Simple Oscilloscope

During the 1960s Mullard produced some technical documents detailing the construction of 3 oscilloscopes:

A Pupil's Oscilloscope

A Student's Oscilloscope

The Serviceman's Oscilloscope

The pupil's oscilloscope was a simple design using a DH3-91 1 inch cathode ray tube and a single ECL80 valve.  The triode section of the valve was used as a vertical amplifier and the pentode section as the timebase the timebase had no facility for syncing it to the vertical signal.  The supply was from a 12V DC source running a simple inverter.  The design was kept low cost and minimal to enable schools and colleges to build a number of these for use by groups of pupils.

The student's oscilloscope was a more complex design using a DG7-31 cathode ray tube and 6 other valves.  The oscilloscope had a y bandwidth of only 20kHz was of modular construction and was intended for use by secondary schools and technical colleges.  The unit was mains powered and used a transformer that would be expensive to source today.

The serviceman's oscilloscope used a DG7-32 cathode ray tube and 5 other valves, this unit was intended to be used by a service technician and had a Y bandwidth of 2.5MHz

The simple oscilloscope described here will have a performance approaching that of the serviceman's oscilloscope but with a complexity only slightly greater than that of the pupil's oscilloscope. 

The design is based on a Cossor 1039 oscilloscope, manual with schematic available here: 

http://www.thevalvepage.com/servdata/testeq/cossor.htm

The design shown here uses a DG7-6 tube, this tube can be driven assymetrically.  This enables the Xplates to be driven directly from the timebase valve without the need for a phase inverter.

The scope uses only 2 valves plus CRT, both valves are EF91.  The Y bandwidth is about 1.5MHz with the amplifier gain switch at minimum gain.  I will upload the full circuit diagram with component values in the near future.

 

Figure 1. Timebase and Y ampilfier

 

Figure 2. Complete Oscilloscope

 

Figure 3. Oscilloscope bottom view

 

Figure 4. Oscilloscope top view

 

Figure 5. Oscilloscope front view