The 511, Tektronix first oscilloscope, had limited vertical sensitivity. It has two stages of gain which could be switched in which provided 250 mV, 2.5V, or 25V per cm of vertical deflection. To achieve greater vertical sensitivity the 121 preamplifier was developed provide up to 100X gain from 5 Hz to 12 MHz, preserving the bandwidth of the oscilloscope. The 121 first appeared in the 1950 catalog for a price of $265.00. The 121 preamplifier last appeared in the 1959 catalog.
The serial number on our instrument indicates it was the 1343rd instrument made.
Similar to the 511, the Type 121 shows methodical construction. This is a view of the top of the instrument. you can see a large cutout on the top chassis where below is a "floating" chassis mounted on rubber shock absorbers for the sensitive preamplifier components.
The right side of the 121 shows the heavy transformers and power supply components on the bottom. You can see the "floating" chassis just below the top chassis.
Our 121 preamplifier is displayed with our Type 101 and 511 oscilloscope.