The NC620 Nixie Clock Board from Cathode Corner

The NC620 clock board uses round end-view tubes for that retro look.

This clock is based on the Scope Clock switching power supply and CPU,
and uses the same computer program structure. The digits are multiplexed,
which results in a very simple circuit. Note that there are only 2 ICs
(68HC705 CPU and 74141 cathode driver) and a dozen transistors in the clock.

The power supply is a switching type, capable of running
on 100-240VAC 50-60Hz, so it works worldwide.

This clock board can use the old style 13-pin round end-view tubes.
Common type numbers are 6844A, B-5092, B-5032 and ZM1020.
New Old Stock ZM1020 tubes are available from Cathode Corner.

You can chop off the seconds digits with a hacksaw if you hate seconds,
but most folks enjoy watching the numbers dance around in the tubes.

Two pairs of wires from the red connector at the top of the board
go to two pushbuttons to set the time. The red button selects which
digit is being set, and the black button advances that digit.

The clock board comes with pre-crimped wire leads and power cord, but no

A jumper allows selection of 12-hour or 24-hour time. The leading
zero is blanked in 12-hour mode, but not in 24-hour mode.

There is no date or alarm function. This is a mantle clock.


Dimensions: 8.8" wide x 1.8" tall x 3.0" deep including ZM1020 tubes

AC Power: 90-250VAC 50-60 Hz, 2 Watts


The NC620A instruction manual PDF file, complete with schematic and panel diagram, is here.

The NC620 is all gone. Sorry.

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Last updated 7/25/2010