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Tektronix 7D14
525 MHz frequency counter
7D14 front view

Compatible with 7000-series scopes

Produced from 1971 to 1980

Manuals – Specifications – Links – Pictures

The Tektronix 7D14 is a 525 MHz frequency counter plug-in for 7000 series mainframes.

It uses the mainframe's readout system to display an eight-digit count on the CRT. Modes include frequency, frequency ratio and events count using manual or external gate.

When installed in a horizontal compartment, it can count the trigger pickoff from a vertical amplifier unit. This allows simultaneous viewing and counting of a signal in four-bay mainframes.

In a vertical compartment, the trigger signal (i.e. the "shaped" input) can be displayed as the module's Y output.

Key Specifications

Frequency 525 MHz (5 MHz bandwidth limiting switch available)
Sensitivity 100 mV to 10 V
Input Impedance 50 Ω or 1 MΩ // 20 pF on external input, 1.5 Div internal when set to "Trig Source"
Gate time 1 ms to 10 s
Display time 0.1 s to 5 s or infinite
  • Gate monitor output / Ext Gate input (BSM)
  • 1 MHz reference monitor output / Ext Ref input (BSM)


An input section using relays selects the counter signal from the internal trigger path or external input, and activates 50 Ω termination and/or attenuators.

A differential FET buffer + bipolar amplifier stage drives a counter gate that uses a 10 mA tunnel diode as the switching element.

The first counter decade is implemented as a divide-by-2 ECL flip-flop (U329) followed by a five-stage ring counter made with discrete transistor pairs (note circular layout) and some logic to BCD-encode the count result.

In early 7D14 units (board 388-1825-00), U329 was a Tek made IC, 155-0046-00, which was not used in other instruments. From SN B050000 on, a standard ECL part (156-0377-00) was used on a a redesigned high-frequency counter board (670-0993-01).

The following seven counter stages are conventional TTL decade ripple counters (N8292A).

The counter outputs are multiplexed onto a common 4-bit bus using open-collector NAND gates under control of the mainframe's readout system. The multiplexed digit value feeds a D/A converter (Tek 155-0038-01) that in turn drives the analog row and column returns to the readout system. A separate blanking logic eliminates leading zeroes and displays a ">" sign in the leftmost column if the counter overflows.



Year 1973 1976 1980
Price $1,400 $1,550 $2,075
In 2021 Dollars $8,600 $7,450 $6,900


Custom ICs used in the 7D14

Page Model Part nos Description Designers Used in
155-0038-01 155-0038-01 155-0038-00 155-0038-01 5-bit current source D/A converter Mike Metcalf 7A42 7D13 7D14 7M13 T4005
155-0046-00 155-0046-00 high-speed divider Luis Navarro 7D14