From Barbouri’s Electronics Projects blog:
After finishing the IceTube clock version 1.31 build for myself, I was ready to work on the board design for some IceTube clocks as gifts. I could have used the existing V 1.31 boards, but I wanted to use an up to date design that incorporated all the hardware improvements over the past 10 years while still staying with a thru-hole design.
This updated design is based on jarchie’s (John Archie) xmas-icetube clock revision D board. He had incorporated most of the hardware features that I wanted for my new batch of clocks, along with a vastly improved firmware update.
One of the most important hardware improvements for me was the ability to properly drive the IV-18 tube to specifications (providing more even display illumination and preventing cathode poisoning). Some other features of the design are the inclusion of an one wire temperature sensor near the oscillator crystal to provide highly accurate temperature compensation of the crystal frequency, reset pull-up resistor, micro-controller power decoupling capacitor, GPS connection pads, along with an improved board layout while still maintaining physical compatibility with Ver. 1.X board switches and connectors.