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7B92: Difference between revisions
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The 7B92 uses a discrete trigger circuit containing [[152-0177-02]] [[tunnel diodes]]. Up to serial number B069999, the 7B92A used a trigger circuit with [[155-0061-00]] amplifiers and [[152-0177-02]] tunnel diodes. After that, the 7B92A used a [[155-0061-00]] trigger amplifier followed by a [[155-0150-00]] trigger detector. | The 7B92 uses a discrete trigger circuit containing [[152-0177-02]] [[tunnel diodes]]. Up to serial number B069999, the 7B92A used a trigger circuit with [[155-0061-00]] amplifiers and [[152-0177-02]] tunnel diodes. After that, the 7B92A used a [[155-0061-00]] trigger amplifier followed by a [[155-0150-00]] trigger detector. | ||
[https://vintagetek.org/years-at-tektronix-hofer/ According to Bruce Hofer], early 7B92 models exhibited sweep anomalies especially near the start of the sweep, and after trying to fix these he convinced management that a redesign was needed. This resulted in [[ | [https://vintagetek.org/years-at-tektronix-hofer/ According to Bruce Hofer], early 7B92 models exhibited sweep anomalies especially near the start of the sweep, and after trying to fix these he convinced management that a redesign was needed. This resulted in [[Patent US 4009399A]], the [[7B92A]] update, and the [[067-0657-00]] calibration fixture. | ||
The 7B92A uses one other custom IC, the [[155-0049-00|155-0049-xx]] sweep control circuit. The internal jumper for mainframe selection (7800/7900/7100 vs. slower) actually increases the minimum holdoff time on the slower mainframe selection by adding a 214 pF capacitor (C307 for 7B92, C835 for 7B92A) to pin 8 of the sweep control IC [[155-0049-00|155-0049-xx]] in parallel to the existing capacitors. This increases the minimum pulse width of the holdoff signal on [[7000_Series_plug-in_interface|pin B4]] so that the sweep logic of slower mainframes can handle it properly. The effect of this jumper is only noticeable for sweep speeds of 20 μs/Div and faster, since there the smallest shunt capacitance is used on pin 8, and the holdoff time is minimal. | The 7B92A uses one other custom IC, the [[155-0049-00|155-0049-xx]] sweep control circuit. The internal jumper for mainframe selection (7800/7900/7100 vs. slower) actually increases the minimum holdoff time on the slower mainframe selection by adding a 214 pF capacitor (C307 for 7B92, C835 for 7B92A) to pin 8 of the sweep control IC [[155-0049-00|155-0049-xx]] in parallel to the existing capacitors. This increases the minimum pulse width of the holdoff signal on [[7000_Series_plug-in_interface|pin B4]] so that the sweep logic of slower mainframes can handle it properly. The effect of this jumper is only noticeable for sweep speeds of 20 μs/Div and faster, since there the smallest shunt capacitance is used on pin 8, and the holdoff time is minimal. | ||