ZX81CCP

[PokeMon]

So from today there is a new (following) model of the ZX81CCB which is now called ZX8-CCB.
It is in fine white color, double sided with silk print, a little bit bigger with 0.8 x 1.0 x 0.1 inches (20 x 25 x 3 mm) and still fit in the modulator case.
You will find technical information here:
viewtopic.php?f=6&t=840&start=90

And the available boards as usual on sellmyretro.com here:
http://www.sellmyretro.com/user/profile/PokeMon


And this is how it looks like now:

[PokeMon]

Additional information for all people using professionell broadcast monitors rather than (older) TVs. I got mine last week and the picture is brilliant but I found out that there is a small black stripe in the left side of the screen which is even a bit noisy in the first (visible) pixel column. So broadcast monitors show a bit more from the video signal as normal TVs do which have a generous overscan of up to 10%. So about 10% of the visible picture is cut on the TVs or the picture is zoomed a little bit.

The reason is of the non standard syncpulse, which is too wide with approx. 6.0 us while allowed is only 4.7us (+/- 0.2us) from PAL TV standard based on ITU/EBU. This is the length d in the picture. The ZX8-CCB simply adds the backporch after the sync pulse with a backporch width of about 5.5 us, given a all-in-all black period of about 11.5us (b in the picture) while the standard set the length to 10.5us.

pal.jpg (25.52 KiB) Viewed 9049 times

So to solve this, you may replace R4 on ZX8-CCB with a SMD 7k5 value (0805 size) instead of the 10k value which shortens the backporch to about 4us which gives a combined sync/backporch with length of about 10us and avoids a unclean line visible on a broadcast monitor. Just in case someone uses it ...

IMG_7881kk.JPG (237.97 KiB) Viewed 9049 times

If anybody needs additional ZX8-CCB - they are modified with this resistor as changed value from now.

[PokeMon]

I made a picture how the ZX8-CCB could be mounted and connected in an original ZX80 (using the wonderful work of Grant Searle as a screenshot background ).
For people want to use it with a ZX80.
I am sure it needs new adjustment from the factory setting which is described in the "manual".

ZX80_Original_ZX8CCB.jpg (91.5 KiB) Viewed 9024 times

[PokeMon]

The ZX8-CCB (latest version in white colour) is available back - these have been sold out for about 2 weeks I think due to new pcb production.

[BIG-Trev]

Hi. I can't seem to get your board to work properly and I'm wondering if I have a faulty ULA chip. I've removed the rf modulator and placed the board in its casing with the output wires going to the tv socket and the supply and input wire coming from the board. I still get a distorted K on the screen but the inverse function works ok.
Cheers Trev.

[PokeMon]

I don't think that the ULA is bad when you get a synced picture with black and white pixels shown as chars.
Did you use the invert jumper on the board (J7) to inverse the picture ?

[BIG-Trev]

Yes I did use the jumper. I've wired a switch to it so I can change it without opening the case. The zx81 had a different composite board in it when I got it but it was crudely made so I removed it and put yours in.(it too had a distorted K) I've wired the input to the UK2 pad next to the modulator which I believe goes straight to pin 16 on the ULA chip, is this correct?
Thanks Trev

[BIG-Trev]

I have to apologise as it was my monitor that was playing up. I was using a Kaga green screen and now I'm using my Apple green screen and the picture is clear but missing pixels which I'm guessing is the ULA being a 1981 version. Time to look for a replacement.
Thanks for your help.
Trev.

[Moggy]

In my experience Karl's wonderful little device works with all three types of ULA, so would have thought that your ULA is just faulty in itself and not because it is an early type.

[PokeMon]

Yes I did use the jumper. I've wired a switch to it so I can change it without opening the case. The zx81 had a different composite board in it when I got it but it was crudely made so I removed it and put yours in.(it too had a distorted K) I've wired the input to the UK2 pad next to the modulator which I believe goes straight to pin 16 on the ULA chip, is this correct?
Thanks Trev

The UK-2 pad is correct at an issue 3 board.
Hmm - you said you got a valid picture with pixels when you used your old monitor.
What should be different to the newer monitor and what do you think where the pixel may have been gone when nothing changed internally ?
Can you recheck with your other monitor ?
I am a bit confused now ...