Power Supply switching between ZX81 & Speccy

Discussions about Sinclair ZX80 and ZX81 Hardware
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RetroMike
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Joined: Mon Jun 09, 2014 1:33 am

Re: Power Supply switching between ZX81 & Speccy

Post by RetroMike »

Interesting stuff... well hopefully our computer room won't have any massive shifts in temperature or humidity like you describe ;)
gozzo wrote:.. 'shifting' interference????.....
Kind of like formation dancing of ants on the screen. Is that what people mean when they say "dot crawl"?
balford
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Re: Power Supply switching between ZX81 & Speccy

Post by balford »

Yes, that sounds like dot crawl. An explanation and video available here.
gozzo
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Re: Power Supply switching between ZX81 & Speccy

Post by gozzo »

Aha, yes that infamous dot crawl!!...wish someone would come up with a way to eliminate it - easily, I have a 'possible' idea but is horrendously complex!
gozzo
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Re: Power Supply switching between ZX81 & Speccy

Post by gozzo »

Are you using 'original' RF connection or composite mod? (note that the composite signal IS available on the edge connector, no need to mutilate that poor modulator ;) )
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RetroMike
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Re: Power Supply switching between ZX81 & Speccy

Post by RetroMike »

Composite mod with a 100uf cap in the circuit :) I've just had a tip on WOS to replace TR1 & 2, and install some 1uf caps in C5-8 to reduce the effects of the crawl, and will see whether it dwindles sufficiently when that's done ;)
redgatemodels
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Re: Power Supply switching between ZX81 & Speccy

Post by redgatemodels »

Bookmarked the info about the mod cable, but IS it possible to fit a 2.1mm socket to an ‘81 pcb?
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1024MAK
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Re: Power Supply switching between ZX81 & Speccy

Post by 1024MAK »

Yes, it’s possible. Mainly because nothing is impossible…

But it’s highly unlikely that you will find one with the same pin arrangement. So you would have to use wires to connect the new 2.1mm barrel socket to the PCB pads and a suitable glue to hold the new socket in position.

Mark
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Paul
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Re: Power Supply switching between ZX81 & Speccy

Post by Paul »

There is no harm in having a dedicated PSU for every computer you own.
Your are not using your laptop PSU with your PC, are you? :ugeek:
In theory, there is no difference between theory and practice. But, in practice, there is.
redgatemodels
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Re: Power Supply switching between ZX81 & Speccy

Post by redgatemodels »

Who has a pc these days? :D ;)

Only joking, but we’ve not had one in the house for about 8 years. #1 son has a current spec iPad Pro, #2 son has an ancient Lenovo thinkpad which he shares with me (it runs DesignSpark pcb etc). Wife has a dell laptop. Me? Old iPad air2 and a nice new surface laptop (work supplied)
redgatemodels
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Re: Power Supply switching between ZX81 & Speccy

Post by redgatemodels »

1024MAK wrote: Sat Sep 30, 2023 2:02 am Yes, it’s possible. Mainly because nothing is impossible…

But it’s highly unlikely that you will find one with the same pin arrangement. So you would have to use wires to connect the new 2.1mm barrel socket to the PCB pads and a suitable glue to hold the new socket in position.

Mark
Cheers Mark, I’ll probably stick to an adaptor lead if I pick up a zeddy without a psu. I’ve not actually got one at the moment, my old one did not turn up when clearing the loft. There is a chance it’s stashed elsewhere, but it probably got wanged. Seem to remember I broke it adding more and more mods…….
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