Log Amplifier-Detector, Troubleshooting
If the amplitude of the displayed signals is approximately 10 low (CAL OUTPUT appears
to be -20
in the log mode but correct in the linear display mode, then one of the log
amplifier stages in the
Log Amplifier-Filter board or the
Log Amplifier-Detector
board is defective. Connect a 10 step attenuator between the CAL OUTPUT and the
spectrum analyzer input. Refer to the Log Amplifier Stage Gain Check note on the service
sheets for the necessary front-panel control settings. When forward biased in log mode, the
Schottky diodes should have voltage drops of 200 to 400
The following procedure will determine if the Linear Gain Steps,
and LG20, are
operating properly. The
circuitry is located on the
Log Amplifier-Filter board
while the LG20 circuitry is located on the
Log Amplifier-Detector board. Connect a
10 step attenuator set to 0 between the CAL OUTPUT and the spectrum analyzer
input. Press Instrument Preset and key in the following settings:
(
C E N T E R
. . . . . . . . . . . . . . . . . . . . . . . . .
equal to the CAL OUTPUT frequency
S P A N
) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
10
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0
LOG SCALE
(
ENTER
(Turns off IF Step Gains)
(
R E F E R E N C E L E V E L
)
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
SCALE LIN
The peak of the displayed signal should be on the top graticule. Adjust the front panel
AMPTD CAL control to place the peak of the signal one division below the top graticule.
If the signal limits at the top of the display, one of the Linear Gain Steps is stuck in the on
state.
Set the 10 step attenuator to 10
and key in
(
REFERENCE LEVEL
)
-70
The peak
of the displayed signal should be one division below the top graticule. If signal limits at the
top of the display, the LG20 circuitry is defective. A signal approximately 3 divisions high
indicates the
circuitry is defective.
Set the 10 step attenuator to 20 and key in
(
REFERENCE LEVEL
)
-80
The peak
of the displayed signal should be one division below the top graticule. The
circuitry
is defective if the signal limits at the top of the display. The LG20 circuitry is faulty if the
displayed signal is approximately 3 divisions high.
The detector circuit on the
Log Amplifier-Detector board is most easily checked with
dc voltages. These are derived using 0 Hz
(
CENTER FREQUENCY
)
and attenuating the CAL
OUTPUT signal. The easiest point to check the Detector output without removing boards is
Connect a DVM to this test point. The voltage at
should be V for
a signal displayed on the top graticule. The output will be 0.1 V less for each division down
from the top in either the linear or the 10
log modes when the detector is operating
properly.
4
Содержание 85662A
Страница 13: ......
Страница 14: ......
Страница 17: ...can cause the CRT to be disabled If U14 is operating correctly visually inspect the A4A9 assembly Al 3 ...
Страница 18: ......
Страница 27: ......
Страница 28: ...AlA KEYBOARD Al Front Panel Assembly and Component Locations ...
Страница 30: ......
Страница 49: ......
Страница 51: ...3 AlA XYZ Driver Amplifier Component Locations 85662 60236 ...
Страница 52: ......
Страница 53: ......
Страница 54: ......
Страница 72: ......
Страница 73: ......
Страница 77: ......
Страница 78: ......
Страница 84: ......
Страница 92: ...V I E W A AlA lII1 0 O0 4 JII fi V I E W B Figure 1 IF Display Section internal Fuse Replacement 8 Al A6 Al A7 ...
Страница 108: ......
Страница 109: ......
Страница 111: ...I 1 AlA f15 V Regulator Component Locations 85662 60232 85662 60250 ...
Страница 113: ......
Страница 114: ......
Страница 115: ......
Страница 122: ......
Страница 124: ...DSl M A I N S I N D I C A T O R C6 CATHODE 4 1 El r l CR9 P I AlA Rectifier Component Locations 85662 60204 ...
Страница 125: ...c 4 C 6 R 6 I 0 C R 9 0 CR10 AlA Rectifier Component Locations 85662 60234 ...
Страница 126: ...0 El E2 r r L J L J _ I 0 0 0 0 AlA Bus Transition Component Locations 85662 60056 ...
Страница 127: ......
Страница 128: ......
Страница 129: ......
Страница 131: ......
Страница 133: ......
Страница 142: ......
Страница 161: ......
Страница 163: ......
