Broadcast Electronics AM-2.5E, User Manual, Page: 249 / 320

WARNING: DISCONNECT POWER PRIOR TO SERVICING
2-6
WARNING
WARNING
DISCONNECT ALL TRANSMITTER PRIMARY POWER
BEFORE PROCEEDING.
2-56. Disconnect all transmitter primary power.
2-57. Remove all test equipment and replace the exciter circuit board.
2-58.
DISPLAY CIRCUIT BOARD ADJUSTMENTS.
2-59.
L/L+R AND R/L-R DISPLAY CALIBRATION CONTROL.
L/L+R calibration control R42
and R/L-R calibration control R48 calibrate the L/L+R and R/L-R displays. The L/L+R
and R/L-R calibration controls are adjusted in the following procedure.
2-60. Procedure. To adjust L/L+R calibration control R42 and R/L-R calibration control R48,
proceed as follows:
WARNING
WARNING
DISCONNECT ALL TRANSMITTER PRIMARY POWER
BEFORE PROCEEDING.
2-61. Disconnect all transmitter primary power.
2-62. Connect the audio generator to the TB2 LEFT INPUT and RIGHT INPUT audio
terminals on the ECU rear-panel. Operate the transmitter at a normal output power and
the EXCITER MONITOR for L+R/L-R indications.
2-63. Adjust the audio generator for an in-phase L=R 1 kHz output at a level to generate 100%
modulation as indicated by the modulation monitor. Adjust L/L+R calibration control R42
until the EXCITER MONITOR just indicates 100% L+R modulation.
2-64. Adjust the audio generator for an out-of-phase L=R 1 kHz output at a level to generate
100% L-R modulation as indicated by the modulation monitor. Adjust R/L-R calibration
control R48 until the EXCITER MONITOR just indicates 100% L-R modulation.
WARNING
WARNING
DISCONNECT ALL TRANSMITTER PRIMARY POWER
BEFORE PROCEEDING.
2-65. Disconnect all transmitter primary power and remove all test equipment.
2-66.
TROUBLESHOOTING.
WARNING
WARNING
WARNING
WARNING
THE TRANSMITTER CONTAINS MULTIPLE CIRCUIT
GROUNDS WITH HIGH AC AND DC POTENTIALS
WITH RESPECT TO THE CABINET WHICH IS AT
EARTH POTENTIAL. DO NOT ENERGIZE THE
TRANSMITTER WITH TEST EQUIPMENT CON
NECTED TO THE TRANSMITTER OUTPUT
NETWORK, RF POWER MODULE, RF COMBINER, OR
POWER SUPPLY COMPONENTS.
2-67.
SAFETY CONSIDERATIONS.
The AM-2.5E/AM-5E transmitters are equipped with
extensive indicator and meter circuitry to allow the operator to isolate problems to a
specific area within the transmitter. Due to the hazardous voltages and currents
contained in the equipment, operation of the transmitter with test equipment connected
to transmitter output network, RF power module, RF combiner, or power supply
components is extremely dangerous and must not be attempted. Test equipment may be
connected to the ECU circuit boards from the front of the transmitter using the supplied
extender circuit board with power energized. Therefore, the transmitter indicators and
meters must be used to isolate a problem to a specific area. The maintenance procedures
presented in this section should be performed only by trained and experienced
maintenance personnel.