Readouit flashes continuously ...

Power supply C554, a 100uF 16V electrolytic capacitor seems to be under rated for ripple current and dries up. It does not vent or deform. Replacing this capacitor with a 2200uF 25V electrolytic capacitor completely fixes the problem. If you cannot find a part that is physically small enough, you can connect some insulated wire leads to the capacitor and tack solder them to the place where C554 mounts. Locate the part in the space close to where the power transformer resides, but make sure it will still fit when you close the case before you commit to a location. Secure it with a drop of hot melt glue. This fix restores proper operation to the clock - even without a battery installed. Note: another symptom of this problem is that the clock works with a fresh battery for a day or two, then resets to the "Zone 1" display, finally then blinking "Zone 1" continuously as the battery dies. The problem is NOT the "watchdog" or any other part of the circuitry. It is the lack of filtering of VCC causing the micro to go through resets when the supply droops.