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Tektronix 506
20 MHz scope
506 with 9A1 and 3B1

Produced from 1964 to (?)

Manuals – Specifications – Links – Pictures

The Tektronix Type 506 is an oscilloscope with bandwidth above 20 MHz that uses 560-series horizontal plug-ins but special high-speed vertical plug-ins, the 9A1, and 9A2.

Like the scopes in the 560 Series, the 506 mainframe contains neither vertical nor horizontal amplifiers; the plug-ins directly drive the CRT deflection plates.


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The 506 uses the T5033-31-1 CRT, which has P31 phosphor. It uses no post-deflection acceleration, total accelerating voltage is 3.5 kV.


The CRT circuit uses two 5642 high-voltage rectifier tubes, one for the CRT cathode voltage and one for the intensification voltage, which is applied to a second grid in the CRT.

The calibrator signal is produced by shaping mains frequency into a square wave. It is not just a simple clipping circuit. To speed up the edges, positive feedback is used. A cross-connected triode and pentode form a schmitt trigger. The input of the shaping circuit is the cathode of the triode and the output is the cathode of the pentode, which drives a voltage divider whose tap is selected by the front panel calibrator rotary switch.

The power supply is fairly typical of Tektronix scopes of the period. An OG3 tube establishes a −82 V reference voltage in the −100 V power supply section. The −100 V supply is then used as the reference voltage for the other power supply sections. Output tubes are used for all of the regulated supply voltages except the −12.2 V supply, which uses a 2N1529 germanium PNP transistor.