HP 5065A Operating And Service Manual page 203

MAINTENANCE
Synthesizer Assembly A1
NORMAL OPERATION
The A1 Synthesizer Assembly processes 5 MHz to pro­
duce the required 5.315...MHz. This is added to the A3
Multiplier 60 MHz output and multiplied to 6,834,685
Hz by the step-recovery diode in the RVFR Assembly.
To obtain proper Synthesizer output frequencies for
UTC and A1 operation, the Synthesizer output is adjust­
able by the TIME SCALE slide switch and thumbwheel
switch located under the top cover of the 5065A. Output
frequencies corresponding to all the TIME SCALE
settings can be found in Table 3-6 of OPERATION. The
thumbwheel switch setting for A1 operation is listed in
the RVFR decal. The thumbwheel switch setting for
UTC operation is listed on the front panel door.
PERFORMANCE CHECK
If trouble is suspected in the A1 Synthesizer Assembly,
the following checks will verify proper or improper
operation.
a. Phase Lock Check. Remove top and bottom
covers. Connect an oscilloscope to A1TP1 (on bottom
of instrument). If the waveform is a random AC signal then
the phase-locked oscillator section of the Synthesizer is
out of lock. Check thumbwheel and HI/LO switch settings
to be sure they are correct. If these switch settings are OK,
troubleshoot Synthesizer circuit as described under A1
Troubleshooting. If signal at A1TP1 is correct, check Syn­
thesizer output frequencies versus the thumbwheel set­
tings as described in the following paragraph.
b. Synthesizer Frequency Check. Set up 5065A,
frequency counter, and RF voltmeter as shown in Fig­
ure 2.
Note thumbwheel and HI/LO switch settings on A1 Syn­
thesizer Assembly. Go to Table 3-6 in OPERATION and
determine the frequency corresponding to these settings.
The counter should read this frequency ±1 count. The RF
voltmeter should indicate 100 mV rms or more. If the
counter and RF voltmeter readings are correct, the Syn­
thesizer is working properly at this setting.
A further check of Synthesizer operation at several
points over its operating range can be made by setting
the switches and reading the frequencies shown in the
table below. All frequency readings should be within
+1 count; RF voltmeter should read 100 mV or greater.
Thumbwheel Switch
Setting
9000
9159
9635
8714
9603
9047
8777
8697
9253
8919
7758
9348
HI/LO
Switch
HI
HI
HI
HI
HI
HI
HI
LO
LO
LO
LO
LO
Frequency (Hz)
5315000.0
5315101.1
5315068.5
5314930.0
5314861.5
5314795.4
5314700.7
5314658.5
5314591.7
5314523.6
5314451.4
5314417.2
NOTE
If the thumbwheel switches are changed
from one setting to another or service is
performed on A1, allow at least 1 minute
of recovery time before attempting to
get the continuous operation lamp to
light.
TROUBLESHOOTING (See Figure 1).
To check out the Synthesizer circuits, pull off the elec­
trical snap-on connectors and remove four screws which
fasten the Synthesizer Assembly to the bottom of the
chassis. With the bottom cover removed, turn the unit
over for access to the electrical connectors at the chassis
bottom. Remove the Synthesizer cover. Check that line
power is disconnected. Then lay the Synthesizer
Assembly on the bottom of the chassis with some in­
sulation to prevent shorts. Make electrical connections;
the snap-on plugs for the shielded leads are labeled with
plug number and the pin connectors for the colored-
wire connections are labeled for wire color.
Figure 1.
+20VDC
5MH7
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