9/15/06
888-2586-001
6-21
WARNING: Disconnect primary power prior to servicing.
Section 6 Troubleshooting
Platinum Z16HD+
6.10.1.2 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 temperature for that PA should increase within a few seconds. If it does not the
test will be aborted and an X#_ISO_LOW (where X can be A, B, C or D) will be
reported to the Fault Log. This could indicate one of four main possibilities.
a.
The most likely problem is a defective RF Switch on an Isolation Board (K1-K8).
The switch could simply have bad or open contacts which would disconnect the
isolation resistor from the PA. The PA would operate normally as long as the sys-
tem is balanced, but the resistor would not heat up when the PA is muted. To
replace the switches will require removing the associated isolation board from the
transmitter. See Table 4-3 on page 4-69 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 4-3 and it says that the Related RF Switch is K6 and the Related Iso-
lation Resistor is RT6 on the Isolation Board attached to Z-Plane B.
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 prob-
lem, the PA may be failed since the switch is grounding its output. A normal 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.
d.
The thermistor has come loose from the resistor. Each thermistor is attached to
the resistor with a high heat epoxy. If this has come loose the thermistor would
not heat up as it should. Check the ISO temperature of the PA reported as bad and
see if it is approximately the same as the others on that Z-Plane.
6.10.1.3 PA RF Switch Test
If it passes the previous tests, then the PA RF switches will be energized one at a time. If
it works as it should, the ISO resistor will not rise in temperature within a 2-20 second
window. At the same time the controller is also checking to see how much the system
dropped in output power to make sure the combiner is configured properly and that the
PA was working in the first place. If either part of the test indicates a problem, it will
also report an X#_ISO_SW Fault (where X can be A, B, C or D) to the Fault Log and
will abort the test. Use to locate the defective switch.
6.10.2 Hardware Test
The other option in Figure 6-4 is to test the hardware. Pressing [D] should bring up the
screen in Figure 6-6. This screen gives 3 more choices:
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