I Built a 27V Circuit to Fix This $3 Gadget I revived a cheap scribble pad by swapping its fried board for a tiny PCB that boosts a coin cell to 27 V—enough to cleanly reset the bistable LCD. It’s a Joule Thief with Zener regulation and twin 220 µH inductors (mounted in opposite orientations), pulling ~17 mA during charge and ~7 mA while regulating. It’s coin-cell friendly, works great, and just needs a bit of case surgery for a perfect fit. 07 November 2025