Sinclair ZX80 / ZX81 / Z88 Forums

Here proposal for putting the board inside the ZX81 case, can be fixed with doublesided tape:





and proposal for a video out with a 3.5mm audio or video connector



Tomorrow I will publish a nice video which shows the difference in the picture signal and the functionality of the board.

Excellent work

Mark

Made some nice video to demonstrate.
In the beginning my camera had some problem synchronising during flickering screen - but that's true, no fake.
After 1 minute it's not more flickering so much.
This flickery can not be seen in reality that way - only a little bit caused from only 25Hz frame rate (shown 2 x 25 half pictures).
With inverted mode flickering can be eliminated fully, don't know about 100Hz TVs (don't have ).

Have fun.

http://www.youtube.com/watch?v=TKNu3kavPl0

This is really good stuff, now that CRT's are getting harder to come by solutions for good display on LCD are a must for all ZX81's

Thanks for sharing i may well implement this solution on my latest creation as it too has some switching noise in the video signal.

Regards Andy

No problem, good luck.
If you want to invert your picture I would propose to use two 86 gates (XOR), instead of the 74LVC1G386.
This was hard to get, had 20 EUR shipment and mimimum 100 pieces.
Even Farnell has it not on stock.

And use the LVL logic gates instead of TTL.
They are really cool, spare power consumption, very fast and powerful output.
I think I banned TTL from my workbench for future.

Well... Looks like you've sold out. Thankfully I got in there in time.

But are there any plans to do another batch? I needed two really.

Well that was fast.

Now added additional 8 items.
I think this will be all in the first step.
Could do another charge of boards when finished.

This time I want definetely have one for my own.
Last time some private "out of system orders" forced me to finally sell my own board to someone.

Here is the link of all items (including new listings):
http://www.sellmyretro.com/user/profile/PokeMon

Funny, every board has it's own individual touch.
Due to capacitor tolerances the stripes during LOAD look a bit different with every board on the same Zeddy.
But there are more tolerances in conjunction with your ZX81 model (resonator tolerances as well).

So it's maybe not possible to accidently confuse your personal Zeddy on an exhibition like in Mahlerts.
Everybody can easily see if it's him or hers.

Hahaha. That's super cool - signature loading screens.

No luck today - I wasn't in L.A.

Sorry I have to inform about a small delay in shipping the boards.
Had some problems when opening a new bag with 1nF capacitors.
Could find them only with +/- 5% tolerance.
The resistors have +/- 1% tolerance.

The sync generator (hsync) is too slow with the new capacitors. I think something about 15 kHz, not 15.625.
Just between 2 or 3 %.
So I have to order some other resistor values to vary it on the board.
Think new shipment couldn't be done before monday.

Sorry Rink and others.
By the way, the first five or six boards did run without any problems.
Seems that I had a very exact 1nF capacitor in my first bag.

I wonder if the rumours about the bad quality of the resonators are true - maybe only rumours.