Harris Platinum Z2 CD, Manual

Page: 166 / 196

6-10 888-2406-002
WARNING: Disconnect primary power prior to servicing.
Troubleshooting
This test should be used as part of a routine maintenance program at least once a
year. It should also be done if major combiner components are removed and/or
replaced, such as a Z-Plane or Isolation Board or if cabling is disconnected and re-
connected to the Z-Plane or Isolation Board.
The following tests make up the SYSTEM test:
•
PA Muting Test
•
PA ISO Resistor and Thermistor Test
•
PA RF Switch test
6.7.1.1 PA Muting Test
Each PA will be muted for 1 second, one at a time. The controller then checks the
current draw of each PA, which should be close to zero. If it finds a PA that is
drawing too much current while it is supposed to be muted it will abort the test and
report a B#_MUTE_FLT. For more information refer to PA MUTE Faults later in
this Section.
6.7.1.2 PA_ISO Resistor and Thermistor Test
If the PA Muting Test is passed, the PA_ISO resistors and thermistors will be
checked. These first two tests are actually done at the same time. With the PA
muted, the ISO resistor for that PA should increase at least 4
o
C within a few
seconds. If it does not, the test will be aborted and a B#_ISO_LOW will be reported
to the Fault Log. This could indicate one of four main possibilities.
a. The most likely problem is a defective PA RF Switch on an Isolation Board
(K1-K8). The PA RF switch could simply have bad or open contacts which
would disconnect the resistor from the PA. The PA would operate normally as
long as the system is balanced, but the resistor would not heat up when the PA
is muted. To replace the switches will require removing the associated isola-
tion board from the transmitter. See Table 4-1 on page 4-59, to cross reference
the PA number to the specific Isolation switch. For example; the test aborts
and reports B2_ISO_LOW to the fault log. Follow B2 across Table 4-1 and it
says that the Related RF Switch is K6 and the Related Isolation Resistor is
RT6 on the Isolation Board attached to the Z-Plane.
b.
The PA RF Switch could be stuck in the energized position. In this position
the ISO resistor is open and does not draw any current. However, if this is the
problem, the PA may be failed since the switch is grounding its output. A nor-
mal PA current would rule this out.
c. The ISO resistor is open which means it would not draw any current and
would not get hot. These resistors are 50 ohms @ 12W and are located on the
Isolation Boards (RT1-RT8).