[Dekatron]

A search for "ct160 grid volts" here on the forum shows a few different ways of how to replace the grid volts potentiometer in the CT160. Mike Phelan has a nice solution where you modify a 25K potentiometer which means that you can use the original dial.

Forum member "einovaan" made a design similar to the AVO Mk IV with a range switch and a linear potentiometer and I myself used a 10-turn potentiometer, both of these two solutions make use of a new dial and in my case I used a counting dial.

One old, and original, grid volts potentiometer that I had in a CT160 I owned previously even had the text "Log." stamped into the metal case, I have seen similar photos on the Internet with this text too.