Specifications
F.6 Troubleshooting
Troubleshooting on the RF Combiner Motherboards consists
essentially of visual inspection. Possible problem areas include:
a. Inspect connectors carefully, including removing RF Am-
plifiers if necessary to inspect pc board edge connectors.
b. Physically check connectors; plugs should be properly
inserted into jacks or sockets.
1. Connectors loose.
2. Connector damage.
NOTE
Replacement edge connector sockets will have to be soldered in
place.
c. Damage to printed circuit traces.
d. Cracked ferrite toroid cores.
1. The shield over the combiner must be removed to check
combiner transformer cores. (If transformers must be
replaced, be certain that the replacement has the same
number of turns of wire as the original).
2. Possible dirt build up around toroids and combiner pipe
after several years of operation and unfiltered air.
e. Loose taps, or incorrectly set taps on air-core inductors L1
through L16.
f. Loose connections where combiner rod sections join.
g. Failed electrolytic capacitors, used in the RC filtering in
supply voltage lines on each board.
F.7 RF Combiner Motherboard Removal
WARNING
ENSURE THAT THE TRANSMITTER IS TURNED OFF AND ALL
PRIMARY POWER IS TURNED OFF AT THE WALL DISCONNECT
SWITCH BEFORE OPENING ANY DOOR OR PANEL. BEFORE
REMOVING PANELS OR OPENING DOORS, VERIFY THAT THE
RF AMP POWER SUPPLY IS DISCHARGED BY CHECKING
“PA+VDC” ON THE FRONT PANEL MULTIMETER. USE A VOLT-
METER TO VERIFY THE POWER SUPPLIES HAVE BEEN DIS-
CHARGED PRIOR TO TOUCHING ANY COMPONENTS.
All RF Combiner Motherboards are of similar construction and
therefore will require the same basic procedure.
a. Remove all 16 RF Amplifier modules from the front.
b. Disconnect all wiring and cables from the motherboard
that is being replaced.
c. Remove all screws on the Efficiency Coil supports.
d. Remove Efficiency Coil supports.
e. Remove Efficiency Coil support standoffs (1/4" hex).
f. Remove Efficiency Coil interconnect cables from J1 and J2.
g. Use Lifting Loops to pull Efficiency Coil boards from
Motherboard. (NOTE: Try to progressively “walk” the
board from the Mothterboard to prevent damage to banana
connectors located along the board.)
h. Remove only as much of the combiner cover as necessary
from the rear of the transmitter.
CAUTION
LOCATE AND REMOVE ANY HARDWARE THAT IS DROPPED. IF
LOST HARDWARE IS REPLACED, MAKE SURE NONE OF IT HAS
LODGED ON ANY RF AMPLIFIER MODULE.
i. Remove the 2 end screws from the combiner secondary
rod.
j. Remove the motherboard fastening hardware beginning
with the two 4-40 screws in the front center card guide
support. The 4-40 screws to be removed can be identified
by the 6 inch (15cm) aluminum rods attached to the card
guide support bar.
1. Six screws on the outside right and left sides of the
motherboard.
2. Four screws on the inside top and bottom of the moth-
erboard.
k. Carefully remove the motherboard out the rear of the
transmitter.
F.8 RF Combiner Motherboard Re-
placement
Replacement of the Main Combiner/Motherboards is essentially
the reverse of the removal procedure.
a. During installation of a motherboard, it may not appear to
fit in as easily as it came out. This is due to the blue card
guides not fitting back in their slots at the same time. It is
recommended that the board be installed and just a few of
the screwsbe installedthat mount theboard to the supports.
Then from the front of the compartment, place the card
guides into their respective slots.
b. Once the motherboard has been fully mounted insert the
Allen screws that bolt the Combiner rods together in place
but do not fully tighten.
c. Loosen the two set screws that are on the fiberglass supports
on the motherboard that hold the rod in place. Now tighten
the Allen screws on the copper rod to 150 inch/lbs.
d. Retighten the set screws on the motherboard. Replace the
Combiner cover, RF Amplifier modules, and the intercon-
nection plugs.
e. Reverse of Removal Procedure.
CAUTION
REPLACE ALL COMBINER COVER SCREWS. THE MAJORITY OF
COMBINERRF GROUNDCURRENTFLOWSTHROUGHTHECOM-
BINER COVERS.
F.8.1 Adjustments
The only adjustments available are efficiency coil tap positions
and the four Binary transformer tap settings, refer to the Fre-
quency Change Procedure in Section V.
F-2 888-2339-002
WARNING: Disconnect primary power prior to servicing.