🇧🇾 Квант (Quantum): Part 5 (Clock Flip Flop Replaced) [TCE #0468]
23Today I thought I'd try injecting a clock-ish signal in with a higher, known voltage, one that should be within the Z80's requirement.
However the flip flop (К555ТМ2) that generates the 7MHz and 3.5MHz clocks from the 14MHz original was still outputting a signal around 4V, when its Vcc input voltage was 4.9V.
The Z80 expects the high level of the clock signal to be at least Vcc - 0.6V, so around 4.3V at least.
I de-soldered the chip and installed an IC socket and a 74HCT74 (no 74LS74 on hand).
And the voltage level improved ... too much! Now it seems that we're above the Z80's Vcc+0.3V max.
I'll order some 74LS74 and try again.
But ... making progress?
From Part 1:
Let's have a look at this Belarusian Sinclair ZX Spectrum clone called the КВАНТ (KVANT) or Quant(um) in English.
It's labelled "КВАНТ МИКРО ЗВМ" where ЗВМ is an abbreviation for "Электронная Вычислительная Машина" ... Electronic Calculating Machine ... so it's a "Quantum Micro Computer".
Lots of excellent information (in Russian), including documentation & circuit fixes:
https://zxbyte.ru/inter.htm