565
The Tektronix Type 565 is a dual-beam scope that takes two 2-series or 3-series vertical plug-ins.
It was introduced in 1963.
A rackmount version, the RM565, was also produced. Aside from being dual-beam, the 565 is unusual among the other 560-series scopes in the fact that it (the mainframe) has built-in trigger, sweep, and horizontal amplifier circuits.
Specifications
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Circuits
The 565 uses the T5650 CRT.
Vertical Signal Path
As is usual for 560-series scopes, the vertical deflection plates of the CRT are driven directly, differentially, by pins 17 and 21 of the vertical plug-in. The left plug-in bay is for the lower beam and the right plug-in bay is for the upper beam.
A 0.7—3 pF trimmer capacitor is connected immediately behind each of the plug-in connectors, and allows for the mainframe to be calibrated so that plug-ins can be interchanged without requiring the high-frequency compensation of the system to be readjusted. The capacitance seen by the plug-in driving the scope should be 14.3 pF for either beam.
There is no trigger pickoff in the vertical signal path of the 565. That function is performed by the plug-ins.
Trigger and Sweep
The triggering signal comes from pin 11 on the plug-ins, is amplified by a 12AT7-based cathode follower, and sent to "TRIGGER" switches. From there, the trigger signal is sent through a 6DJ8-based differential amplifier and then is discriminated by a 6DJ8-based Schmitt trigger.
The sweep delay can be adjusted over a range from 10 microseconds to 50 seconds.
The 565 is also unusual in that it employs a tunnel diode in the trace intensification circuit. The tunnel diode forms as a bistable multivibrator: kick it one way and it turns on and stays on, kick it the other way and it turns off and stays off.
Calibrator
The internal calibrator produces a 1 kHz square wave with amplitude selectable in decade steps from 1 mV to 100 V. It is an astable multivibrator formed by one half of a 12AT7 and a 6AU6. The other half of the 12AT7 serves as the output cathode follower for the calibrator.
Comparison with the 556
The 565 appears similar to the 556, but is different in many ways. The 556 uses tunnel diodes for triggering, while the 565 uses tubes. The 556 uses letter-series and 1-series plug-ins while the 565 uses 560-series plug-ins. Moreover, the bandwidth of the 556 is specified as 50 MHz, while the bandwidth of the 565 is specified as 10 MHz. Subjectively, the trace of the 565 is very sharp, sharper than the trace of the 556.
Pictures
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Front from RM565
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Open 565
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RM565 with P7 CRT
