Sinclair ZX80 / ZX81 / Z88 Forums

From Digikey-Canada
https://www.digikey.ca/en/products/deta ... 15n/738684

There's a method to paint high relief surfaces using a coin wrapped in a cloth.

is there any signal on pin 1 (shift/load)? if so check for signals on the outputs of the shift register.
Also check if the bridge for selecting normal/inverse video is ok.

cursor is made by inverting the video signal cat xor gate (ic20) commanded by D7.
Characters are made by shift register, IC9. Check if this IC is receiving both clock and load signals.

It should be possible to connect a Master System Paddle using a cable adapter for playing breakout style games. I have wrote some asm code for Zeddy and for Speccy

https://github.com/Danjovic/ZX/tree/master/paddle

Adapter should route pin 7 (+5V) on Kempston interface to pin 5 on SMS controller.

You can add backporch capacity with some spare gates and have a video signal with correct output impedance and amblitude with mere 3 resistors (link1) (link2)

1024MAK wrote: ↑Mon Jul 29, 2019 5:45 pm Have you studied the ZX80 schematic?

Mark

Yes, I have studied the zx80 and some zx81 clones, and all of 'em use a capacitor in series thus forming a high pass filter but then again a low pass filter would make more sense.

Hi folks. I am routing a custom version of ZX97 board and after reading some material about tape loading I got concerned about what should I use as a front end on the input buffer pin (ear). I haven't found answers on the plenty articles and posts I have researched, not even on the ROM lisiting avai...

Thanks people for sharing this amazing project. I have routed a couple of boards for this project, being one for use with a box by Hammond, reference 1455C801 and AAA cells but can also be used standalone as it has mounting holes. I have used stereo jacks for input/output as such parts are very easy...

If you use a 74LS688 or 74HCT688 MAGNITUDE/IDENTITY COMPARATOR you can test for /WR low, /MREQ low plus 7 address lines (say A9 to A15) all in one chip. Data sheet (PDF) here Mark Good point. I have some of these here, although they are a bit hard to find in local stores (at least harder than the '...