Sinclair ZX80 / ZX81 / Z88 Forums

Hi folks
Got a zx81. It works but video display into lcd TV with antenna in with manual uhf tuning is very streaky. Background is white and text black, so but corrupted with horizontal streaks.
What can I do?
Could rf modulator be bad?
Cheers
D

Does your TV have a fine tuning control?

The modulators used in 1980s computers are analogue with a simple oscillator, so they do not produce an output at the exact TV channel frequency that modern LCD TVs expect. So see if using the fine tuning control helps.

Also note that because the inside of the case of a ZX81 warms up, this will also cause the modulator to warm up, this affects the output frequency, so it may drift off-tune.

Mark

Yes it does have a fine tune... I tried that for quite a while. There is no place where it looks good enough to read the screen clear enough. Attached image is as good as it gets. Anything else to try?

Can you solder?
Does your TV have a composite video input on a phono / RCA connector?

Mark

Welcome Chalkie666,
I would also go for a composite video mod. I am afraid its only in german. Bit maybe still helpful.

There are a number of options for adding a composite video output.

If you want a built board where you only need to solder some wires, have a look at this one from PokeMon.

If you are happy to build your own circuit, search this forum

Mark

Also, may I suggest that you try 1024MAK/Dessony strip board video buffer amplifier?
http://www.sinclairzxworld.com/viewtopi ... fer#p25270
Mark designed the circuit. I made it simpler by using a Veroboard/stripboard.

Thank you very much in advance.

Cheers,
Dessony