33 Controls And Indicators


3-5. Figure 3-1 identifies the front panel controls, indicators, and terminals, and provides a short description of their functions.

3-6. BEAM FINDER OPERATION. Frequently the CRT trace can be driven off the CRT screen by excessive DC input levels or by misadjustment of position or balance controls on the plug-ins. When the BEAM FINDER switch is depressed, the beam is confined to the screen of the CRT. If the trace is centered with the position and/or balance control when the BEAM FINDER is depressed (see manual for plug-in for specific instruction), the trace will remain on screen when the BEAM FINDER is released.


At high amplifier sensitivities a further slight adjustment of the balance control may be necessary. Failure of the BEAM FINDER to bring the trace on screen may generally be attributed to insufficient intensity or unusually high DC signal input. It should also be noted that when single-sweep operation is used with a time base plug-in, the spot at the end of a single sweep will be blanked by termination of the gate.

3-7. TRACE ALIGN ADJUSTMENT. To compensate for slight manufacturing tolerances and external magnetic disturbances, a front panel screwdriver adjustment has been provided to align the trace with the graticule. Adjust TRACE ALIGN whenever realignment of the trace seems necessary. A check should be made after moving the instrument to a new operating location.

3-8. ASTIGMATISM ADJUSTMENT. To provide uniform focus of the trace over the display area, the ASTIGMATISM control, a front panel screwdriver adjustment, is used in conjunction with the FOCUS control. For correct adjustment, adjust both FOCUS and ASTIGMATISM for sharpest display of signal. Because different plug-ins will apply different DC potentials to the deflection plates, it will usually be necessary to readjust ASTIGMATISM whenever plugins are changed.

3-10. 115/230. This switch, located at the bottom of the rear panel, must be set to the nominal line voltage before plugging the power cable into the service outlet.

3-11. Z-AXIS INPUT. The Z-AXIS INPUT terminals and selector switch are located on the rear panel of the instrument. To externally modulate the trace intensity, set the selector switch to EXT, and apply modulating signal to Z-AXIS INPUT terminals. The amplitude of modulating pulse required to blank the trace depends upon the level of beam intensity, and is about 20 volts positive for average intensities. Conversely, a negative pulse can be applied to the Z-AXIS INPUT to intensify the trace. When not using the terminals, be sure that the ground strap is in place. When the oscilloscope is used with a dual channel plug-in, the selector switch should be placed in the INT position. This will connect the chopper blanking pulse to the CRT cathode, so that switching transients will be blanked out when the plug-in is being used in the chopped mode of operation.

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