Found Zx81 working

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owen2471

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I'm looking for a good condition working zx81. Just need the computer, nothing else. Needs to have a good picture through rf lead. And needs to stay on when keys are pressed. To many on the other bay are listed has untested.
 
There is an inherent issue with ZX81s and LCD tvs. If its an issue 1 Zeddy, then its likely to have a ULA that provides no 'back porch' signal, which, translated to English usually means that the display becomes very dark.

Later versions of the '81 (v3 onwards) had a better ULA which gives a better picture on modern TVs.

The problem is that someone could quite innocently sell you an '81 as tested with pictures showing it on a CRT - but when you get it, it looks very poor on your LCD - its always going to be a gamble.

There is another issue too... When the ULA starts to get warm, the signal starts to drift, so you have to keep retuning the tv - old CRTs seem to have some 'aft' setting that logged onto this drift and auto-corrected it. LCDs (or all the ones I've used) sdo no such thing.

You could go the ZX Vid route - available from RWAP - that replaces the modulator, adds the required backporch signal and gives you composite, or you could buy a ULA2 (but then you haven't got a true ZX81).

Now, with all this in mind, I can sell you a ZX81, but wont be able to guarantee it will work on *your* tv, but could show you piccys of it on mine. If you are interested, drop me a PM and we can discuss a price or a possible exchange or r3tr0 items ;)
 
Here's some pics....

All rubbers underneath are in place. Program typed in as shown...
 

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Payment of £25 + £5 p&p received for ZX81 (y) This will be despatched tomorrow by recorded delivery. THANKS
 
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