Страница 178: ......
Страница 179: ... R51 Y S H BAL R50 X S H BAL R12 LL THRESH A3A2 Intensity Control Component Locations 85662 60025 85662 60245 ...
Страница 180: ......
Страница 181: ......
Страница 195: ......
Страница 196: ...R 8 YSL L Il ln R IC7n XSL 0 0 0 R 5 I I Y G A I N R 2 Y E X P A3A3 Line Generator Component Locations 85662 60128 ...
Страница 198: ......
Страница 203: ......
Страница 205: ......
Страница 210: ......
Страница 212: ......
Страница 216: ...Verify binary count sequence starting at the least significant bit SO 500 ns square wave to S7 64 ps square wave 4 A3A6 ...
Страница 219: ......
Страница 221: ......
Страница 226: ......
Страница 228: ......
Страница 241: ......
Страница 256: ......
Страница 258: ...R 5 7 T H G A I N R59 T H O F S A3A9 Track and Hold Component Locations 85662 60165 ...
Страница 259: ......
Страница 260: ......
Страница 262: ...ASXAlPI I A3XA2P 1 AJXAJP 1 A3XA4P 1 A3XA5P 1 A3XA6Pl A3XA7P 1 A3XA9P 1 AJXAlP2 A3XA2P2 A3XASP2 A3XA6P2 A3XA7P2 ...
Страница 263: ......
Страница 266: ......
Страница 274: ......
Страница 275: ...R2 LG OS p 10 C6 I I R14 ar OS 1 5 1 A4Al Video Processor Component Locations 85662 60122 ...
Страница 276: ......
Страница 293: ......
Страница 294: ...2 k 4 5 7 J2 F1 TEN R91 12VTV R14 LG 20 A4A2 Log Amplifier Detector Component Locations 85662 60132 ...
Страница 295: ...2 4 5 1 0 N a R79 ZERO 4 E N TV R14 LG 20 A4A2 Log Amplifier Detector Component Locations 85662 60166 ...
Страница 296: ......
Страница 297: ......
Страница 315: ......
Страница 316: ...10 A 1 2V T Y P 7 V T Y P A4A3 Log Amplifier Filter Component Locations 85662 60009 ...
Страница 318: ......
Страница 319: ......
Страница 321: ... 15v t15v cl7 ETC Figure 2 A4A4 Input Buffer Amplifier Current Sinks 2 A4A4 ...
Страница 334: ......
Страница 336: ...c 4 3 L C D I P c41 L C D I P A4A4 Bandwidth Filter Component Locations 85662 60189 TR ...
Страница 337: ......
Страница 338: ......
Страница 352: ......
Страница 354: ......
Страница 363: ......
Страница 365: ...A4A8A2 Down Converter Component Locations 85662 60005 ...
Страница 366: ...c31 R29 1 8 4 M H z NULL W I D E G A I N A4A6Al Up Converter Component Locations 85662 60006 ...
Страница 367: ......
Страница 379: ...c40 c 4 1 PK SYM y Hz A M P L 10 Hz AMPL A4A7 3 MHz Bandwidth Filter Component Locations 85662 60004 85662 60174 ...
Страница 380: ......
Страница 399: ......
Страница 402: ......
Страница 403: ......
Страница 409: ...Table 4 Video Bandwidth Truth Table 6 A4A9 ...
Страница 428: ......
Страница 429: ......
Страница 430: ......
Страница 434: ......
Страница 447: ......
Страница 452: ...A4A6A2 Output Driver Component Locations 85662 60170 Option 067 Tab ...
Страница 453: ...A4A6Al Input Buffer Component Locations 85662 60171 Option 067 Tab ...
Страница 454: ......
Страница 470: ......
Страница 473: ...Table 4 Video Bandwidth Truth Table Option H96 3 ...
Страница 498: ......
Страница 504: ...Table 4 Video Bandwidth Truth Table 100 Hz H 30 Hz H H 10 Hz H 3 Hz H 1 Hz 6 Option 462 ...
Страница 514: ......
Страница 523: ......
Страница 531: ......
Страница 548: ......
Страница 549: ......
Страница 550: ......
Страница 582: ...This page intentionally left blank 32 General Parts Listing ...
Страница 594: ...HEWLETT PACKARD HP Part No 85662 90085 Printed in USA ...