F i g . 6 - 3 6 . T y p i c a l V i d e o F i l t e r i n t e g r a t e d d i s p l a y o f 2 0 0 M H z R F
division signal amplitude on the Type 491. Note the dBm
reading of the Signal Generator attenuator dial, Increase
the variable output attenuation of the Signal Generator
50 dB. Adjust the GAIN control for a 8 division display.
c. Check-Range of GAIN control must equal or exceed
50 dB.
N O T E
If the IF GAIN control does not meet this require-
ment, perform step 36 then recheck.
32. Check INTENSIFIER Control Range
a. Test equipment setup is given in step 29.
b . C h a n g e t h e D I S P E R S I O N s e l e c t o r t o 1 0 0 k H z / d i v .
Uncouple the RESOLUTION control and turn the control fully
clockwise (maximum resolution bandwidth).
c. Set the VERTICAL DISPLAY switch to LOG position than
adjust the GAIN control and the Signal Generator output
for a signal amplitude of approximately 8 divisions.
d. Turn the INTENSIFIER control to the OFF position (fully
C C W
). Set the INTENSIFIER control for a display of nominal
brightness. Set the CONTRAST adjustment to midrange.
e. Turn the INTENSIFIER control fully
C W
. The intensified
portion of the signal should measure between 3.5 and 4.5
major divisions.
Fig. 6-37. Typical display showing incidental frequency modulation,
3 3 .
a.
b.
Check Signal Amplitude at the TO
RECORDER Connector
Equipment setup is given in step 29.
Set the VERTICAL DISPLAY switch to the LIN position,
adjust the Signal Generator output and the Type 491 GAIN
control for a signal amplitude of 6 divisions.
c. Connect a
1×
probe from the test oscilloscope to the
TO RECORDER connector on the back panel. Terminate the
connector into a 600 W Ioad by connecting a 600 W resistor
from the TO RECORDER lack to ground.
d. Check—Signal amplitude should equal or exceed 24
mV
(≥4
mV division of displayed signal amplitude).
34. Check Video Filter Operation
a.
Equipment setup is given in step 33.
b . W i t h t h e D I S P E R S I O N s e l e c t o r a t 1 0 0 k H z / D I V a n d
the TIME/DIV at 5 ms, uncouple the RESOLUTION control
and turn counterclockwise one position from the full clock-
wise position.
c . T u r n t h e V I D E O F I L T E R s w i t c h O N .
d. Check—The display should resemble Fig. 6-36.
e. Decrease the TIME/DIV to .5 s position and check the
display. There should be no appreciable change in the
display, when the FILTER is switched ON or OFF, unless there
is noise in the display. Set the FILTER to the OFF position.
6 - 3 4
Summary of Contents for 491
Page 4: ...i i Fig 1 1 The Type 491 Spectrum Analyzer ...
Page 24: ...2 16 Fig 2 17 Control set up chart ...
Page 34: ...Fig 3 1 Function block diagram of the Type 491 3 2 ...
Page 42: ...Fig 3 10 Block diagram of the video detector and vertical amplifier 3 1 0 ...
Page 48: ......
Page 53: ...Fig 4 4 Power Supply Circuit board assembly with wiring color code 4 5 ...
Page 54: ...Fig 4 5 Horizontal Display circuit board assembly showing color code to pin connectors 4 6 ...
Page 55: ...Fig 4 6 IF Control board assembly Wiring color code to pin connector 4 7 ...
Page 64: ...Fig 4 20A Tube subassembly removal procedure 4 16 ...
Page 65: ...Fig 4 20B Tube subassembly installation procedure 4 17 ...
Page 68: ...Fig 4 22 Power supply board assembly with component call out 4 2 0 ...
Page 69: ...Fig 4 23 Vertical Amplifier and Blanking board assembly with component call out 4 21 ...
Page 70: ...Fig 4 24 IF control board assembly with component call out 4 22 ...
Page 71: ...Fig 4 24 IF control board assembly with component call out 4 23 ...
Page 72: ...Fig 4 25 Horizontal display board with component call out 4 24 ...
Page 73: ...Fig 4 25 Horizontal display board with component call out 4 25 ...
Page 74: ...Fig 4 26 Phase lock board with component call out 4 26 ...
Page 88: ......
Page 90: ...Fig 6 1 Test equipment recommended for calibration of the Type 491 6 2 ...
Page 138: ......
Page 192: ......
Page 195: ...SECTION II B 3 ...
Page 196: ......
Page 200: ......
Page 201: ...SECTION 9 DIAGRAMS MECHANICAL PARTS LIST ILLUSTRATIONS ACCESSORIES ...
Page 202: ......
Page 203: ...9 1 ...
Page 204: ...9 3 ...
Page 205: ...9 5 ...
Page 206: ...9 7 ...
Page 207: ...9 9 ...
Page 208: ...9 11 ...
Page 209: ...9 13 ...
Page 210: ...9 15 ...
Page 211: ...9 17 ...
Page 212: ...9 19 ...
Page 213: ...9 21 ...
Page 214: ...9 23 ...
Page 215: ...9 25 ...
Page 216: ...9 27 ...
Page 217: ...FIG 1 9 29 ...
Page 218: ...FIG 2 REAR 9 31 ...
Page 219: ...9 33 FIG 3 IF CHASSIS PHASE LOCK ASSEMBLIES ...
Page 220: ...FIG 4 POWER CHASSIS 9 35 ...
Page 221: ...FIG 5 TIME DIV SWITCH OSCILLATOR ASSEMBLIES 9 37 ...
Page 222: ...FIG 6 CRT SHIELD ASSEMBLY 9 39 ...
Page 223: ...FIG 7 CABINET ASSEMBLY HANDLE 9 4 1 ...
Page 224: ...FIG 8 491 STANDARD ACCESSORIES FIG 8 491 STANDARD ACCESSORIES 9 43 ...
Page 225: ......
Page 226: ...PIN 028017 000 ...