1Start by the shorter components
First components to be soldered on the board should be the ones that are shorter in height.
Start by the resitors.
Then add the diodes
2Then add the IC sockets
And solder the P2 Jacks
3Next solder the capacitors
First the ceramic and polyester capacitors
Followed by the electrolytics
4Add some headers
Add some pin headers, specially the Power Supply header
5Plug the PSU and perform some tests
Plug the PSU to the board and test for the correct voltage (5V) at all IC sockets.
6Test the clock
Solder the Crystal and insert U4
Power the board and check for 6.5MHz signal at pin 3 of U4
7Test the frequency Divider
The frequency divider is It is one of the few pieces of ZX81 video generating circuit that run standalone (mostly).
Insert U5, U6, U7, U23 and place a jumper wire from pin 2 of U23 to ground.
Then check for:
3.25MHz at pin 1 of U6
A Negative going pulse of 4.6us (Hsync) at pin 6 of U4 . The HSync frequency shall tick at 15.7Hz.