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Tektronix 7D14
525 MHz frequency counter
7D14 front view

Compatible with 7000-series scopes

Produced from 1970 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.


Documents Referencing 7D14

Document Class Title Authors Year Links
Tekscope 1971 V3 N1 Jan 1971.pdf Article Digital Counter and Multimeter 1971
Tekscope 1971 V3 N5 Sep 1971.pdf Article The 7D14 Counts Current to Minimize Circuit Loading Emory Harry 1971
Tekscope 1972 V4 N2 Mar 1972.pdf Article A Review of Basic Counter Principles Ray Herzog 1972
7000 Series Digital Plug-In Applications.pdf Application Note 7000 Series Digital Plug-In Applications 1977


Year 1973 1976 1980
Catalog Price $1,400 $1,550 $2,075
In 2023 Dollars $9,700 $8,400 $7,700



Some Parts Used in the 7D14

Part Part Number(s) Class Description Used in
155-0038-01 155-0038-00 155-0038-01 Monolithic integrated circuit 5-bit current source D/A converter 7A42 7D13 7D14 7M13 T4005
155-0046-00 155-0046-00 Monolithic integrated circuit high-speed divider 7D14
SMTD994 152-0177-01 Discrete component 10 mA, 2 pF tunnel diode 067-0587-01 067-0580-00 3T5 3T6 485 5S14N 7D14 7T11 7T11A S-53