I took apart my old oscilloscope to have a look and clean it up. I had inherited this ‘scope from my father-in-law, and it’s served me quite well for years.

Specifications

Telequipment is a registered trademark of Tektronix, U.K. I found the D66 User and Service Manual online. The manual is dated 1977.

• 25 MHz
• All solid state
• Dual trace
• 8 x 10 cm CRT
• Sum, alternate, chop channel displays
• X – Y display

The manual is incredibly detailed and is comprised of six sections: Specifications, Operating Instructions, Circuit Descriptions (with full explanation of the design), Maintenance and Calibration, Component List (every single part), and Circuit Diagrams (complete schematics).

Build

This instrument is solidly built. All calibration trimmers are accessible, if you would care to calibrate it (requires another oscilloscope, signal generators, etc.). I disassembled a few parts with the aim of measuring the ESR on the old electrolytic capacitors and to look for pots I could clean. The design is modular, with three main and several smaller circuit boards. All the transistors are in sockets! Why? I was hoping to remove the board with all of the large electrolytics to test ESR and possibly re-cap, but unfortunately although some of the connections have wires with disconnect pins, a lot of the wiring under the board is directly soldered in. The ESR (Effective Series Resistance) that I was able to check was a bit high, not good, but not terrible either. So I gave up on the re-cap idea.

I was able to spray some CRC into three of the pots and the two switches for DC/AC probe coupling, but many of the pots were inaccessible.

Photos