The Tektronix Type H is a single-channel plug-in for 500-series scopes. It provides two inputs and has a switch to select between them. The rise time of the plug-in is 20 ns, bandwidth is 15 MHz. The sensitivity ranges from 5 mV/cm to 20 V/cm. A design compromise, Type H is not as fast as Type B, but it is DC-coupled on all ranges.
Later Type H models use a turret attenuator. Type H with S/N less than 10,000 have ordinary attenuators.
The input is switched via a Frequency compensated attenuator network which is controlled by the Vols/CM Switch.
Input is then coupled to the paraphase amplifier or phase inverter made up of two 12AU6 pentode tubes - V3854 and 4854. This stage converts the input signal to a differential push-pull output. Output of this stage is thenn passed to the first cathode follower, made with a pair of 12AT7 dual triode tubes V3863A and V3863B. The output from this cathode follower is thenn passed to the main amplifier made with a pair of 12AU6 pentodes, V3874 and V4874. The final output to the scope chassis is driven via final cathode follower with a pair of 12AT7 dual triode tubes, 3893A and 3893B, which drives pin 1 and 3 of the connector to drive the vertical amplifier inside the chassis.
Heater for the tubes are derived from +75VDC heater supply available at pin 15 of the connector. This is to avoid any interference/hum from the regular AC heater supply at 60Hz.