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Model 5065A
Circuit Diagrams, Theory, and Maintenance
100 kHz FREQUENCY DIVIDER A4 THEORY
The 100 kHz divider consists of a tuned 1 MHz input
amplifier, an integrated circuit decade divider and two
tuned output amplifiers. Low pass filters and traps are
used to shape the I.C. divider output and to reduce
harmonic distortion.
The filtered signal drives two
tuned amplifiers which provide the sine-wave outputs.
The 1 MHz input signal from A6(9) is amplified by Q1
and saturating transistor amplifier Q4. Decade divider
IC1 provides a symmetric 100 kHz square wave at
IC1 (12). The divided output is amplified and shaped by
Q5 and Q7 and is available at A4(14). The divided out
put is also amplified by Q6, Q8, and Q9 and is available
as the 100 kHz output to J1 and J10. A portion of this
output is rectified by CR2, filtered by C23, R35, and dis
played on front-panel meter at the 100 kHz position.
The 1 MHz input signal is also coupled through emitter-
follower Q2 and provides the 1 MHz signal to A5 Digital
Divider.
NORMAL OPERATION
The A4 Circuits process the 1 MHz from A6 to pro
duce 100 kHz. An output from A4 is available anytime
a 1 MHz signal is fed into A4(6). The A4 outputs are:
a.
100 kHz 1 V/50-ohms at J1 and J10.
b. A buffered 1 MHz output to A5 Digital Divider
Assembly.
c.
Rectified 100 kHz to CIRCUIT CHECK meter in
100 kHz position.
OPERATIONAL CHECK
a. Observe the CIRCUIT CHECK 100 kHz indi
cation and compare it to Table 5-3.
b.
Check for 100 kHz, 1 V rms into 50-ohms at
front and rear panel 100 kHz jacks.
c.
Check for 1 MHz, .5 V rms into 1 K-ohms at
A4(2).
d.
Check for no outputs above steps a, b, c, and d
when 5 MHz is disconnected or when 1 MHz input signal
is removed.
e. Check for 100 kHz and 1 MHz at A4 outputs
when 1 MHz input signal is reapplied.
f.
Check that the 100 kHz output at J1 and J10
meet specifications as follows:
1)
Using the 5065A 5 MHz output as an external
time base input to a counter connect the 100
kHz front-panel jack to the counter input and
check for 100 kHz ± 1 count.
Disconnect the
_
counter.
2)
Connect the front panel 100 kHz jack through a
50-ohm feedthrough to an RF voltmeter. Check
-
for 1.0 to 1.5 volts rms. Replace voltmeter with
an oscilloscope. Check the 100 kHz output for
an undistorted sine-wave.
Disconnect
the
oscilloscope.
~"
3)
To check the 100 kHz output harmonic dis
tortion, refer to Table 5-2, steps 4 and 5.
_
TROUBLESHOOTING
NOTE
For troubleshooting or tuning it will be
necessary to mount the A4 circuit card on a
HP 05065-6064 circuit
board
extender.
—
Power should be disconnected before this
assembly is removed and reinstalled.
a. Signal Checks
—
1)
To check Q1 and Q4, monitor 1 MHz at
IC1(1).
2)
To check A2, check for 1 MHz at A4(2).
3)
To check IC1, check for 100 kHz at IC1 (12).
_
4)
To Check Q6, Q8, Q9, check for 100 kHz,
1 V rms into 50-ohms at A4(11).
b. Tuning Adjustments
1)
Connect oscilloscope probe at Q1 collector.
Adjust T1 for maximum amplitide at 1 MHz.
—
"
2)
Connect oscilloscope probe at Q9 collector.
Adjust T2 for
maximum
amplitide
at 100
kHz.
3)
Make minor readjustments of T1, T2 for a
stable 100 kHz, 1 V rms into 50-ohms at —
A4(11).
MODULE REPLACEMENT
When replacing the A4 Assembly after repair or when
~
a new A4 Assembly is installed, the circuit should be
completely realigned per the preceding paragraphs.
8-26
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