TM 11-6625-2781-14&P-2
the rf input jack J1 may be defective. If the correct reading is
SERVICE SHEET 3
obtained reconnect A12 and proceed to step 2.
It is assumed that one or more of the following conditions
2. INPUT ATTENUATION ASSEMBLY A3.
exist:
Input attenuation assembly A3 provides 0 to 50 dB attenuation
1. The steps specified in Section IV, Paragraphs 4-12
in 10 dB steps using three fixed, pad type attenuators of 10,
through 4-13 have been performed; that only the marker and
20, and 30 dB. The INPUT ATTENUATION control is mainly
first local oscillator signals appear on the Display CRT, and
used to reduce the rf signal level applied to the first mixer to --
that there is no rf input to first converter A9 with an rf input
40 dBm or less. This minimizes distortion products generated
signal applied at J1. (Follow steps 1, 2, and 3.
in the mixer by operating the mixer in its linear' region. The
flat frequency response and attenuator accuracy contribute to
2. The index lamps do not function properly. (Follow step 4.)
the analyzer's absolute amplitude calibration.
3. Linear sensitivity as displayed on the CRT is incorrect.
TEST PROCEDURE
(Follow step 5.).
Since the input attenuator is difficult to remove, it should be
TROUBLESHOOTING PROCEDURE
tested in place and tests should include cable W1 and W2.
With the HP 8405A connected to the output end of cable W2,
Since there are no active components in the circuits to be
TP B (using the BNC tee, 50-ohm load, and jack-to-jack
tested, the 8553B should be disconnected from the IF section
adapter) and a 30 MHz, -10 dBm signal applied to the RF
and the mainframe.
INPUT, rotate the INPUT ATTENUATION control and
observe the meter for the following indications: 0 dB 10 dBm,
Following the procedures under individual circuit descriptions
10 dB 20 dBm, 20 dB 30 dBm, 30 dB 40 dBm, 40 dB -50
should isolate the defective circuit or component.
dBm, 50 dB 60 dBm. If the correct meter readings are not
observed the trouble is probably in Cable W1, Cable W2, or
All rf tests are conducted with a 30 MHz, -10 dBm signal
the attenuator assembly. If the readings are correct proceed
applied to RF INPUT connector J1.
to step 3.
EQUIPMENT REQUIRED
3. 20 MHz LOW PASS FILTER A11.
Vector Voltmeter . ...........................................HP 8405A
The 120 MHz Low Pass Filter is essentially flat up to 120
Volt-ohm-ammeter .............................................HP 410C
MHz, skirted to provide 3 dB of attenuation at 130 MHz, and
Service Kit ................................................ HP 11592A 50-
provides maximum rejection between 400 and 510 MHz.
Ohm Termination ...........................................HP 11593A
Signal Generator ................................................ HP 606B
TEST PROCEDURE:
Cable Assembly (2) .......................................HP 10503A
Jack-to-Jack Adapter ...............................HP 1250-0827
With an rf input signal connected as in previous steps,
BNC Tee . .................................................. UG 274 B/U
connect the HP 8405A (using the BNC Tee and the 50 ohm
load) to output connector J2 (TP C).
With INPUT
CONTROL SETTINGS.
ATTENUATION set to O dB and a -10 dBm signal applied to
As specified in individual tests.
RF INPUT J1, a reading of approximately -10.5 dBm should
be obtained. If reading is incorrect, the filter is probably
1. INPUT CAPACITOR ASSEMBLY A12
defective; if reading is correct, cable W3 to first converter
assembly A9 may be defective.
Input blocking capacitor A12C1 protects the diodes in the first
mixer during application of signals containing a dc
NOTE: If the low pass filter is replaced,
component. The breakdown voltage of the capacitor is in
it should be aligned in accordance with
excess of 50 Vdcw. From 1 kHz to 110 MHz, the response of
C1 is essentially flat.
SERVICE SHEET 2 (3 of 3)
TEST PROCEDURE
Overall Wiring and Switching Diagram
Disconnect the output connector from the A12 assembly.
Connect the HP 8405A to the A12 assembly TPA using the
test cable, BNC tee and 50-ohm load. This meter should
indicate -10 dBm.
If an incorrect reading is obtained the A12 assembly or
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