ponent can then be correctly soldered in its place, Observe
soldering precautions and techniques as described in Solder-
ing Techniques later in this section.
The interconnecting wires to the boards are sufficiently
long that the boards may be loosened and re-positioned
for troubleshooting without disconnecting the pin connectors.
The procedure for removing these circuit board assemblies
is as follows:
1. Remove the mounting screws holding the board in posi-
tion.
2. Slip the cable out of the delrin cable clamps if the
IF board is to be removed.
3. Disconnect the necessary pin connectors to allow the
board to be lifted and turned as required for maintenance.
4. If complete removal is desired, remove all the pin con-
nectors and soldered leads.
5. To replace the board, reverse the removal procedure.
Correct wire and pin connections for each circuit board
assembly are shown in Figs. 4-3 through 4-9.
Make certain the pin connectors are perpendicular with
the pins when connecting to prevent bending or spreading
the pin connectors. If the connectors are grasped near the
wire end by a pair of needle nose pliers, their removal
or installation is relatively easy.
Removal of the High Voltage Compartment
Components in the high voltage compartment can be
removed far maintenance or replacement as follows:
1. Remove the two mounting screws and high voltage
shield over the compartment.
2. Slide the high voltage components out of the plastic
compartment and replace as necessary.
3. Reverse the procedure for replacing the high voltage
assembly.
Removing the Honeycomb Assembly
1. Remove the six (6) nuts and washers that hold the IF
A T T E N U A T O R d B s w i t c h e s a t t h e f r o n t p a n e l a s s e m b l y .
2. Remove the chassis mounting screw and grounding
lug located at the outside rear end and loosen the inside
rear mounting screw. See Fig. 4-10.
F i g . 4 - 3 .
Vertical Amplifier circuit board with wiring color code to pin connectors.
4-4
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 ...