"Different" ZX81's

Discussions about Sinclair ZX80 and ZX81 Hardware
Lardo Boffin
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Joined: Sat Nov 26, 2016 2:42 am

Re: "Different" ZX81's

Post by Lardo Boffin »

All things considered I think I am lucky to have a working ULA out of it!

Are the battery connectors soldered to the correct places does anyone know?
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
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1024MAK
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Re: "Different" ZX81's

Post by 1024MAK »

Yes, the wires look like they are connected to the correct points on the ZX81 circuit board. See picture:
ZX81 Issue 1 DC supply polarity - PCB track side
ZX81 Issue 1 DC supply polarity - PCB track side
ZX81 Issue 1 DC supply polarity - PCB track side.jpg (260.2 KiB) Viewed 4504 times
I do however recommend that a 1N4001 (or a 1N4002, 1N4003 ... 1N4007) diode is wired in series with the +V positive wire. See diagram:
Using a diode to provide polarity protection for a ZX81.jpg
Using a diode to provide polarity protection for a ZX81
(77.21 KiB) Downloaded 514 times
This will prevent damage if the input plugs are incorrectly connected ;)

Or you can use any reasonable sized cable with a 3.5mm mono jack plug like this:
ZX80, ZX81, TS1000 DC power input jack polarity
ZX80, ZX81, TS1000 DC power input jack polarity
ZX80, ZX81, TS1000 DC power input jack polarity.jpg (46.65 KiB) Viewed 4504 times
Mark
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sirmorris
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Re: "Different" ZX81's

Post by sirmorris »

Zeddies wired for 5V use are incompatible with an unmodified ZXpand. And some rampacks.

Not important, but noteworthy.
Lardo Boffin
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Re: "Different" ZX81's

Post by Lardo Boffin »

sirmorris wrote: Fri Jun 16, 2017 5:44 pm Zeddies wired for 5V use are incompatible with an unmodified ZXpand. And some rampacks.

Not important, but noteworthy.
If I do get round to making a zeddy laptop I am not carrrying a cassette player around so very pertinent information thanks.

This then leads to two questions:-

1) If 9 volts were used would that be ok?
2) What changes would be required to the ZXPand otherwise?

Thanks

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

Re: "Different" ZX81's

Post by Lardo Boffin »

1024MAK wrote: Fri Jun 16, 2017 5:06 pm Yes, the wires look like they are connected to the correct points on the ZX81 circuit board....
Mark
Thanks Mark!
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
sirmorris
Posts: 2811
Joined: Thu May 08, 2008 5:45 pm

Re: "Different" ZX81's

Post by sirmorris »

Lardo Boffin wrote: Fri Jun 16, 2017 7:15 pmIf I do get round to making a zeddy laptop

1) If 9 volts were used would that be ok?
2) What changes would be required to the ZXPand otherwise?
A1: Yes.
A2: I build 5V 'spands by leaving off the regulator and jumpering the 5v line on the edge connector to the regulator output pad. For a pre-existing 'spand you can either remove the regulator (quite hard) or cut its tracks/jumper the 5v.

A decent 5v supply should be able to supply both computer and xpansion.
Lardo Boffin
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Re: "Different" ZX81's

Post by Lardo Boffin »

I have not posted one of these for a while so here is the latest purchase. I think I may have missed one or two...

IMG_6342.JPG
(2.69 MiB) Downloaded 466 times

Another nice clean shiny issue one. This one came in a postal box rather than the usual printed box.

I'm not sure who CM is or why they chose to decorate the motherboard but I have seen a few with similar now.

At some point I may get one with the 4 major components with the same date stamp - I may have to keep that if I do!

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

Re: "Different" ZX81's

Post by Lardo Boffin »

And an issue 3. Not had one of those for a while!

In a nice sleeve type box.

IMG_6344.JPG
(2.37 MiB) Downloaded 454 times

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

Re: "Different" ZX81's

Post by Lardo Boffin »

And it appears the kludge fix bus is in town -

IMG_6437.JPG
(2.46 MiB) Downloaded 424 times

That's number three now!

It's working but needs a new keyboard or someone with smaller fingers than mine. I tried the trimming back the ribbon but the smaller connector is so stiff it keeps bending. I tried another keyboard that is not attached to a case and that went in fine as I could get a better grip on it.

This is up for 'adoption' on viewtopic.php?f=8&t=2482 if anyone is interested.
Last edited by Lardo Boffin on Mon Jul 31, 2017 1:11 pm, edited 1 time in total.
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
gammaray
Posts: 590
Joined: Sun Apr 17, 2016 2:44 am
Location: Texas

Re: "Different" ZX81's

Post by gammaray »

Now the obvious question is will you make a custom unit that has a switch for choosing the power supply circuit...?

sirmorris wrote: Fri Jun 16, 2017 11:44 pm
Lardo Boffin wrote: Fri Jun 16, 2017 7:15 pmIf I do get round to making a zeddy laptop

1) If 9 volts were used would that be ok?
2) What changes would be required to the ZXPand otherwise?
A1: Yes.
A2: I build 5V 'spands by leaving off the regulator and jumpering the 5v line on the edge connector to the regulator output pad. For a pre-existing 'spand you can either remove the regulator (quite hard) or cut its tracks/jumper the 5v.

A decent 5v supply should be able to supply both computer and xpansion.
5-TS1000,UK ZX81<-Sheelagh, US ZX81, 2-TS1500/KDLX , 3-TS2040 printer, 2-TS2020 cassette decks, ZXPAND+AY, ZeddyNET, ZXBlast, UDG, ZX8CCB, AERCO, BUILDS/REPAIRS ZX Spectrum, ZX80 Minstrel, ZXMAX48 v1 v2, 2-TS-2068, ROM, 16kRAM
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