Updated (and hopefully, finished) the SB-630 update.
All Tubes and the Plate-Filament transformer were removed (and saved, for future tube projects). The clock was given to a local collector who prefers to keep his Heathkits original. The functionality replaced – and enhanced – by adding a Real-Time Clock (RTC) chip, a WWVB receiver and Arduino code to interpret the 1950′s era clock signal.
The WWVB receiver reads each ‘pulse’ of the signal and interrupts the Arduino (INT1) to add the ‘tick’ to the buffer. Once the whole signal is recieved, it can be interpreted as a date and time. The RTC pulses (INT0) each second in order to drive the display clock.
In addition, an LM35 sensor provides the current room temperature.
Original WWVB decode source from http://duinolab.blogspot.com/2009/06/arduino-cmmr-6p-60-almost-accurate.html (Capt Tagon) and all others who’ve improved this code. Website seems abandoned, but the source code is good. My alteration is to remove the timer interrupt (1000 times a second) which operates the 1-second tick and replace it with the square wave output (SQWE) signal from the RTC chip, a Maxim DS1307.