What is it?

[Chiltern]

This is not my field at all, this item came with a clearance lot from our local auction.

Recognise it? There is no name on it, one of the chips inside marked 'Sinclair', looks almost home made.

Alan

[BassoonBloke]

Hi Alan,

It looks like a re-housed ZX81, they did this to replace the original keyboard as they weren't great.
There is a lot of info on the web about the board inside and it's connections. Get it powered up and feed it's output to an old (?) analogue TV and see if it works.

Cheers,
Alan.

[Brian R Pateman]

It looks like Sinclair ZX81 in a home made case using standard keys to replace the membrane keys fitted as standard.

I built the power supply and a cassette recorder into mine as well.

Many of the plethora of kit and component suppliers did kits of parts. The standard keyboard was pretty poor.

[julie_m]

It's a Sinclair ZX81 that has been installed into an after-market case with a proper keyboard.

Quite a nicely-done one, too! Note that the edge connector and power / tape / TV jacks were on adjacent edges of the ZX81 motherboard, so something must have been extended here to bring them into a straight line (internal RAM pack, maybe?)

Any chance of some pictures of the interior?

[Chiltern]

I think that this era just passed me by, many thanks for your help.

here are some pictures of the interior.

does it have any value or is it simply a curiosity?
Nice piece of insulation board for the base, might have a use for that!

Alan

[julie_m]

The green daughter board is a RAM expansion, probably 16K.

Value-wise, it's worth whatever anyone is prepared to pay for it. Does it work (white screen with an inverse K in the lower left hand corner) if you plug it into a TV set tuned to channel 36?

[SiriusHardware]

Originally Posted by Alanomt

This is not my field at all, this item came with a clearance lot from our local auction.

Recognise it? There is no name on it, one of the chips inside marked 'Sinclair', looks almost home made.

Alan

As stated by others, this is a re-housed Sinclair ZX81 computer.

I can tell you one other thing, the case/keyboard was almost certainly made by a third-party producer of Sinclair add-ons called 'DKtronics'.

My 48K Sinclair Spectrum has spent most of its life in an almost identical DKtronics keyboard / enclosure.

The primary difference between mine and yours is the key legends - yours don't have the giveaway 'colour' keywords of the Spectrum version. The key legends are the weak point of the design, unfortunately - when you bought the keyboard/housing the key tops were all blank and you had to legend all the keys yourself by applying a transparent sticky-backed transfer to each key.

Like any other type of adhesive tape the sticky stuff went gooey and liquid after a few years and the transfers started to slide around all over the place. A pity, as the keyswitches themselves were excellent and it was a huge improvement over the original Sinclar dead-flesh rubber keyboard. Another important factor was all the space available inside, providing much needed air circulation / ventilation.

Just recently, I've reassembled the Spectrum back into its original 'historic' form, but I still have the DKtronics keyboard.

[SiriusHardware]

Originally Posted by Alanomt

I think that this era just passed me by, many thanks for your help.

here are some pictures of the interior.

does it have any value or is it simply a curiosity?
Nice piece of insulation board for the base, might have a use for that!

Alan

Honestly, don't break it up.

It's actually more rare, more interesting and more usable than a standard ZX81, especially with that internally installed RAM expansion. The 'proper' external ones used with the standard housing were a menace, always wobbling loose.

Also, this example (squinting at your pictures) is one of the rare late ones with the 2C210 ULA - the one which outputs a properly formed video signal, complete with 'back porch'. The 2C184 used in most (earlier) ZX81s has a video signal defect which prevents the ZX81 from working very well with modern TVs.

So see if it works!

[Happy Listener]

Did it come with the power supply..?

[Chiltern]

No power supply, the 4 sockets on the back are marked up, TV, ear, mic, and 9vDc.

I will not be going any further with it, as I put at the start of the thread, this is not my field. At least I now have some idea 'what it is' and I thank you all for your information.

If anyone has an interest, send a PM

Alan

[julie_m]

You need a supply of 9 volts, 1.2 amps (if you wish to use a ZX printer) or 0.7 amps (for just the computer and memory expansion). Needs to end in a 3.5 mm. mono jack plug, and (unusually for '80s kit) the tip should be positive. The heatsink on IC5, the 7805 regulator is the limiting factor here.