View Full Version : Found Zx81 working

2nd June 2013, 12:49
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.

2nd June 2013, 13:42
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 ;)

2nd June 2013, 13:56
Pm on the way.

2nd June 2013, 14:45
Here's some pics....

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

2nd June 2013, 15:50
Payment of 25 + 5 p&p received for ZX81 :thumbsup: This will be despatched tomorrow by recorded delivery. THANKS

2nd June 2013, 16:06
Many thanks. A smooth transaction.