Model 8901B Service
TROUBLESHOOTING
General
Procedures for checking the RF Section of the instrument are given below. The blocks
or
points to
check are marked on the block diagram by
a
hexagon with a check mark and a number inside, for
example,
(J3)
.
Before performing any check, perform
all
the checks on Service Sheet BD1.
Tighten
SMA
connectors to
0.8
to
1.1
N.m
(7
to
10
imlb). Tighten
SMC
connectors to
0.6
N.
m
(5
in. lb). Hand tightening
of
connectors
is
insufficient. Hand-tightened connectors can work loose and cause reduced
performance
or
malfunctions.
Equipment
Oscilloscope
......................................................................
HP 1740A
Power Supply
.....................................................................
HP
6215A
Signal Generator.
.................................................................
HP
8640B
Spectrum Analyzer.
.........................................................
HP
8559A/182T
Voltmeter
........................................................................
HP 3455A
(J1)
Overpower Protection Check
1.
Press the blue key, then press INSTR PRESET (the AUTOMATIC OPERATION key)
to
preset
the instrument.
2.
Set the power supply to
20
Vdc. Touch the +20V lead to the Modulation Analyzer’s INPUT (the
minus side should be at ground). The display should show Error
06.
If
faulty, see Service Sheet
4
and check the Overpower Protection.
NOTE
If
step
2
is repeated, it
is
necessaly to first perform step
3
in order to
discharge the input dc blocking capacitor.
Also,
disconnect the supply
from
the
INPUT
before setting the voltage to
20
Vdc.
3. Set the supply to zero (without turning
it
off)
and while still connected
to
the INPUT,
press
CLEAR. Error
06
should go away.
If
it
doesn’t, see Service Sheet 4 and check the Overpower
Protection.
(J2)
RF
Detector Check
1.
Press the blue key, then press INSTR PRESET (the AUTOMATIC OPERATION key) to preset
the instrument. Connect the CALIBRATION RF POWER OUTPUT to A15J2 (RF IN).
2. Key in
45.16
SPCL to turn on the RF power calibrator. Key in
35.0
SPCL to measure RF level
with the RF peak level. The display should read between
0.6
and
1.6
mW.
If
faulty, see Service
Sheet
4
and check detector circuits.
(L/3)
Local
Oscillator Tuning Check
1.
Key in
54.0
SPCL.
If
the display shows other than
0,
see
Special &nction 54.N,
paragraph
8-7.
Service Sheet BD2 8D-21
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