These are photos of an oscilloscope that I bought on 19 September 1980.
More information about the model is available here.
Mainframe
The mainframe has a dual beam CRT and
two vertical amplifiers with a bandwidth of about 33 MHz, along with delay lines and the
high voltage system. It has 4 slots for plug-ins: the upper two are for time bases, the
lower two for vertical amplifiers. This instrument came with two “work horse” CA vertical
amplifier plug-ins. It was last calibrated on 16 May 1979, a little
over a year before I bought it:
There are two delay lines, one for each beam, around the top and back of each side. The
perforated plates in the images above are for the adjustments. Here they are from an angle:
The CA plug-in provides 2 vertical input channels with a bandwidth of about 20 MHz. There
are two of them in the instrument, at the bottom. One each feeds the upper and the lower
beam, so in this configuration the instrument can display 4 beams.
The 22A time-base plug-in was the secondary time base. Line the 21A, it had calibrated
sweep ranges from 100 ns/cm to 5 seconds/cm. The big difference was that the sweep could be
triggered based on the operation of the 21A, as the last image shows.