 18th Jan 2019, 4:35 pm   #27
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Default Re: Retro computer homebrew: Orton Karenbak-1 computer

Quote:
Originally Posted by dominicbeesley View Post
I can also recommend their wiring pens (and kits) the wiring pen has a metal nozzle (rather than the plastic one on the vero which I, of course, quickly melted!)
I usually wrap the wire round the pin a few times, then snip it off with a pair of scissors. Then I solder it so the soldering iron never gets near the plastic tip.

John
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Old 18th Jan 2019, 4:40 pm   #28
dominicbeesley
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Default Re: Retro computer homebrew: Orton Karenbak-1 computer

I must be more cack-handed I found it always jumped off unless I got it soldered quickly!

I'll be interested to see how you get on. Do keep posting pics.

I am playing with the idea of recreating one of these in an FPGA or CPLD but I suspect that will end up with all my other half started projects!

D
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Old 18th Jan 2019, 4:57 pm   #29
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Default Re: Retro computer homebrew: Orton Karenbak-1 computer

Somebody called Lawrence Wilkinson did that - emulated an IBM 360 in an FPGA. I met him at Bletchley Park about 10 years ago.

http://www.ljw.me.uk/ibm360/vhdl/

Well over my head!!

John
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Old 18th Jan 2019, 5:47 pm   #30
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Default Re: Retro computer homebrew: Orton Karenbak-1 computer

Karen, I've spent all afternoon on this looking at components etc and what I have in my junk boxes.

1. I have most of the ICs but not HC family, only LS types. They should work OK do you think, at the expense of a bit more power?

2. I don't have 74LS4040 IC 7 and 17, and they don't seem to exist. 74HC4040 seems readily available so is it OK to mix them with 74LS ?

I already have a nice project box in my "come in handy" pile. Looks like it finally has!

Regards

John
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Old 18th Jan 2019, 5:51 pm   #31
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Default Re: Retro computer homebrew: Orton Karenbak-1 computer

I'll second the recomendation for the Roadrunner wiring pen. It's very useful for one-off projects like this.

As for drilling holes for an IC socket in copperclad board, I used an odd bit of stripboard as a drilling jig.

At one time you could get a tool that consisted of a drill bit with a cylindrical cutter round it. It drilled the hole and then cut away the copper leaving a nice circular pad round the hole. No idea where you'd get one now.
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Old 18th Jan 2019, 7:17 pm   #32
Karen O
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Default Re: Retro computer homebrew: Orton Karenbak-1 computer

Hi John,

You can mix LS TTL and HCMOS but you have to add pull-up resistors wherever an LS output drives a HCMOS input. Bear in mind that some HCMOS gates are Schmitt triggers and are used for generating delays.
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Old 18th Jan 2019, 7:43 pm   #33
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Default Re: Retro computer homebrew: Orton Karenbak-1 computer

I remember the IC pin number labels for the back too, mirror image of course.
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Old 18th Jan 2019, 10:32 pm   #34
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Default Re: Retro computer homebrew: Orton Karenbak-1 computer

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I remember the IC pin number labels for the back too, mirror image of course.
Something you learn the hard way!!

John
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Old 19th Jan 2019, 5:41 pm   #35
wireless_john
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Default Re: Retro computer homebrew: Orton Karenbak-1 computer

The MODE control appears to be a 5 pole 4 way rotary switch. Is there such a thing?
I found a 6P4W on Farnell and it was 69!!

I haven't been able to find one so far.

John
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Old 20th Jan 2019, 10:55 am   #36
wireless_john
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Default Re: Retro computer homebrew: Orton Karenbak-1 computer

Well, that switch has turned in to a bit of a show stopper. Can't seem to get one anywhere without spending a lot of money, which I don't want to do.

I was hoping to build it with bits from my junk boxes, and I do have most of it. If nothing else, I've been through all my logic IC's now!

Back burner for now, till I see a suitable switch somewhere.

John
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Old 20th Jan 2019, 12:15 pm   #37
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Default Re: Retro computer homebrew: Orton Karenbak-1 computer

Rs and others used to make a stackable selector switch 1 long shaft and i seem to remember single pole 12 way wafers you just added as many wafers as poles required
have you looked at this
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Old 20th Jan 2019, 1:48 pm   #38
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Default Re: Retro computer homebrew: Orton Karenbak-1 computer

I remember those switches from RS. They were called 'Makaswitch' or some similar term and came in 2 sizes. The switch wafers had 12 fixed contacts and existed in single pole, 12 way, 2 pole 6 way, 3 pole 4 way and 4 pole 3 way I think. There were also screening plates, spacers, a mains-rated switch, etc.

But getting back to the problem. The switch here seems to select logic signals. I think it would not be too much work to replace it with a handful of TTL ICs (AND gates, effectively) and a single pole switch.
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Old 21st Jan 2019, 9:08 am   #39
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Default Re: Retro computer homebrew: Orton Karenbak-1 computer

Hello Trevor, yes I had considered that and I remember the Makaswitch but they're more than I'm prepared to pay!

Tony, I think I'll be going along with your suggestion. I spent an hour looking at it yesterday and I think it could be done with three or four 74HC08 (Quad 2 input AND). I've got one, they're still quite cheap to buy and I have a 1P4W BBM rotary switch.

In the meantime, I'll keep my eyes open for a switch!

John
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Old 21st Jan 2019, 6:57 pm   #40
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Default Re: Retro computer homebrew: Orton Karenbak-1 computer

What about two 3 pole 4 way swithces, you will have to turn them together, join them with levers and a link (only goes +/- 60 degrees should be OK) or put them front to front and wire one backwards. Big edge knob for turning.
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