Apple-1 Clock

[kalinchuk]

I'm trying to debug an issue with the Apple-1 and when I scope the clock signal (coming out of the D12 7404 pin 6) I get a sine wave instead of a square wave. Is that normal? Should I be expecting a square wave? Additionally, it appears as though the high is 2.5v and the low is 1.2v. There might be a voltage difference because of the oscilloscope connection but shouldn't it be dropping under 0.8v for LOW?



Thanks in advance

 

[george]

I doubt the 172 MHz frequency is normal to Apple1. But the sine wave is normal at that high frequency for 7404.

 

[kalinchuk]

I changed out the 7404 for another one and the frequency changed to 14.3 MHz. The voltages are also much closer now (between 0 and 3 volts).

 

[kalinchuk]

After changing the 7404, the clock signal looks like the image below. No longer a clean sine wave. Is that normal?