Sect. IV Page 12
B. ADJUST THE CALIBRATOR OUTPUT Physical location and numbering of the Horizontal
Amplifier adjustments has varied with production.
1) Set the CALIBRATOR switch to the 6.3 V AC Assembly No. 150A-65B is shown in Figure 4-4A,
positionand check the voltage at the calibrator out- Assembly No. 150A-65F is shown in Figure 4-4B.
put terminal; it should be approximately 6.3 volts
rms.
A. ADJUST HORIZONTAL AMPLIFIER GAIN
2) Remove tube V32. Connect a dc vacuum tube Gain adjustment is keyed to Sweep Generator tim-
voltmeter with a high input resistance to theCALI- ing components. Refer to, the different SWEEP
BRATOR output terminal. TIME/CM SWITCH DETAIL drawings (Figure 4-
12A,4-12B and 4-12C)and compare circuits to find
3) Set CALIBRATOR to 100 volts output. Adjust one that agrees with the oscilloscope being adjusted.
R290to set the dc voltage at theCALIBRATOR out- Circuit configuration and.notes on the switch draw-
put terminal to +100volts. If R290adjustmentrange ings indicate proper setting for gain adjustment.
is .lot wide enough to permit setting this voltage,
try replacing CR1 and/or CR2 diodes. Diode CR1 1) Setthe HORIZ. SENSITIVITY control to the un-
is located on the underside of the high voltage power marked vertical test position.
supply and calibrator board at the top rear of the
instrument. Diode CR2 is located on the CALI- 2) Set the CALIBRATOR to 10 VOLTS and connect
BRATOR switch. to the EXT. HORIZ. INPUT.
4) The remaining voltages, measured with a dc 3) Slowly adjustR199 to give a horizontaldeflection
voltmeter, should fall within *3% of the indicated of 5.0 or 5.6 centimeters. It will be necessary to
CALIBRATOR output. Checking the accuracy of adjust the HOFUZ. POSITION control to keep the
the 50 through .1 volt ranges will verify all ranges. spots centered.
5) Replace V32. 4) Adjust C80 or C82 (whichever is variable) to eli-
minate any overshoot or undershoot on the spots.
C. TEST THE CALIBRATOR GROUND CLAMP Proper adjustment produces well defined spots with
no "tails."
1) The CALIBRATOR square wave symmetry should 5) Disconnect all cables.
be better than 40-60%. Replacing V32 will usually
restore symmetry.
B. ADJUST HORIZONTAL, AMPLIFIER BALANCE
2) Set CALIBRATOR to 1 VOLT and connect the
CALIBRATORoutput to the test oscilloscope verti- 1) Set the HORIZ. SENSITIVITY control to XlOO and
cal input. adjust theHORIZ. POSITIONto bring the spot to the
approximate center of the CRT. Keep the INTENSITY
3) Set the test oscilloscope for positive-up dc and a low to avoid burning the phosphor.
vertical deflection sensitivity of 1 volt per centi-
meter. Position the bottom of the square wave -2) Switch to the X5 range and note the location of
CALIBRATOR signal across the center of the test the spot. Switch back to XlCO and return the spot
oscilloscope screen. to the location notedwhen on theX5 range using the
HORIZ. POSITION control
4) Rotate the CALIBRATOR to 20 VOLTS Jf the
bottom of the square wave shifts vertically more 3) Center the spdt with R207. .. '
than 1 centimeter, diode CR2 is defective and must
be replaced. A certain amount of shift can be ex- 4) Switch from X5 to X1 and note the spot shift.
pected due to overload of the test oscilloscoDe ver- Adiust R189 for minimum swt shift when switch-
tical amplifier. , . ing between X1 and X5.
5) Repeat paragraphs 4-8A and 4-8B until both
4-8 HORIZONTAL AMPLIFIER balance and gain are correct.
'I
The horizontal am$ifier is located on the left side
of the instrumenton a swingoutchassis. The chas- C. TEST HORIZONTAL AMPLIFIER FOR HUM
sis is locked in place by a captive fastener, or a
screw near the center of the board next to the panel., ~ 1) Set the HORIZ. SENSITIVITY switch to XI, stop |
ACEC
HEWLETT-PACKARD
