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565: Difference between revisions
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and then is discriminated by a [[6DJ8]]-based Schmitt trigger. | and then is discriminated by a [[6DJ8]]-based Schmitt trigger. | ||
The 565 is also unusual in that it employs a [[tunnel diodes|tunnel diode]] in the trace intensification circuit. The tunnel diode forms | The 565 is also unusual in that it employs a [[tunnel diodes|tunnel diode]] (D845, a [[TD4]], which is equivalent to the [[1N3718]]) in the trace intensification circuit. | ||
it turns off and stays off. | The tunnel diode forms 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. The tunnel diode is DC-coupled to the base-emitter junction of Q843, | |||
which is a 2N404 germanium PNP transistor. Because the tunnel diode and transistor are DC-coupled, the transistor needs | |||
to be germanium. This is one of the rare cases when a failed germanium transistor cannot be replaced with a silicon part. | |||
Contrast this with the timebase A trigger of the [[585|585A]], which uses a tunnel diode AC-coupled to a transistor, which | |||
makes the forward voltage of the transistor's base-emitter junction irrelevant. | |||
=== Calibrator === | === Calibrator === | ||