Я4С-91

The Я4С-91 is a dual timebase plug-in for Soviet 7000-series clones. It is roughly analogous to the Tek 7B53A. It features a 3И306К tunnel diode in the timebase A trigger circuit.

Significant differences to the 7B53A include:

• slowest sweep speed 50 ms/div
• no ×10 magnifier, direct access to 5 ns/div speed
• timebase B always runs after timebase A and has no separate trigger
• delay time is set by a single-turn pot with a reduction drive, and it is not calibrated
• only timebase B has variable time/div

The external trigger connector is a СР50-73 type. The plugin contains a number of integrated circuits of type 130ЛА3, which is a TTL quad 2-input NAND gate in a surface-mount package, like a 7400.

The example in the photos is labelled in German. A version labelled in Russian also exists.

Key Specifications

Time/div	50 ms to 5 ns
Trigger modes	norm, auto, single sweep
Trigger sources	internal, external, external/10, line

Pictures

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  Front

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  Three-quarter view

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  Left side internal

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  Left side detail

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  Timebase A PCB

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  Tunnel diode in Timebase A trigger

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  Right side internal

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  Right side detail

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  Timebase B PCB

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  Output amplifier PCB

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  Closeup of PCB construction

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  Factory-added tape to insulate capacitors from side panel

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  Cam-operated microswitch to select variable time/div

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  Interconnect board (Timebase B and output amplifier removed)