Broadcast Electronics FM-5T, User Manual

Page: 71 / 191

5-10
WARNING: DISCONNECT POWER PRIOR TO SERVICING
5-72. Connect one cable between the exciter RF OUTPUT connector and the input to the RF ter
mination.
5-73. Disconnect wire No. 5 from TB1-7 on the rear of the exciter and connect a temporary wire
jumper from TB1-6 to TB1-7. Flag the temporary jumper with a piece of tape marked
TEMPORARY".
5-74. Disconnect the line cord plug and remove the fuse from the AC LINE VOLTAGE SELEC
TOR on the exciter rear panel. Cover the line cord plug with a piece of tape marked 240
VOLTS".
5-75. Remove the AC LINE VOLTAGE SELECTOR circuit board with a small pair of needle-
nose pliers and record the circuit board voltage indication . Reinsert the
circuit board so that 115/120V" is visible when the circuit board is inserted into the recep
tacle.
5-76. Replace the fuse with a slow-blow type rated at 10 Amperes.
5-77. Connect the accessory exciter line cord to the extension cord. Route the extension cord out
through the top or bottom of the cabinet to a source of 110 to 120 Vac.
5-78. Connect the accessory exciter line cord (item G) to the exciter.
WARNING
WARNING
PRIMARY TRANSMITTER POWER MUST REMAIN OFF
THROUGHOUT THE FOLLOWING PROCEDURE.
5-79. Assure that the exciter is operating independently of the transmitter.
5-80. Connect the spectrum analyzer to the RF sample port (J2) in the transmitter output trans
mission line. Adjust the analyzer to obtain a reference level display and position the ana
lyzer so that it may be viewed from the rear of the transmitter.
5-81. Note the position of the grounding stick in the rear of the cabinet.
WARNING
WARNING
USE THE GROUNDING STICK PROVIDED TO ENSURE
NO PA TUBE POTENTIALS ARE PRESENT IN THE FOL
LOWING STEP BY GROUNDING THE PA TUBE PLATE
AND SCREEN CONNECTIONS BEFORE PROCEEDING.
5-82. Open the PA cavity access door and ground the PA tube plate and screen connections to
ensure no potentials are present in the cavity before attempting to touch anything within
the cavity.
5-83. After it has been determined that no PA tube potentials are present, mark the position of
the eight neutralization adjustments, (refer to Figure 5-4). Correct neutralization will be
found near the original factory position (refer to Figure 5-4).
WARNING
WARNING
BE CAREFUL WHEN ADJUSTING THE NEUTRALIZA
TION STRAPS WITH FINGERS AS THE EDGES OF
THE MATERIAL ARE VERY SHARP.
5-84. Loosen the six screws (A, Figure 5-4) on top of each capacitor slightly--just enough to al
low adjustment of each pair of inductors. When the neutralization procedure is properly
completed, the height of all inductors will be approximately the same, within 1/16 inch
(0.16 cm).