7D14

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
Features	Gate monitor output / Ext Gate input (BSM) 1 MHz reference monitor output / Ext Ref input (BSM)

Internals

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 decade is implemented as a divide-by-2 ECL flip-flop followed by a 5-stage ring counter made with discrete transistor pairs (note circular layout) and some logic to BCD-encode the count result.

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.

Links

• http://www.barrytech.com/tektronix/tek7000/tek7d14.html
• 7D14 page @ amplifier.cd

Pictures

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  7D14 front panel. The unit pictured was able to count up to 640 MHz on the external input and 532 MHz on the trigger path (7A19 in 7904).

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  7D14 left side

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  7D14 right side

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  7D14 detail - input amplifier. Own photo.

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  7D14 detail - counter gate

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  7D14 detail - 525 MHz divide-by-2 stage

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  7D14 detail - divide-by-5 discrete ring counter stage

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  7D14 screen picture - 500 MHz signal counted on trigger path (7A19 amplifier, 7B92A time base in a 7904 mainframe)

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