Dear Bo, BRAVO to have found this classic 1980 machine.
Suggest you get the printed service manual for the serial number range and follow the mechanical disassemble proceedure
For swith contacts NEVER USE WD40, dangerous to plastic parts ans WILL NOT clean a contract.
WD40 is a petroulum distillate TO REMOVE WATER, not a cleaner or lube.
USE ONLY isopropyl alcohol and ELECTRONICS GRADE CONTROL CLEANER / LUBE !!!
Some are afficanados of Deoxit, but we never use it.
For the knobs, very typical, deteriorated plastic, breaks at the set screws.
Impossible to glue to gather after they break.
Suggest you post the photos and TEK part numbers of all the broken knobs here, in BUY..SELL..WANT and other Tektronix fouums also EEVBLOG in Wanted.
Finally contact to Tektronix Vintage Museum in USA, Beaverton Oregon who MAY have these very rare knobs.
Bon chance
Jon
Jean-Paul