7. Clip off any excess leads that protrude through the
hole in the board.
8. If necessary, clean the area around the soldered con-
nection with a flux-remover solvent to maintain good envi-
ronmental characteristics,
Replacing Components on Metal Terminals
When soldering metal terminals (e.g., switch terminals,
potentiometers, etc.) ordinary 60/40 solder is satisfactory. The
soldering iron should have a 40- to 75-watt rating and a
1
/
8
inch chisel tip.
1. Apply only enough heat to make the solder flow freely
and form a good electrical connection. Excess solder may
impair the operation of the circuit or cover a cold solder
joint.
2. Clip off excess wire that may extend past the soldered
connection and clean with flux-remover solvent,
Removing and Replacing Switches
Single wafers on the VOLTS/DIV or DISPERSION-COUPLED
RESOLUTION switches are not normally replaced. If any of
these wafers are defective, the entire switch should be
replaced. It can be ordered through your Tektronix Field
office, either unwired or wired, as desired. Refer to the
Electrical Parts List to find the unwired or wired switch part
numbers.
C A U T I O N
W h e n d i s c o n n e c t i n g o r c o n n e c t i n g l e a d s t o a
w a f e r - t y p e s w i t c h , d o n o t l e t s o l d e r f l o w a r o u n d
and beyond the rivet on the switch terminal. Exces-
s i v e s o l d e r c a n d e s t r o y t h e s p r i n g t e n s i o n o f t h e
contact.
T R O U B L E S H O O T I N G
Attempt to isolate trouble to one circuit through opera-
tional and visual checks. Verify that the apparent trouble
i s a c t u a l l y a m a l f u n c t i o n w i t h i n t h e T y p e 4 9 1 a n d n o t
improper controls setting or malfunctioning associated equip-
ment. Note the effect the controls have on the trouble symp-
toms. Normal and abnormal operation of each control helps
establish the location and nature of the trouble, Control
functions are described in the Operations section.
Check the instrument calibration or the calibration of the
affected circuit. The trouble may be corrected after calibra-
tion, The calibration procedure is given in Section 6. Before
changing any adjustment settings during this check, note the
position of the adjustment, so it can be returned to its original
position after the check. This will facilitate recalibration after
the trouble has been found and corrected.
Check circuit voltages and waveforms against those shown
in section 9 of the manual. Fig. 4-22 through 4-26 provide
board wiring drawings and component layout information.
It is usually best, if the trouble is not isolated to a circuit,
Fig. 4-21. Electrode configuration for socket-mounted transistors and
field effect transistors.
4 - 1 8
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 ...