Zx81 ram pack

Discussions about Sinclair ZX80 and ZX81 Hardware
Mooseturker
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Joined: Sun Nov 21, 2021 10:32 am

Zx81 ram pack

Post by Mooseturker »

Hello
This is my first post so please go easy, I've just bought my 2nd zx81 nearly 40 years after the first which is long gone. It needs a new keyboard membrane and looking to buy a ram pack. Is there a particular type ram pack I should be looking out for and where do people source spares from now? Evil Bay, facebook or on here maybe?

Thanks for any advice
Trev
Lardo Boffin
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Joined: Sat Nov 26, 2016 2:42 am

Re: Zx81 ram pack

Post by Lardo Boffin »

Welcome Trev.

You can get RAM packs on evil bay but the prices vary wildly!

You could also do an internal 16K modification if feeling brave while replacing the keyboard.

Whereabouts in the world are you?

Lardo
ZX80
ZX81 iss 1 (bugged ROM, kludge fix, normal, rebuilt)
TS 1000 iss 3, ZXPand AY and +, ZX8-CCB, ZX-KDLX & ChromaSCART
Tatung 81 + Wespi
TS 1500 & 2000
Spectrum 16k (iss 1 s/n 862)
Spectrum 48ks plus a DIVMMC future and SPECTRA
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1024MAK
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Re: Zx81 ram pack

Post by 1024MAK »

Hello Trev and welcome :D

One other place to keep an eye on is Sell My Retro.

However, apart from used/preowned RAM packs (and as well as Sinclair, there are other makes, including Memotech), I’m not sure if anyone makes new units.

For people who don’t mind tinkering with electronics and who can solder, it’s possible to remove the existing on board RAM chip and fit a larger capacity RAM chip.

Ahh, our resident Del Boy Zeddy trader has got in before me!

Mark
ZX81 Variations
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Mooseturker
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Joined: Sun Nov 21, 2021 10:32 am

Re: Zx81 ram pack

Post by Mooseturker »

Excellent, cheers for the advice, I don't mind a tinker and onboard ram sounds like the go, i've just moved to Spain but still have an address in the uk where I'm putting a box of goodies together to bring over at some point, just need to make sure i have everything covered.
So next question is internal ram Ebay?

Cheers Again for the help and advice
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mrtinb
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Re: Zx81 ram pack

Post by mrtinb »

Kit for external 16k RAM £16.99 (through hole parts) https://www.ebay.com/itm/154639136618

Kit for internal 16k RAM £3.99 (SMD parts, RAM IC not included)
(Broken link: xhttps://xwww.ebay.com/itm/19446434799)
Updated 2022-02-23 xhttps://xwww.ebay.com/itm/194843852590
Updated 2023-02-27 https://www.ebay.com/itm/195613981839
Last edited by mrtinb on Mon Feb 27, 2023 3:46 pm, edited 4 times in total.
Martin
https://zx.rtin.be
ZX81, Lambda 8300, Commodore 64, Mac G4 Cube
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BarryN
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Re: Zx81 ram pack

Post by BarryN »

Mooseturker wrote: Sun Nov 21, 2021 9:42 pm Excellent, cheers for the advice, I don't mind a tinker and onboard ram sounds like the go, i've just moved to Spain but still have an address in the uk where I'm putting a box of goodies together to bring over at some point, just need to make sure i have everything covered.
So next question is internal ram Ebay?

Cheers Again for the help and advice
The other advantage to internal ram as opposed to a ram pack is that it will support high resolution WRX graphics although you can modify a ram pack to do that as well.
Lardo Boffin
Posts: 2160
Joined: Sat Nov 26, 2016 2:42 am

Re: Zx81 ram pack

Post by Lardo Boffin »

If you don’t mind track cutting and a few patch wires you can get away with just one of these and a socket:

23588B2F-7EFF-4B69-9CC8-F3E5E3A62E9F.jpeg

I have fitted a dozen or so of these (in between cleaning chandeliers badly).
ZX80
ZX81 iss 1 (bugged ROM, kludge fix, normal, rebuilt)
TS 1000 iss 3, ZXPand AY and +, ZX8-CCB, ZX-KDLX & ChromaSCART
Tatung 81 + Wespi
TS 1500 & 2000
Spectrum 16k (iss 1 s/n 862)
Spectrum 48ks plus a DIVMMC future and SPECTRA
albertusj
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Re: Zx81 ram pack

Post by albertusj »

My attempt. Also works on ZX81
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1024MAK
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Re: Zx81 ram pack

Post by 1024MAK »

For an issue one board, here’s a link to my blog page where I modify the board to upgrade the internal RAM to 16k bytes (using a single 32k byte SRAM chip).

Mark
ZX81 Variations
ZX81 Chip Pin-outs
ZX81 Video Transistor Buffer Amp

:!: Standby alert :!:
There are four lights!
Step up to red alert. Sir, are you absolutely sure? It does mean changing the bulb :!:
Looking forward to summer later in the year.
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BarryN
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Re: Zx81 ram pack

Post by BarryN »

1024MAK wrote: Mon Nov 22, 2021 1:47 pm For an issue one board, here’s a link to my blog page where I modify the board to upgrade the internal RAM to 16k bytes (using a single 32k byte SRAM chip).

Mark
Is it really that hard to make effective use of the other 16k as well?
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