The new knob is a hair small, esthetically, but completely functional. I drilled the center hole, installed the new V/div knob and then added the thru rod and inner knob for the Series Resistance. They work great. To wrap this up, I want to add a nut to hold the V/div control a bit more firmly in place, but I can perform any device testing as this sits.
|Replacement V/div knob behind the Series Resistance one|
Originally, the Peak Wattage lever would turn the inner scale, but I can just refer to the scale and set up a spreadsheet that lists the settings for each of the four wattage peaks.
|Resistance setting guide for .5 Watt peak|
|Rotary scale and teeth that engage with the Peak Wattage lever|
NUT TO HOLD CONTROL ASSEMBLY IN PLACE
The nut on the control assembly was a cylindrical shaft around which the scale rotated It was much too deep to allow my replacement knob to work. I tried to match the threads to bolts at local hardware stores, to determine the thread type for the nut I would buy. It was closest to Metric 10 or 3/8" Imperial, but the threads are finer than those in the stores. M10-1.0 was too coarse, as was 3/8-24.
I decided that it must be M10-0.75 although I couldn't find any of them at the big box stores or local hardware shops. Based on the likelihood that this is the proper size, I ordered some nuts online that were that size; should be here within a week.