A month ago I noticed Tynemouth Minstrel 3 ZX81 clone.
Details at:
http://blog.tynemouthsoftware.co.uk/201 ... r-kit.html
https://www.tindie.com/products/tynemou ... puter-kit/
It seems to be the perfect basis for tinkering around on this retro style device as all of the parts can be replaced easily if broken and it would fit into the original ZX81 case.
I ordered one of this batch of PCBs and brought it to life yesterday.
Great work! Thanks to Tynemouth,
What I changed from the build instruction:
Power supply:
I am using an external 12V switching power supply.
Also using a switching regulator to generate 5V (It will never save the amount of energy to be economic but will save some CO2)
As I noticed that there are external power supplies with different pin assignments I added an diode to protect the circuit.
Rom:
I did some rewiring at the socket to connect the original ROM out of my 1982 device as I botched up the old board.
So I own a clone with a licensed operating system.
Ram:
I replaced the 32k by a 128k chip using a 32 pin socket but wired A15 and A16 to VCC for now. (Planning to enable 56k or 64k in future)
Type of 74 chips:
To keep compatibility with LS and reduce power consumption I choose HCT chips for all of the 74xx
Other:
Based on my current stock I choose BAT48 instead of the 1N4148.
As I didn't found a vendor for 6.5MHz crystal I took a 6.55MHz one.
And then TATA!! alive on first try


Device is up and running but all of the characters are shifted to the right for some pixels.
Surprised Max