🇧🇾 Квант (Quantum): Part 2 (No video output) [TCE #0457]
22I've started doing some work on this Belarusian Sinclair ZX Spectrum clone.
The joystick looks relatively sturdy and well made (compared to other examples I've come across) so thought it'd be worth spending some time on. I've resprayed the top case blue so it's looking nice. I'm thinking of replacing the fire button mechanics to improve the tactile feel.
I added an additional power socket to the Квант main case - a 2.5mm DC socket so I can power it from a USB charger or my bench supply.
At 5V it currently draws about 500mA.
The RGBS output uses the same pinout as its compatriot, the Сантака 002 (Santaka) ... of course, I couldn't find that cable so made up a new one. Made the effort to make it nice.
The pinout is:
Pin 1 = green
Pin 2 = ground
Pin 3 = sync/video
Pin 4 = red
Pin 5 = blue
Absolutely no signal is output, no black screen nor any multi-coloured jumble of garbage ... so the computer isn't processing anything at all?
So some investigation is required - what I did quickly tonight:
[1] I can see activity on most address lines
[2] Data lines look noisy
[3] !HALT pin of Z80 is low all the time
The machine uses a pair of Western 27C64 8KByte EPROMs (with custom version of the Speccy firmware), otherwise it appears to be all Soviet-era logic (no ULA, yay!) and an East German Z80 clone (U880D).
Thanks again to @LastofAvari:
Lots of excellent information (in Russian), including documentation & circuit fixes:
https://zxbyte.ru/inter.htm