Output Assembly Ballast Load (700-1225-000) - Harris ZX2500 Technical Manual

Section 5 Maintenance and Alignments
STEP 20
STEP 21
STEP 22
STEP 23
STEP 24
5.5.9

Output Assembly Ballast Load (700-1225-000)

It is easiest to check the integrity of the RF combiner loads when the output assembly is
outside of the transmitter chassis. Visually inspect the loads for damage, and replace
any faulty components as necessary using the procedure below. In case of doubt, the
RF connection to the load may be temporarily lifted with a soldering iron and the load
resistance checked with an ohmmeter. The loads should read between 48 and 52 ohms.
Replace any load with a resistance value outside this range.
!
WARNING:
BEWARE OF HOT LOADS IF TRANSMITTER HAS BEEN OPERATING WITH ONE OR
MORE PA MODULES REMOVED.
Tools required:
# 2 star (Phillips) screwdriver
soldering iron and solder
ohmmeter
thermal compound (Wakefield 120-8 or equivalent)
razor blade or other precision straight edge
replacement load P/N 700-1225-000
STEP 1
STEP 2
STEP 3
STEP 4
STEP 5
5-38
WARNING: Disconnect primary power prior to servicing.
Close transmitter rear door and secure with hex key.
Apply AC mains power.
Press front panel ON button to turn transmitter on.
Check forward and reverse power calibrations per procedures contained
earlier in this section.
Procedure complete.
Remove screws holding combiner support frame to heatsink base.
Flip up combiner board to gain access to load (lower) board. See "Figure
5-5 Output assembly opened for servicing." on page 5-36.
Desolder tabs and remove mounting screws from damaged load.
Remove damaged RF load while observe Beryllium Oxide safety
considerations (see warning below).
Apply thin, but even, coating of thermal compound to mounting flange
of replacement load. Level with razor blade or other straight-edge as
888-2595-001
ZX Series
12/20/11