Bodge of the week: replacing a naked piezo buzzer

  • March 20, 2018
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HerpDerp Mucking About With Things Sodding soldering The Diary of Lupin Pooter
A never-used, presumably functional timer and its innards at top and my bodged-and-working timer below.
Two specimens of the same model of timer. Top: an as-yet-unused timer, opened up to show its innards. Bottom: my good-enough-for-now five-minute fix: soldering an SMD pieze buzzer to two of the leads on a transistor inductor.

A few days ago, a dual-clock kitchen timer we’ve had for years stopped making much noise when its alarm went off. When its sliding high-low-off volume switch was set to high, a muffled version of the original beep was just barely audible.

At the time that we bought it, we liked the timer enough to get spares. They’d stayed in their boxes thus far and I didn’t want to junk this one if a quick fix was feasible. Opening the case tonight, I was surprised to find that the white ceramic coating on the piezo disc was nearly gone, except for the region immediately around the solder joint on that part of the disc. As to how that happened, I have no clue.

The aim was to get the sound back as quickly and with as little expenditure of effort as possible, so I didn’t bust out a multimeter and try to trace the circuit. That’s why I’m calling this repair a bodge.

Some sifting through parts drawers here didn’t turn up any bare piezo buzzer discs, but I did find some KLJ-9032-3627 SMD Magnetic Buzzers. Using temporary leads to connect one of them to the terminals on the PCB where the piezo had been attached and running through five-second countdowns on the timer didn’t yield any sound, but connecting them directly to two of the leads on a through-hole transistor inductor gave a satisfactory result. With a bit of soldering, I made the connections permanent, closed the timer’s case back up, and put it back into service.