HP TM 11-6625-2779-14&P - Manual (Page 44)

Section V Model 3555B
CARRIER function, change C4. To change
the balance on VF/Nm, change the value of
A1C9.
c. To determine whether the value of these
capacitors should be increased or
decreased, lightly touch the tip and ring
banana jack insulators and watch the
direction in which the meter indication
goes. The side (tip or ring) that causes the
meter indication to decrease needs added
capacitance. The capacitance should be
changed in very small steps and checked
again.
5-24. FILTER CALIBRATION.
a.
Connect the equipment as shown in Figure
5-5 with S1 in position 1 and set the 3555B
controls as follows:
FUNCTION ................VF/Nm, 600 BAL
RANGE ....................................... 0dBm
INPUT........................... NOISE, TERM
NOISE WTG .......................3kHz FLAT
b. Connect a frequency counter to the 3555B
AC MON terminals and adjust the 654A
frequency to exactly 1.00kHz as indicated
on the frequency counter. Adjust the 654A
output level for exactly 0dBm.
c. Adjust A4R3C for 0dBm indication on the
3555B meter.
d. Change the NOISE WTG switch to 15kHz
FLAT and note the meter indication. If it
differs from the indication set up in step c,
adjust A4R3C to split the difference
between these two indications.
e. Change the 3555B NOISE WTG switch to
C MSG and adjust A4R3A for 0dBm
indication on the 3555B meter.
f. Change the 654A frequency to 3.00kHz
and adjust A4R3D for an indication of -
2.15dBm on the 3555B meter.
g. Repeat steps e and f until both points are
within specifications.
h. Change the 3555B NOISE WTG switch to
PROG and change the 654A frequency
back to 1.001Hz with the output level still
set to 0dBm. Adjust A4R3B for 0dBm
indication on the 3555B meter.
5-25. ASSEMBLY REMOVAL.
5-26. To gain access to the various assemblies in the
3555B use the following procedure.
a. Turn the set off and. remove it from the
case by removing four front panel screws.
b. Unplug the small cable on the A3
assembly.
c. Remove the two screws that secure the A3
board.
d. Gently lift up the bottom of the A3 board to
unplug it from the A1 FUNCTION
assembly.
e. Hold the bottom of the A3 board high
enough to clear the FUNCTION board and
pull the A3 assembly out. This is easily
accomplished by gently rocking the board
back and forth while pulling it down (toward
the FUNCTION board).
f. Once the A3 assembly has been removed,
the AI FUNCTION board can be removed
by pulling it out.
g. To gain access to the RANGE attenuator
(A2), Input switch and the NOISE WTG
switch, the shield must be removed. To do
this, remove the two screws on each side
of the set and lift out the shield.
h. To reassembly the set, use the reverse of
the procedure described above.
5-27. TROUBLESHOOTING PROCEDURES.
5-28. The following information is supplied to assist in
locating a malfunction in the set in a minimum of time.
It should first be determined that a malfunction does
indeed exist and that the trouble is not external to the
set.
5-29.
Before starting to troubleshoot the set, use the
front panel controls to determine exactly which function,
if any, is operating properly. Table 5-6 can aid you in
this analysis. In many cases a good front panel analysis
of the symptoms can lead you directly to the trouble.
5-30.
To simplify troubleshooting the following
information is supplied:
a. Troubleshooting Tree - - The
troubleshooting tree (Figure 5-8) is based
on the half-split method of troubleshooting
a set. The trouble can be isolated to a
general area or block using this tree. Once
the trouble has been isolated to an area, a
reference is given. to a paragraph where
more specific information can be found.
b. Functional Block Diagram - - The functional
block diagram can also be used to isolate
the trouble to block. The diagram contains
all of the essential blocks that make up the
set and includes voltage levels, test points
and adjustments. The troubleshooting tree
and functional block diagram are keyed
together by the numbers with a circle
around them. If the levels or indications in
your set do not agree with those on the
functional block diagram or troubleshooting
tree, refer to the paragraph indicated for
more detailed information.
5-10