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 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.