The Tektronix Type 4S3 is a 1 GHz dual-trace vertical sampling plug-in for the 661 oscilloscope. It uses two P6038 sampling probes.

Tektronix 4S3
1 GHz dual-trace sampling plugin
4S3

Compatible with 661

Produced from 1963 to (?)

Manuals
(All manuals in PDF format unless noted otherwise)

The probes contain sampling gates but not amplifiers. The front-end amplifier is in the 4S3 and is composed of a 7308 tube (premium 6DJ8) with its two triodes connected in a common-cathode cascode topology.

Pictures