Sinclair ZX80 / ZX81 Forums

ZX8-CCB is temporarily sold out but planned to be come back in a few weeks.

The ZX81 keyboards with tactile switches as replacement for membranes is back now after 6 weeks sold out. There is only the completed/assembled version available but with lower price (same now as previous kit price). So assembly kits and pcb only are no more available as all boards have been assembl...

Cool !

Not sure where you measure but can be a ground problem at the end. What is the signal when you take it directly with GND and VID on your small board (as close as possible) ? I wouldn't take the signal from the modulator or feed it through as this can give more problems. Where do you get your signal ...

Maybe possible to post a better resolution picture here with the normal screen (how it should be) and what is different with ZX8-CCB.
I can not see much from these pics, sorry. Just a white line in between.

Wow ! good work !

Yes I like these "little logic" gate series. The LVC (low voltage cmos) are fast and powerful. No need for transistors.

By the way - I changed R5 to 150R long time ago, didn't update the schematics.
R6 stays still 390R.
Together with 75R load gives about 1Vpp Video at the output.
No need for any decoupling capacitors or short circuit protection.

maybe i use a sot-23 dual inverter / buffer that will do same job but save on pcb space. Yes - that's the best. Get your digital video and sync to these and mix together after. Take this sot 23-6 device 74LVC1G14 for example. https://assets.nexperia.com/documents/data-sheet/74LVC2G14.pdf Maybe you ...

Be aware how you realize the transistor amp. If this is just an emitter follower, than the shit comes out of the CPLD already. Anything you do at the 5V or second video power supply rail will have no effect.