______________________________________________
HARRIS
888-9058-001
WARNING: Disconnect and lockout AC primary power prior to servicing
195
If this is not the case, then the cause for loss of drive could be either in the module or in
the transmitter cabinet. First, check for normal exciter and transmitter output levels.
If the exciter drive level seems normal, try the module in a different cabinet slot that is
known to have proper RF drive. If the problem doesn’t follow the module, then inspect
the cables leading to the module RF input for that transmitter slot. If the problem does
follow the module, check the RF input cable inside the module, connected between the
black power connector on the module inside rear panel and the 4-way power divider.
Module Has Full Green LED Illuminated But No RF Output:
PA modules
: Since an insufficient drive level causes one of the green LEDs to go out,
that cause is ruled out. This condition would most likely be caused by a failure of the
pass FET driving circuitry on the module control board. The control board logic has
illuminated the green enable LED, but it is not turning on the pass FETs. This will not
allow the quarter modules to receive the 50 Volts DC that they need in order to operate.
See the paragraphs on Pass FET Failure Fault (6 blinks) located on page A-22 in this
section.
Driver modules:
The pass FET driving circuitry could also be the culprit, as in PA
modules. In driver modules, however, a more likely cause is insufficient or no drive.
Try swapping driver modules, if the problem follows the module, check the module RF
path, starting with the RF input cable inside the module, then moving to the input
attenuator (R4, R5, R6) on the interconnect board, then to the first stage. Also, check
the connections between each stage and the next.
If this doesn’t isolate the problem, check the DC voltage and current supplied to each
quarter module, through the red wire connected to screw terminal TB1. Measure the
applied voltages and normal idle currents for each quarter module.
If a quarter module indicates 50 Volts present but no current, check the 15 Volts
supplied through J1-1.
If the problem stays in the same transmitter slot, the problem is within the transmitter
(AGC module, phase and gain module if present, preamp if present, power divider if
parallel drivers are used, or RF cables).
