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The Tektronix Type 1A1 plug-in for the 500-series scopes has two channels and a −3 dB point of 50 MHz at 50 mV/Div, 28 MHz at 5 mV/Div, and 2 Hz to 15 MHz at 500 μV/Div when channels 1 and 2 are cascaded.

There were three distinct versions of 1A1.

  • The first version, from 1964 to 1966, has a Nuvistor front-end, and rotary input switches that were concentric with the BNC jacks. The knobs to invert the input channels are concentric with the vertical position knobs.
  • The second version, from 1966 to ??? has fluted round V/cm knobs, and lever switches. The channel inversion control is an organ-style pull-push knob. The nuvistors are mounted under a thermal cover on a sub-chassis with rubber stand-offs.
  • The third model, from ??? until the end has four-sided V/cm knobs and a FET front-end.

Type 1A1 uses the "ALT SWEEP SLAVE PULSE" signal that is sent by scopes on pin 7 of the plug-in connector. In a Type 547 mainframe, this signal allows channel 1 to be displayed using the "A" timebase and channel 2 using the "B" timebase. This is useful, for example, to view the IF and AF of a radio receiver at the same time. Even after the front-end transitioned from Nuvistors to FETs, the output amplifier continued to use Nuvistors.

Type 1A1 has an External Trigger output for mainframes prior to the 547 that don't support plug-in triggering, and supplies the trigger system on pins 4/5 of the mainframe interface. It also has a ×10 amplified output from channel 1 that can be cascaded into the channel 2 input for 500 μV/Div sensitivity at reduced bandwidth (15 MHz).

Types 1A1 and 1A2 were introduced together in 1964, the former for high-end use, the latter as an upgrade/replacement for Type CA. Both remained available until the 500-series scope line was discontinued.

The 1A1 is not a perfect superset of the 1A2; it supplies external trigger from channel 1 only.

The 1A1 may have evolved from the Type J, which never went into production.


Bandwidth 50 MHz @ 50 mV/Div and up (in fast mainframes), 28 MHz @ 5 mV/Div, 15 MHz with cascaded channels (~0.5 mV/Div)
Rise time 7 ns @ 50 mV/Div and up (in fast mainframes), 13 ns @ 5 mV/Div, 24 ns with cascaded channels (~0.5 mV/Div)
Deflection 5 mV/Div to 20 V/Div, 1−2−5
Max. input 600 V DC + peak AC
Input impedance 1 MΩ // 15 pF
Modes Ch 1, Ch 2, ALT, CHOP, ADD