12/20/11
888-2595-001
6-15
WARNING: Disconnect primary power prior to servicing.
Section 6 Troubleshooting
ZX Series
Table 6-7 Output combining (ZX7.5 and higher power models only)
Symptom
Cause and Solution
2.5kW RF load hot
Load is intercepting RF power. This is normal if one PA chassis is
switched off or PA chassis output power levels are otherwise unbalanced.
If all PA chassis are switched on and indicate equal PA FWD kW power
outputs on front panel meters, check for balanced PA AMPS readings as
confirmation that forward power calibrations are trustworthy. Verify that
all original drive cables are in place and system phasing has not changed.
High reflected power
at individual PA
chassis outputs but
not at final system
output on system
metering assembly
Possible bad output combiner. Inspect output combiner for localized hot
spots or other abnormalities. Remove output combiner and open/inspect
for damage. Operate individual amplifier chassis directly into an RF
dummy load and proceed to test / check meter calibrations as if each were
a standalone transmitter.
Note:
The 2.5kW RF load may be used a dummy load for testing purposes if no
other load exists on site, but only up to its 2.5kW nominal rating !
PA chassis forward
power levels
imbalanced, different
than original test data
Possible failure of modules internal to PA amplifier chassis. Verify that
all front panel status LEDs are green and no internal faults are being
reported.
Possible failure of 3dB input attenuator inside PA chassis. Attenuators
have been seen to fail in way that allows signal through without full
attenuation. Remove SMA connection to attenuator and measure pin-to-
pin and pin-to-ground resistance with ohmmeter. Resistance should be
approx 17 ohms pin-to-pin and 150 ohms each pin-to-ground (two pins).
Replace attenuator if any of these measurements are not correct.
Possible failure of drive splitter or drive cables to PA chassis. Swap
drive cables and/or splitter outputs between PA chassis RF INPUT
connectors and operate each PA chassis one-at-a-time to determine if both
have same output power level. Do not operate both PA chassis
simultaneously with drive cables swapped because excessive power will
be directed to combiner load, possibly causing damage.
Suspect failure of splitter or drive cables if a change in power level
follows a drive cable swap.
Suspect internal failure of PA if no change in power results from a drive
cable swap.
Momentary dip in
power lasting 1-2
seconds when a PA
chassis is shut down
This is normal. Output power may temporarily dip as power control shifts
between APC circuits in different chassis.
Summary of Contents for ZX2500
Page 2: ...ii 888 2595 001 12 20 11 WARNING Disconnect primary power prior to servicing...
Page 4: ...iv 888 2595 001 12 20 11 WARNING Disconnect primary power prior to servicing...
Page 6: ...MRH 2 888 2595 001 12 20 11 WARNING Disconnect primary power prior to servicing...
Page 8: ...viii 888 2595 001 12 20 11 WARNING Disconnect primary power prior to servicing...
Page 9: ...12 20 11 888 2595 001 ix WARNING Disconnect primary power prior to servicing...
Page 10: ...x 888 2595 001 12 20 11 WARNING Disconnect primary power prior to servicing...
Page 14: ...xiv 888 2595 001 12 20 11 WARNING Disconnect primary power prior to servicing...
Page 18: ...Table of Contents Continued 4...
