I have the above-mentioned radar detector (Radio Shack cat. no. 22-1621), but the buzzer doesn't work. When the detector is turned on, it does a self-test, during which the buzzer is supposed to sound. The sound it produces is very faint (I have to put it up to my ear to hear it). The volume control does have an effect on how loud it is. Could this be a bad buzzer? Its in-circuit resistance is ~41 ohms, and the voltage across it is -0.004 V with the volume turned up all the way, and -0.001-2 when turned down. I also found a blown up resistor which goes from power to the + side of the buzzer. The resistor is dropping all of the supply voltage, so there must be a short on the other side (either the buzzer or the low-side driver). But since the buzzer does produce sound when it's supposed to (shuts off after the self test), I'm assuming the driver is ok and the buzzer is the problem. Am I on the right track? I can provide pictures if needed.
PS: I don't have a schematic for it. The info I provided was from tracing the circuit on the board.
PS: I don't have a schematic for it. The info I provided was from tracing the circuit on the board.
I found the problem. It was a shorted cap that was pulling the buzzer power to ground. Replaced the cap and the fried resistor, and now it works.
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