Here are some links to repair tips and reference material.
460 Series / 475 Repair Tips (video)
The 4051 had three firmware releases during its production. This July 7, 1976 document details the corrections and the serial number breaks for the various releases.
4051 Firmware Releases
We don't know the source or reason for this document which describes the more popular transistors used at Tektronix.
Everything About Transistors
This undated document describes the phase-in of earthtone colors instead of the traditional Tek blue.
New Color Scheme
- 7L12 Spectrum Analyzer Plug-in
- Casting a Replacement Knob
- 468 +5V Storage Supply
- 468 Vertical repair
- 465B and 468 Oscilloscope Horizontal Sweep Problems
- 400 Series Oscilloscope Vertical Attenuator Testing
- 400-series High Voltage Multiplier and CRT Replacement
- 475A / DMM44 Repair
- 4B53A Dual Time Base Repair
- Capacitance Keyboard Repair