507
The Tektronix Type 507 was designed for the power industry for surge testing. It was introduced in 1959. The scope was intended to operate in an environment of strong electromagnetic fields. It does not take plug-ins. The power supply is external, like the 517, 551, and 555.
The vertical signal path of the 507 does not contain amplifiers. It has a 5 nanosecond risetime. The input impedance of the 507 is 72 ohms. The maximum sensitivity is deliberately low: 50V/cm. The input attenuator is very unusual for Tek scopes. It is a switch with ten positions in "% of signal", where each step is 10%. The deflection signal is permanently AC-coupled and, unusually, the DC blocking capacitor is after the input attenuator.
The 507 has 20kV of post-deflection acceleration, produced by four 1X2 tubes. The lower-voltage power supplies, located in the external box, are all tube except for selenium rectifiers for some of the lower voltages.