![Tektronix 491 Maintenance Manual Download Page 98](http://html1.mh-extra.com/html/tektronix/491/491_maintenance-manual_1077911098.webp)
c. Connect the voltmeter between pin 14 of the CRT base
socket and chassis ground. (See Fig. 6-6). Set the voltmeter
range to measure approximately 4000 volts.
d. Turn the POWER switch to ON and adjust the High
Voltage Adj R1000 (Fig. 6-6) for a meter reading of –3670
volts.
e. Turn the POWER switch to OFF, remove the meter lead
probes and replace the plastic protective cover over the
CRT base. (Align the two holes in the cover to the holes
inthe socket),
4. Adjust Intensity Range
o
a. Test equipment setup is given in step 3.
b . T u r n t h e P O W E R s w i t c h t o t h e O F F p o s i t i o n , t h e n
remove the high voltage fuse F1008.
c. Connect an ammeter across the fuse holder (Fig. 6-7)
Set the ammeter range to 1A.
d. Turn the vertical POSITION control fully counterclock-
wise to position the beam off the CRT screen, turn the
P O W E R s w i t c h t o O N a n d t h e I N T E N S I T Y c o n t r o l f u l l y
clockwise.
NOTE
Be careful not to exceed 800 mA meter reading.
If the Intensity Range is misadjusted, the current
may exceed 800 mA and blow the high voltage
fuse.
e. Adjust the Intensity Range R1032 for a current read-
ing of 750 mA.
f . T u r n t h e P O W E R s w i t c h t o O F F , r e m o v e t h e m e t e r
leads and replace the high voltage fuse. Check that the
fuse is a 1A fast blow. Turn the POWER switch to ON, then
readjust the INTENSITY and POSITION controls for a cen-
tered trace of nominal brightness.
5. Check Power Supply Voltage Regulation and
Ripple Amplitude
a. Test equipment setup is given in step 4.
b. Connect the VOM to the voltage check paints (Fig. 6-5),
and check the voltage regulation of each regulated supply
as the input line voltage is varied through the input line
voltage range as shown in Table 6-1.
Connect the
1×
probe from the test oscilloscope to the
voltage check points and note the ripple amplitude. Volt-
age regulation and typical ripple amplitudes are listed
in Table 6-2.
The input line voltage to the Type 491 is adjusted by
means of the autotransformer which is connected between
the source and the Type 491 input power connector.
T A B L E 6 - 1
L i n e V o l t a g e
I n p u t V o l t a g e R a n g e
S e l e c t o r
L O W
90-110 VAC
MED
104-126 VAC
H I G H
112-136 VAC
6-10
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 ...