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 50ms/div
• no x10 magnifier, direct access to 5ns/div speed
• timebase B always runs after timebase A and has no separate trigger
• timebase mode A+B actually display A intensified by B alternating with B
• 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	50ms to 5ns
Trigger modes	norm, auto, single sweep
Trigger sources	internal, external, external/10, line

Pictures

• 

  Front

• 

  Threequarter view

• 

  Left side internal

• 

  Left side detail

• 

  Timebase A PCB

• 

  Tunnel diode in Timebase A trigger

• 

  Right side internal

• 

  Right side detail

• 

  Timebase B PCB

• 

  Output amplifier PCB

• 

  Closeup of PCB construction

• 

  Factory-added tape to insulate capacitors from side panel

• 

  Cam-operated microswitch to select variable time/div