Filter
Top Products
Adjustment Procedures
1780R-Series Service Manual
5–27
NOTE. To eliminate generator signal DC level error, if present, when performing
parts e. through h. of this step, select COUPLING-GND on PAGE 1 of the
Configure menu. Use the VERT POS control to position the trace to the
Waveform CRT graticule baseline. Perform parts e. through h. and j. through m.
f. Set the WAVEFORM GAIN-X5 to On.
g. Use the VERT POS control to position the backporch to the graticule
baseline.
h. Adjust X5 Gain Regis (A2R526) for minimum back porch or blanking
level DC shift between the X5-On and X5-Off WAVEFORM GAIN
selections. This is accomplished by using the VERT POS control to
move the blanking level to the graticule baseline in the X5-On mode.
Then go to X5-Off and adjust A2R526 so that the blanking level is
repositioned back to the graticule baseline. Alternate WAVEFORM
GAIN between X5-Off and X5-On and repeat the procedure until the
movement is minimum.
i. Press the CONFIGURE button and select COUPLING-GND for no
signal input.
j. Check that the button below the Waveform CRT is On. Press the
CALIBRATE button and select TRACE ROTATION on the Vectorscope
CRT.
k. Readjust Vertical Readout Pos (A2R309) to position the + marks of the
Waveform CRT electronic graticule with the 0 IRE (0.3 for PAL)
graticule baseline.
l. Press the CALIBRATE button to exit the menu. (Leave COUPLING-
GND selected on the Configure menu.)
m. Disconnect the Color Bar signal from the CH A INPUT.
19. Adjust Output Gain
a. Reconnect the VAC output to one of the 1780R-Series CH A INPUT
connectors. Check that the Black Burst signal is applied to the EXT REF
connector.
b. Press the CONFIGURE button and select DC RESTORER-OFF. Check
that COUPLING-GND is selected.
c. Select RIGHT DISPLAY-WFM+CAL mode. Check that the VAC is set
for 999.9 mV.
d. Set the WAVEFORM GAIN to VAR and adjust the variable WAVE-
FORM GAIN control fully counterclockwise for minimum gain as
displayed on the Waveform CRT.