F i g . 4 - 7 . H o n e y c o m b a s s e m b l y a n d w i r e c o l o r c o d e t o t h e p i n
connector.
3. Turn
the Type 491 on its side (see Fig. 4-11). Remove
the nylon rocker arm from the DISPERSION RANGE switch
SW365.
4. Unlock the IF control assembly and swing the circuit
b o a r d a s s e m b l y u p t o i t s f u l l y e x t e n d e d p o s i t i o n . N o w
gently remove the honeycomb assembly by slipping the
assembly towards the rear to free the mounting screw head
and pulling the assembly out and to the rear.
5. Turn the honeycomb assembly over and place it upside
down on a block or box as shown in Fig. 4-11. CAUTION-
Do not bend or damage the pin connectors.
6. Remove the screws that fasten the bottom plate to
the assembly and remove the bottom plate.
7. If power is to be applied, make certain all connections
are correct to the square pin connector and the connectors
are free of short circuit conditions. The DISPERSION RANGE
switch must be manually switched on the honeycomb assem-
b l y w h e n c h a n g i n g D I S P E R S I O N R A N G E p o s i t i o n s . F i g .
4-11 shows the circuit sections in each cell of the honey-
comb assembly.
Cathode-Ray Tube Replacement
Protective clothing and safety glasses should be worn when
handling the CRT. Avoid striking the tube on any object which
might cause the tube to crack or implode. The CRT may be
stored by placing the tube face down on a smooth surface
with a protective cover or soft mat under the faceplace to
prevent scratches.
The removal and replacement procedure for the CRT tube
and shield assembly is as follows:
1. Unsolder the trace rotation leads.
4 - 8
Fig. 4-8. Connector assembly board for the RF oscillator assembly
and wiring color code to the pin connector.
2. Disconnect the deflection plate pin connectors, Pull
out on the connectors so the pins will not be bent.
3. Remove the CRT base socket,
4. Remove the two (2) nuts and graticule light holders
which secure the front of the CRT shield to the subpanel.
Remove the graticule lights from the studs and position them
out of the way.
5. Remove the two phillips-head screws that hold the two
right angle mounting brackets at the base of the CRT shield.
See Fig. 4-12.
6. Slide the CRT assembly to the rear of the instrument
until the faceplate clears the mounting studs; twist the
assembly clockwise to clear the right angle brackets, then
lift the assembly up and out of the instrument.
7. Loosen the slot screw at the base of the CRT clamp
inside the CRT shield.
8. Place the left hand on the CRT faceplate and push
forward on the tube base with the right hand to slip it out
of the base clamp. As the CRT starts out of the shield, grasp
it firmly with the left hand. When the tube is free of the
clamp, slide the shield completely off the CRT.
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 ...