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Model 5065A
C i r c u i t Diagrams, Theory, and Maintenance
CONNECTOR NAME
+24
+20
+EFC OR ■
1V
DIV
+15
M
-EFC
INPUT OR
OUTPUT
INPUT
INPUT
INPUT
OUTPUT
OUTPUT
OUTPUT
OUTPUT
SIGNAL CHARACTERISTIC
+22 to +30 Vdc primarily for oven heater power (about
160 mA is normal; about 450 mA during warm-up).
+18 to +22 Vdc for oscillator and output circuits (50 mA
nominal).
Voltages to control A10 output frequency.
5 MHz sine wave output. At least 1.0 Vrms into a 50-ohm
load.
5 MHz sine wave output. Nominal 50 mV to 150 mV rms
into 1000-ohm load.
+14.0 to +15.8 Vdc for fine frequency control (OSC FREQ
FINE).
To OSC OVEN position of CIRCUIT CHECK METER via
A17 Terminal Board.
OVEN OPERATION
Use the following procedure to check operation of the
A10 oven:
a. Apply power to 5065A and allow at least 1 hour
warm-up period. Set CIRCUIT CHECK METER to
OSC OVEN.
b. Meter indication should be as indicated in Table 3-
1. Failure of this test indicates failure of A10A110
MHz oscillator, or circuit of A10A3Q2.
+15V REFERENCE SUPPLY CHECK
Measure voltage at "+15" jack on A10A2. Voltage
should be between +14.0 and +15.8 Volts dc.
OUTPUT AMPLITUDE AND DISTORTION CHECK
Output amplitude at the "IV" jack should be at least 1.0
Volt rms into 50 Ohms. Output harmonics of 5 MHz at
the "IV" jack should be at least 30 dB below the 5 MHz
output. Output at "DIV" jack should be from 50 mV to
150 mV rms.
a. Disconnect cable at "IV" jack on A10 Oscillator
Assembly.
b. Use a Micon-to-BNC test cable and a 50-ohm
feedthrough to connect "IV" jack to the vertical
input of an oscilloscope. The displayed waveform
should be a sine wave of at least 2.8 Volts p-p. This
level can be adjusted with A10A2R8.
c. Remove 50-ohm feedthrough and connect signal to
spectrum analyzer. Check spectrum from 5 MHz to
20 MHz. All 5 MHz harmonics should be more than
30 dB below the 5 MHz output.
d. Disconnect spectrum analyzer and reconnect
5065A cable on "IV" jack.
e. Use high impedance oscilloscope probe to measure
voltage at "DIV" output on circuit side of A10A2
circuit board. Oscilloscope should indicate 140 to
420 mV p-p (50 to 150 mV rms).
SHORT TERM STABILITY CHECK
a. Allow HP 5065A to operate at least one hour. Set
FUNCTION to LOOP OPEN.
b. Disconnect cable from A10 "IV" connector and
connect cable to an HP 5390A Frequency Stability
Analyzer (FSA).
c. Perform short-term stability test of Table 5-2
(Performance Test, step 8). NOTE: This is a test of
the oscillator assembly so the analyzer must be
connected to the "IV" output on A10 rather than
the 5 MHz front-panel output. All other test
conditions remain the same.
The measured stability should be equal to or better than
5 X 10-12 for a one second averaging time. Failure of this
test indicates a problem in A10A2 Divider Amplifier
Assembly, or A10A1 oscillator. A10A1 may be checked
independently.
EFC CHECK
This test checks operation of Electronic Frequency
Control (EFC) input to A10.
a. Set CIRCUIT CHECK switch to 2ND HARMONIC
and MODE to LOOP OPEN. Turn OSC FRE
QUENCY FINE control maximum counterclock
wise, maximum clockwise, and then back to 250.
The CIRCUIT CHECK meter should respond to
control movement.
b. Disconnect cable from "-EFC" jack on A10.
Connect dc power supply minus (-) lead to "-EFC"
jack and power supply (+) to chassis. Slowly adjust
power supply from 0 to 5V. CIRCUIT CHECK
METER should respond to power supply adjust-
(SERIES 2120A)
8-51
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