______________________________________________
HARRIS
888-9058-001
WARNING: Disconnect and lockout AC primary power prior to servicing
192
To find a problem on a quarter module, first try to locate one quarter module that is the
source of the ISO fault. With DC power off and RF drive removed, connect a scope or
meter to the ISO voltage line, and disconnect the 50 Volt wires from all but quarter
module #1 (nearest the back of the module). Cover the exposed ends of the loose 50
Volt lines with electrical tape to prevent them from shorting within the module. Close
the safety cover (applying RF drive), turn on the DC power and try to enable the
module, observing whether or not an ISO fault occurs. Shut off the DC, remove the 50
Volt connection from quarter module #1, reconnect the 50 Volt line for quarter module
#2, and again try to enable the module. Repeat with each of the remaining quarter
modules. The module should ISO fault during one of these trials (the quarter module
with the problem is the one with its 50 Volts connected when the fault occurs), and the
ISO voltage should read a low value (several tenths of a Volt or less) during the other
trials.
Once a quarter module with a problem is located, perform a careful visual inspection,
looking for burned or broken components, bad solder joints, solder splashes, loose
hardware, open circuit board traces, etc. Check the output ISO resistor (low band R15;
high band R11) by lifting one lead and measuring with an ohmmeter (should measure
190 to 210 ohms for low band, or 95 to 105 ohms for high band).
See the procedure located in section 8.5.2.3 to check for the correct ISO Fault
Threshold.
Power Supply Voltage Fault (4 blinks)
The RF FET transistors operate on a nominal
50 Volt DC supply. If the power supply voltage is too high or too low, the devices could
be damaged. The control board monitors the voltage, and reports a power supply
voltage fault if it is not between approximately 44 and 54 Volts.
If several modules exhibit the same fault, check the voltage of the power supply and
look for faulty connections. Remember that heavy current draw could cause the supply
voltage to drop significantly lower than that measured with only a voltmeter loading the
line. If only one module exhibits the fault, check the DC supply voltage and connections,
plus the module power supply pins and the wiring to its slot. If no problem is found in the
power supply or connections, then the problem could be on the control board, either in
the control logic or the comparator thresholds. See the procedure for checking for correct
Over/Under Voltage Fault Threshold located in 8.5.1.3 in this section.
Over Temperature Fault (5 blinks)
The module can be damaged if it is not cooled
properly while operating. To protect the amplifier, each quarter module has a
temperature sensing circuit that signals the control board to disable the power amplifier
if the temperature of any quarter module temperature exceeds 80
o
C. When this occurs,
the logic disables the module, and commands the red LED to blink five times.
First, check the cabinet air filters and module heatsink for accumulated dust. Verify that
the cabinet air plenum is providing proper air flow to the module slot. Measure the air