123

The Tektronix 123 is a miniature preamplifier introduced in 1955.

Tektronix 123
miniature preamplifier Tek 123 front Produced from 1955 to (?) Manuals Tektronix 123 Instruction Sheet (All manuals in PDF format unless noted otherwise)

Manuals – Specifications – Links – Pictures

It is intended to be used as an audio-frequency AC preamplifier for other instruments such as oscilloscopes.

Key Specifications

Bandwidth	3 Hz to 25 kHz
Voltage gain	×100 (40 dB)
Noise	≤7.5 μV_RMS, input-referred
Max. input	0.1 V_p-p
Input impedance	10 MΩ
Output impedance	31 kΩ
Power	One 1.345 V mercury battery (RM3R) and one miniature 30 V battery (413); 100 hours runtime

Prices

50$ in 1960 (~$500 in 2023 dollars)

Internals

The 123 uses two CK512AX pentodes for amplification and is powered by batteries.

Although the 123 is an AC amplifier, the output is taken directly from the plate of one of the tubes, without an output coupling (DC block) capacitor. So the output signal rides on about 15 volts of DC.

Pictures

Description in 1958 Catalog
Front panel
Schematic
Parts list
Left side panel – circuit diagram
Right side panel – parts list
External view
internal view

Components

Some Parts Used in the 123

Part	Part Number(s)	Class	Description	Used in
CK512AX	154-0114-00	Vacuum Tube (Pentode)	flat-press subminiature pentode	123