ZX81 Power Supply

sabre128

I have a ZX81 with the original 0.7A power supply. I know that this has trouble running many add-ons and was seeking advice on a suitable replacement at 1.2A (I think). Is there an off-the-shelf solution? There is a Maplin's near me, but I knew you lot would be a lot more helpful!:smile:
Many thanks.

1024MAK

sabre128 wrote: »

I have a ZX81 with the original 0.7A power supply. I know that this has trouble running many add-ons and was seeking advice on a suitable replacement at 1.2A (I think). Is there an off-the-shelf solution? There is a Maplin's near me, but I knew you lot would be a lot more helpful!:smile:
Many thanks.

Any unregulated DC power unit with an output voltage of between 8V and 9.5V or a regulated DC supply with an output voltage of between 8V and 10V will do. Just ensure that the tip on the 3.5mm jack plug is the positive output connection. If you have a multimeter use this to confirm ;).

Unregulated types have a higher output when the output is not connected to a load (12 to 14V for "9V" rated units).

The exact current rating is less important as long as it is equal or greater than the required current. Sinclair specified 1.2A so that it could operate a ZX81, ZX Printer and 16k RAM pack.

What were you intending using with your ZX81?

Mark

Spirantho

I use Spectrum power supplies (1.4A) through a home made adapter - just get a standard jack-to-jack lead, snip off the end, and solder on a barrel connector socket. Job's a good 'un.

Or you could use the ZX81 psu that comes with the ZX Printer.

sabre128

Thanks both. I am intending to use a Chroma 81 with a ZXPand and was told that the 0.7A power supply that I have wasn't up for it. I therefore need a bit more juice.
I do have a spectrum power supply, is it possible to use an adapter on this without permanently changing it?

balford

Yes it is, Spirantho's solution is one I've implemented also:



Just ensure that the polarity is correct :)

B

1024MAK

sabre128 wrote: »

Thanks both. I am intending to use a Chroma 81 with a ZXPand and was told that the 0.7A power supply that I have wasn't up for it. I therefore need a bit more juice.
I do have a spectrum power supply, is it possible to use an adaptor on this without permanently changing it?

What balford said! :p.

As long as the polarity is correct, you will not damage a ZX81 when using such an adaptor cable and a ZX Spectrum "1400" 9V 1.4A power supply unit (*).

As long as there are no short circuits, you will not not damage a ZX Spectrum "1400" 9V 1.4A power supply unit when using a ZX81, a Chroma 81 and a ZXPand together.

If you have a spare ZX Spectrum "1400" 9V 1.4A power supply unit that you don't mind modifying, you could just cut the existing 2.1mm power plug off, then solder on a 3.5mm jack plug. Or if you can't do this yourself, ask someone who can do this for you.

As an example of a power supply you could buy, here is one suitable type. Similar units are available from many other shops and stores.

Mark

PS other "9V" ZX Spectrum PSU are also suitable, but would be a bit over specified for your intended use :p

sabre128

Many thanks. You have given me a few options. A great deal more helpful than Maplin's would have been I'm sure!!