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== Triggering modes == | == Triggering modes == | ||
A 661 can be triggered in at least four distinct modes: | A 661 can be triggered in at least four distinct modes: | ||
* The 4S1 uses a trigger pickoff transformer to produce the internal trigger signal that can trigger the timing unit. | * The 4S1 uses a trigger pickoff transformer to produce the internal trigger signal that can trigger the timing unit. The 4S1 is the only 661 sampling unit that produces an internal trigger signal. | ||
* An external trigger signal can be fed to the timing unit via its front panel. | * An external trigger signal can be fed to the timing unit via its front panel. | ||
* The timing unit can be operated in in free-running mode and the resulting pulse signal can be the stimulus for the device under test. This mode is similar to a TDR. | * The timing unit can be operated in in free-running mode and the resulting pulse signal can be the stimulus for the device under test. This mode is similar to a TDR. | ||
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=== Power Supply === | === Power Supply === | ||
The power supply is typical of Tektronix scopes of early 1960s. | The power supply is typical of Tektronix scopes of early 1960s. | ||
The other supply voltages use the +300 V supply as their reference. | An [[OG3]] tube is used as a voltage reference for the +300 V supply. | ||
The other supply voltages use the +300 V supply as their reference. | |||
The +19 V and -19 V supplies use BJT-based regulators. | |||
The other regulators are tube-based. | The other regulators are tube-based. | ||
The 661 has a 137°F/58 °C [[thermal cutoff]]. | The 661 has a 137°F/58 °C [[thermal cutoff]]. | ||
In practice, it doesn't run hot. | |||
=== Indicator === | === Indicator === | ||
The indicator is a conventional X-Y indicator. | The indicator is a conventional X-Y indicator. | ||
The total CRT accelerating voltage is 3 kV and the vertical and horizontal amplifiers are | |||
relatively mild differential amplifiers made of [[6DJ8]] tubes and [[OC170]] germanium bipolar junction transistors. | relatively mild differential amplifiers made of [[6DJ8]] tubes and [[OC170]] germanium bipolar junction transistors. | ||
The vertical and horizontal amplifiers have feedback loops around them that determine their gain. | The vertical and horizontal amplifiers have feedback loops around them that determine their gain. | ||
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=== Calibrator === | === Calibrator === | ||
The amplitude/time calibrator is a Colpitts oscillator that uses a [[7119]] tube. | The amplitude/time calibrator is a Colpitts oscillator that uses a [[7119]] tube. | ||
from 100 kHz to 100 MHz and amplitudes from 1 mV to 1 V. The output is 50 Ω [[GR-874 connector]]. | It produces clippped sine waves at frequencies | ||
The signal from the calibration generator is available on the front panel and is also sent to the timing generator through the multi-pin plug-in connector. | from 100 kHz to 100 MHz and amplitudes from 1 mV to 1 V. | ||
The output is 50 Ω [[GR-874 connector]]. | |||
The signal from the calibration generator is available on the front panel | |||
and is also sent to the timing generator through the multi-pin plug-in connector. | |||
This allows the timing plug-ins to select "CAL" as a trigger source. | This allows the timing plug-ins to select "CAL" as a trigger source. | ||
In this mode, the calibration generator can be used as the stimulus for the device under test. | In this mode, the calibration generator can be used as the stimulus for the device under test. | ||
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with a risetime of about 150 ps and a pulse width of about 400 ns. | with a risetime of about 150 ps and a pulse width of about 400 ns. | ||
The output is a 50 Ω [[GR-874 connector]]. | The output is a 50 Ω [[GR-874 connector]]. | ||
When a timing unit (e.g., a 5T1) triggers, it sends a pulse through pin 10 of the J4 interconnect to the delayed pulse generator, which regenerates the pulse. | When a timing unit (e.g., a 5T1) triggers, it sends a pulse through pin 10 of the J4 interconnect | ||
to the delayed pulse generator, which regenerates the pulse. | |||
There are three versions of the 661 delayed pulse generator (serial numbers 101 through 2829, 2830 through 3459, 3460 and up). | There are three versions of the 661 delayed pulse generator (serial numbers 101 through 2829, 2830 through 3459, 3460 and up). | ||
All three versions use a 50 mA, 6 pF germanium tunnel diode to generate the actual output pulse. | All three versions use a 50 mA, 6 pF germanium tunnel diode to generate the actual output pulse. | ||
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and mainframe wiring harness for routing trigger and timing signals between the two units?'' | and mainframe wiring harness for routing trigger and timing signals between the two units?'' | ||
Some 661s have a 41 pin [[Bendix connector]], J5, on the rear panel, perhaps to allow the 661 to be interfaced to low speed data acquisition equipment or a computer. | Some 661s have a 41 pin [[Bendix connector]], J5, on the rear panel, | ||
perhaps to allow the 661 to be interfaced to low speed data acquisition equipment or a computer. | |||
This is essentially a pass-through from J2 & J3, the secondary multi-pin connectors on the vertical & horizontal plug-ins. | This is essentially a pass-through from J2 & J3, the secondary multi-pin connectors on the vertical & horizontal plug-ins. | ||
These connectors carry switch position information (number, magnitude & units) and clock & gate pulses. | These connectors carry switch position information (number, magnitude & units) and clock & gate pulses. |