"Different" ZX81's

[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?

[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.jpg (260.2 KiB) Viewed 6279 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.jpg (46.65 KiB) Viewed 6279 times

Mark

[sirmorris]

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

Not important, but noteworthy.

[Lardo Boffin]

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

[Lardo Boffin]

Yes, the wires look like they are connected to the correct points on the ZX81 circuit board....
Mark

Thanks Mark!

[sirmorris]

If 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]

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

[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

[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.

[gammaray]

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

If 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.