• Leaky Ni-Cd clock battery

The Ni-Cd battery may be leaking, risking damage to PCB layers & nearby components. Promptly remove the battery & clean corrosion/alkaline salts from the board. Use white vinegar to dissolve salts, but exercise caution as vinegar can corrode exposed metals. A thorough examination & repair may be needed. Replace battery with guide: https://github.com/wiretap-retro/Not-A-Varta

If you wish to use a non-rechargeable coin cell (e.g. CR2032) to replace the old clock battery, disconnect the diode directly next to the battery. This will stop the board from attempting to charge it.