I'm trying to test the video section of the Apple 1 Replica but it doesn't seem to work. I was able to compile the source code after some minor modifications because the original code won't compile. I have the video section on a protoboard and I'm not seeing output (Q pin5) on the 74HC74 frequency divider. I noticed that it takes the clock signal directly from the XTAL of the Atmega8, and this signal is about 100mVp which is way too weak for the 74HC74 to work. Also this signal is close to a sine wave and I think the 74HC74 should have a square wave as a clock. Datasheet says VIH is about 2V, which means that it will never work. The circuit I'm testing is the one on page 235 of the "Apple 1 Replica Creation" book.
I'll appreciate any comments.