Fluke 6060B Instruction Manual page 163

MAINTENANCE
TROUBLESHOOTING AND
REPAIR
Table 4D-11.
Frequency Reference Control
OPTION INSTALLED
BIT
HIGH- OR MEDIUM-STABILITY INT/EXT
RMUXOK SHENL
NO
INT 0
1
EXT 0 D
YES
INT
1
1
EXT 0 0
1
=
TTL High
0
= TTL Low
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
4D^
I
,
If
you cannot change the frequency, the
problem
is
either
the
V
CO,
or
the
UHF
binary
divider,
UK
Check
the
signal at
TP
1
.
It
should be the
same
as the
output frequency
.
The
level
after
the
buffer amplifier,
Q3, Q4,
at
TP3
(use
RF
lest
cable)
should be approximately
T3 dBm.
The
signal at
TP17
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.
The
signal
out of the triple-modulus pre
scalar
should be approximately 16
MHz
(with
the
output frequency
set
to
approximately 320
MHz). The
output of
the N-Divider,
TP
14,
should be approximately
1
MHz.
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/orit
doesn't
change, the
problem
is
probably with the
N-Divider
gate array,
U17,
or the interface to the
microprocessor.
If
both
the reference
(at
TP35) and
the
N-Divider
signals at
the
phase detector are
1
M
Hz,
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
MHz, 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 U2S. This
voltage
should
also
change
as the
operator changes
the
Generator frequency.
If
the
KN
DAC
appears to function, the
problem
is
with
the phase
detector.
Reconnect
the variable
power
supply as before,
and adjust the voltage for
a approximately
1
-M Hz
signal
at
U44
pin
3.
With
this
frequency
slightly
above
1
MHz,
TP38 should be high and
TP39
should be
low.
With
this
frequency
slightly
below
1
MHz, TP38
should be
low and
TP39
should be
high.
The
only
remaining
circuitry
is
the loop
amp
U48 and the current source, U46, Q18,
and
QI9.
If
the
loop
is
locked,
but
the
1-MHz, 10-MHz,
or
100-MHz
digits
cannot be
programmed,
the
problem
is
either the N-divider or the interface to the
microprocessor.
If
the
100-kHz
4D-15