EEVblog #1208 - Circuit Analysis & Debugging

[EEVblog]

Fundamentals Friday
Dave answers a beginner forum question of why their 74HC390 based breadboard counter circuit does not work properly.
Let's get up to our armpits in datasheets and troubleshooting.
A two sentence forum response turned into a step-by-step 27min video investigation involving rise and fall times, setup and hold times, metatability, optocouplers, bypassing, open collectors, and connector traps for young players.

[Raj]

Quick googling resulted in 74HC4024-Q100, ripple counter with schmitt 'cp' input....7bit though

[mancausoft]

About the noise of the audio, if you have it you should disable NFC before start shooting.
 I have the same problem and same type of noise, and it's seems was the NFC.

In some case you can see the NFC signal on monitor/tv:
https://youtu.be/Xf5-yam1wKc

I spent a lot of time to found the cause of this noise, because was present even on  airplane mode.