7S14

7S14 is a 1GHz dual-trace delayed sweep sampler plug-in. It is a complete sampling system unlike, for example, the 7S12, which requires a separate timing plug-in to provide triggering and sampling pulse generation. The 7S14 contains two samplers, trigger and sweep circuitry, and circuitry to interface it with the 7000-series mainframe in which it operates. The mainframe provides the 7S14 with power. The 7S14 sends the mainframe horizontal, vertical and readout signals.

There are two 1.35V mercury button cells, BT1 and BT2, in the sampler circuit. They act as floating bias sources, so if a 7S14 stops working it may be not defective, just dead batteries. First check the voltage on the cells. When the mercury cells die, you can replace them with other (less toxic) methods of bias voltage generation. Two obvious solutions are photovoltaic cells or modern batteries. The issue has been discussed extensively on the Yahoo TekScopes forum, so search the archives there for more information. Notably, Ed Breya posted detailed notes on the 7S14 bias cell issue.

The 7S14 has an integrated delay measurement function.

• Risetime = 350 ps (This means 1 GHz bandwidth)
• Vertical deflection 2mV/DIV to 0.5V/DIV in 1,2,5 sequence
• Time base deflection factor 100 µs/DIV to 100 ps/DIV in 1,2,5 sequence
• delayed timebase
• 50 ohms input
• allowed input voltage range is 5Vpk

The 7S14 has two triggering modes: triggered and HF-sync. In triggered mode, the signal passes through two stages of MC1672 ECL logic gate, and then into the 155-0109 trigger chip. In HF-sync mode, the 7S14 uses a BD4 back diode (0.1mA, 3pF), and inductor, and a 152-0177-00 tunnel diode (10mA, 4pF) to form an oscillator that oscillates somewhere between 16.5MHz and 25MHz.

The sampler used by the 7S14 is a two-diode design. Each of the two input channels has its own sampler.

Manuals

• Tektronix 7S14 Service Manual (PDF)
• Tektronix 7S14 Instruction Manual (PDF)

Pictures

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  7S14 front

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  Sampler schematic

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  Trigger schematic