Fluke 6060B Instruction Manual page 163

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OPTION INSTALLED
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HIGH- OR MEDIUM-STABILITY
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1 = TTL H i g h
0 = TTL Low
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Program the UUT to 320 MHz. If you can adjust the power supply to obtain about 320
MHz output from the VCO, the VCO and binary divider are probably OK; proceed to
paragraph 40-4 1 . If you cannot change the frequency, the problem is either the VCO, or
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the UHF binary divider, U l .
Check the signal atTP I. It should be the same as the output frequency. The level after the
buffer amplifier, Q3, Q4, at TP3 (use RF test cable) should be approximately +3 dBm.
The signal at TP 17 should be a signal sideband signal with the lower sideband component
(the desired signal) at about -20 dBm. If the only signal is the carrier frequency (same
frequency as TP3), check the quadrature generator, and the sub-synthesizer circuitry.
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The signal out of the triple-modulus pre scalar should be approximately 1 6 MHz (with
the output frequency set to approximately 320 MHz). The output of the N-Divider,
TP 14, should be approximately 1 MHz.
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As the UUT frequency is programmed, the frequency at TP 14 should change, since the
divide ratio is being changed. If the frequency is not I MHz and/ or it doesn't change, the
problem is probably with the N-Divider gate array, U 1 7, or the interface to the
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microprocessor.
If both the reference (at TP35) and the N-Divider signals at the phase detector are 1 MHz,
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the loop should lock when the operator removes the variable power supply. If the loop
does not lock, check the KNV voltage at TP37. With the Signal Generator programmed
to 320 M Hz, TP37 should be approximately 1 .0 to 2.0V. If this voltage is not correct,
check the DAC U27, latches U26 and U30, and op-amp U28. This voltage should also
change as the operator changes the Generator frequency.
lf the KN DAC appears to function, the problem is with the phase detector. Reconnect
I the variable power supply as before, and adjust the voltage for a approximately 1-MHz
signal at U44 pin 3. With this frequency slightly above
TP39 should be low.
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With this frequency slightly below
The only remaining circuitry is the loop amp U48 and the current source, U46, Q l 8, and
Ql9.
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If the loop is locked, but the 1-MHz, 10-MHz, or 100-M Hz digits cannot be programmed,
the problem is either the N-divider or the interface to the microprocessor. If the 100-kHz
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Table 40-11. Frequency Reference Control
INT/EXT
NO INT
EXT
YES INT
EXT
MHz, TP38 should be low and TP39 should be high.
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TROUBLESHOOTING ANO REPAIR
a n
RMUXOH
SHENL
0
0
1
0
1
1
0
0
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MHz, TP38 should be high and
MAINTENANCE
40-1 5