Search found 14 matches

by Danjovic
Sat Mar 20, 2021 12:38 pm
Forum: Hardware
Topic: ZX81 Letters
Replies: 15
Views: 8252

Re: ZX81 Letters

There's a method to paint high relief surfaces using a coin wrapped in a cloth.
by Danjovic
Tue Jan 12, 2021 9:38 pm
Forum: Hardware
Topic: ZX80 machine that shows a cursor but no text FIXED! :)
Replies: 18
Views: 4264

Re: ZX80 machine that shows a cursor but no text

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.
by Danjovic
Sat Jan 09, 2021 6:02 am
Forum: Hardware
Topic: ZX80 machine that shows a cursor but no text FIXED! :)
Replies: 18
Views: 4264

Re: ZX80 machine that shows a cursor but no text

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.
by Danjovic
Mon Nov 09, 2020 8:01 pm
Forum: Hardware
Topic: Using a Kempston Joystick Interface with a ZX81
Replies: 8
Views: 5328

Re: Using a Kempston Joystick Interface with a ZX81

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.
by Danjovic
Wed Aug 07, 2019 12:28 am
Forum: Development
Topic: Jupiter ACE Kit /sorry half off-topic! :)/
Replies: 18
Views: 79653

Re: Jupiter ACE Kit /sorry half off-topic! :)/

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) ;)
Image
by Danjovic
Tue Jul 30, 2019 6:11 am
Forum: Hardware
Topic: Tape Loading
Replies: 4
Views: 2231

Re: Tape Loading

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.
by Danjovic
Mon Jul 29, 2019 4:13 pm
Forum: Hardware
Topic: Tape Loading
Replies: 4
Views: 2231

Tape Loading

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...
by Danjovic
Tue Aug 21, 2018 3:46 am
Forum: Hardware
Topic: Improving Timex/Sinclair Tape Loading
Replies: 164
Views: 86083

Re: Improving Timex/Sinclair Tape Loading

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...
by Danjovic
Sun May 24, 2015 1:11 am
Forum: Development
Topic: Kolour
Replies: 14
Views: 6026

Re: Kolour

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 '...