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I'm a beginner in electronics. I'm trying to follow the below schematic for building an astable 555 circuit. Based on the resistance set on the trimmer potentiometer, the speaker should make sounds of different pitches.

Astable 555 multivibrator from the book "Make: Electronics" (3rd ed.)

However, it never makes any sound. After several days of troubleshooting this, I have tested all components (wires, speaker, capacitors, resistors, 555 timer), and they all work. When measuring voltage, it's present on the "right" side of the circuit (e.g. when measuring voltage drop on the lower of the 10k resistors, it's ~9.2V; though there is 0V across the "vertical" 10K resistor).

I also swapped the speaker with a working LED, and it never lit up, irrespective of the resistance set on the 500K potentiometer.

How can I troubleshoot this further? Here's my actual circuit, where I re-checked each connection around 5 times already, and even rebuilt the circuit twice:

Pic 1 Pic 2 Pic 3

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Your rendering has a red wire (orange jumper in reality) connecting ground to the /RESET input (pin 4), which will keep the 555 from operating. It needs to go to the supply voltage (pin 8).

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  • \$\begingroup\$ Indeed, this was the reason, thank you! I will raise this with the book's author, as it's clearly an oversight. \$\endgroup\$
    – slazien
    May 25, 2023 at 1:45

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