______________________________________________HARRIS
888-9058-001
WARNING: Disconnect and lockout AC primary power prior to servicing
158
6.4.2.2 Operational Setup and Adjustment
Vision Adjustment
STEP 1:
On the front panel of the exciter module, put the
auto/manual switch to the Manual position.
STEP 2: Turn the exciter down to 25% of its nominal
value to prevent excess drive when AGC is turned off.
STEP 3: Now switch the AGC OFF.
STEP 4:
Increase exciter power until the total transmitter
vision output power is 100%.
STEP 4: Turn AGC back on and adjust the SET control on
the module front to reduce the transmitter output vision
power to 70%.
STEP 5: Raise the exciter vision power to increase the
total transmitter output vision power to 100%.
Sound Adjustment:
Next, repeat steps 1 – 5 for the sound AGC adjustment.
6.4.2.3 Troubleshooting
a. Gain Test: when the AGC is turned off, a fixed voltage divider generates a -10
volt level that will set the voltage controlled attenuator to minimum attenuation.
Use a power meter to measure the input power, reconnect the input cable and
measure the output power. The loss should be approximately 3dB plus the value
of the fixed pad following the directional coupler. If higher, the attenuator diodes
may have changed characteristics and should be replaced with a new matched set
of four diodes.
b. No signal voltage detected at the exciter and the amplifier test points: Verify the RF
sample is present. If so, use a voltmeter to signal trace the paths to the comparator.
When working properly, the two comparator inputs should be close to the same value.
The DC voltage from the comparator output can then be traced to verify current flow
through the attenuator diodes.
To Next Page
Loading...
