ZX81 rebuild

Discussions about Sinclair ZX80 and ZX81 Hardware
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1024MAK
Posts: 5103
Joined: Mon Sep 26, 2011 10:56 am
Location: Looking forward to summer in Somerset, UK...

Re: ZX81 rebuild

Post by 1024MAK »

Oscillator design is one of the parts of electronics that is considered a black science!

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.
Lardo Boffin
Posts: 2160
Joined: Sat Nov 26, 2016 2:42 am

Re: ZX81 rebuild

Post by Lardo Boffin »

Oh good. At least it is an easy one to sort then.

Maybe one of these?

https://www.cricklewoodelectronics.com/SFE6M5.html

Not much detail on their site though.
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
Posts: 5103
Joined: Mon Sep 26, 2011 10:56 am
Location: Looking forward to summer in Somerset, UK...

Re: ZX81 rebuild

Post by 1024MAK »

Other 'black arts' in electronics include switch-mode power supply systems and boost and buck DC-DC converters... (well, before special 'easy to use' chip came on the market).

As to which is the most suitable ceramic resonator, it's a case of buy it and try it as far as I can tell. The normal use of these is as part of a filter circuit, not as oscillators.

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.
krowne
Posts: 10
Joined: Wed Nov 09, 2016 5:44 pm
Location: Chester, Cheshire

Re: ZX81 rebuild

Post by krowne »

Lardo Boffin wrote: Tue Feb 06, 2018 7:53 pm Oh good. At least it is an easy one to sort then.

Maybe one of these?

https://www.cricklewoodelectronics.com/SFE6M5.html

Not much detail on their site though.
Lardo PokeMon has them on S.M.R.

https://www.sellmyretro.com/offer/details/3469
Brian
Lardo Boffin
Posts: 2160
Joined: Sat Nov 26, 2016 2:42 am

Re: ZX81 rebuild

Post by Lardo Boffin »

Thanks!
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
Lardo Boffin
Posts: 2160
Joined: Sat Nov 26, 2016 2:42 am

Re: ZX81 rebuild

Post by Lardo Boffin »

Well, after a brief pause to move house (if only the builders had finished it before we moved in :evil: ) I have finally got back to this!

I fitted a turned pin socket for the oscillator and put in an original zeddy one:-

D79CD3CB-BA24-4A3C-B0ED-6DC0B5CED185.jpeg

Its alive!!! :lol:
And yes I have been relegated to the garage. Something to do with melting holes in worksurfaces...

60F52597-E256-4F42-9C8B-FDFBB16394C7.jpeg
Bouyed up by this I fitted a new one from Sell My Retro and....
7A3CBDB3-3C0A-4939-9321-C9E9BC30A700.jpeg

Still alive! I have a new ROM and hopefully a new ULA from Andy at some point at which time the only original component will be the PCB and case. Hmmmm....
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
User avatar
1024MAK
Posts: 5103
Joined: Mon Sep 26, 2011 10:56 am
Location: Looking forward to summer in Somerset, UK...

Re: ZX81 rebuild

Post by 1024MAK »

Image
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.
McKlaud
Posts: 337
Joined: Tue Dec 19, 2017 10:02 pm
Location: St Albans, UK

Re: ZX81 rebuild

Post by McKlaud »

:geek: well done, well done :geek:
Claudius
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Lardo Boffin
Posts: 2160
Joined: Sat Nov 26, 2016 2:42 am

Re: ZX81 rebuild

Post by Lardo Boffin »

McKlaud wrote: Thu Jul 05, 2018 9:06 pm :geek: well done, well done :geek:
Thanks. One of your ROMs will be going into it!
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
Moggy
Posts: 3231
Joined: Wed Jun 18, 2008 2:00 pm

Re: ZX81 rebuild

Post by Moggy »

Lardo Boffin wrote: Thu Jul 05, 2018 9:20 pm
McKlaud wrote: Thu Jul 05, 2018 9:06 pm :geek: well done, well done :geek:
Thanks. One of your ROMs will be going into it!
Hopefully not the X2 ROM (it's packed with C-4 and a certain keypress combination sets it off) :lol:

Apologies it's whisky night.
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