Service One Pa Chassis While Transmitter Is On Air (Zx7.5/Zx10); Check Balance By Disconnecting Load (Zx7.5/Zx10) - Harris ZX2500 Technical Manual

Section 5 Maintenance and Alignments
STEP 26
STEP 27
STEP 28
5.4.10 Service one PA chassis while transmitter is on air
(ZX7.5/ZX10)
Higher power ZX transmitter models are designed to be serviced without the need to
switch the transmitter off completely. Individual PA chassis can be completely shut
down and disassembled while others continue transmitting. This procedure describes
how to safely prepare an individual PA chassis for servicing while the rest of the
transmitter remains on air. It is required for any maintenance procedure involving
access to the interior rear chamber of a PA chassis. All operations executed from the
front face of the PA chassis, such as PA and PS module swaps, do not require any
special precaution and may be performed without following this procedure first.
Tools required:
Adjustable wrench
STEP 1
STEP 2
STEP 3
STEP 4
STEP 5
STEP 6

5.4.11 Check balance by disconnecting load (ZX7.5/ZX10)

A proper phase and gain balance between PA chassis is required for efficient output
combining to take place. Any imbalances result in power being directed to the 2.5 kW
5-28
WARNING: Disconnect primary power prior to servicing.
As desired, use off-air opportunity to verify reserve exciter and exciter
switchover functionality (where applicable).
Note any findings and resolutions in station maintenance log.
Procedure complete.
Remove AC mains power from PA chassis to be serviced via
corresponding circuit breakers on AC distribution chassis.
Remove RF drive coax cable from RF INPUT connector at rear of
chassis.
Using adjustable wrench, loosen retaining nut and fully insert shorting
bolt at RF output of PA chassis to be serviced to eliminate risk of back
flow of RF energy should a transmission line arc or combiner load
failure occur.
Access rear compartment of PA chassis as desired to perform
maintenance.
Reverse previous steps when finished to restore PA chassis to
operational condition.
Procedure complete.
888-2595-001
ZX Series
12/20/11