You are more then welcome here and I am sure the others would have some questions about your Pentagon’s clone.
Hehe, thanks a lot!
Regarding a questions in this thread, i will try to answer for a few:
1) For more correct colors / brightness some people reported that they have used 680 Ohm resistors instead of 3k9 (R10, R12, R14) , and 3k + diode instead of 18k ones (R9, R11, R13). I guess this because of Pentagon timings 48Hz instead of 50Hz in Harlequin 48k.
2) For the oldest NMOS Z80 CPUs, the CLK pull-up resistor 2k2 should be replaced with 680 Ohm. Then it will work like a charm
3) And yes, you can use any series of the 74xx logic (even mix them), like 74LS, 74ALS, 74HC, 74HCT, 74ACT, etc. The only sensitive part is a generator, best results can be obtained with 74F04.
4) Regarding PAL coder, it's seems very sensitive to the 4.43MHz crystal internal impedance, so, in case of no colors at all, you can solder a 4M3 resistor in parallel of the crystal.
5) Regarding memory extension to 1024kB, yes, it's a bit destructive operation, you should crack some routes and wire them a different way, there is a manual in the git repository. One day i would like to release a new revision (C, probably) of the karabas-128, but not now
There are some ideas to use a bigger CPLD, like in karabas-nano (EPM3256 or even EPM7512), so then i can fit more features inside this board, like DivMMC, kempston joy, CF card, additional video modes, UART (for the wifi module), may be, etc
Please be patient
