351804-1 Rev. 100
COM5000-8 TECHNICAL MANUAL
c) Adjust VR1 for 1.0 VDC measured on U13 pin 8 on the Driver/Splitter/ALC PCB.
This sets the normal input drive level to the microprocessor. If more than 22 dBm is applied to the
RF input connector of the System Controller, the overdrive protection will engage.
d) Adjust VR2 for 0.55 VDC measured on U13 pin 14 on the Driver/Splitter/ALC PCB.
5.4.3.2 System Controller PCB Maintenance
To gain access to the System Controller PCB proceed as follows:
1. Remove the 4 retaining screws that secure the System Controller module to the rack cabinet. Pull the
module slowly out all the way.
2. Remove the 6 screws on the sides of the System Controller to remove the top cover.
The System Controller PCB is located as shown in figure 5.4.3A
Adjustments:
The following adjustment should be performed when a PCB assembly has been repaired or been replaced
in the field. Most of the adjustments of the System Controller require operation of the complete System.
However, a few adjustments can be performed without operating the Transmitter.
The following System Controller adjustments may be performed without operating the Transmitter:
D/A Converter U2 reference voltage adjustment:
Turn on the System Controller module. Adjust VR1 of the System Controller PCB for a voltage of 2.0 VDC
measured on U2 pin 3 (VREF).
5.4.3.3 System Controller Operational Adjustment
System Controller operational adjustment is performed to assure that the Transmitter operates within
specified limits during normal operation.
Perform adjustments only after verifying that the operational parameters measured are out of tolerance.
With the System Controller module turned OFF, verify the setting of the System Controller PCB
potentiometers listed below as follows:
Note: DO NOT PERFORM ADJUSTMENTS IF THE MEASURED VALUES ARE WITHIN THE
SPECIFIED RANGE. PRESETTING THE POTENTIOMETERS LISTED BELOW ARE REQUIRED
ONLY IF SERIOUS MIS-ADJUSTMENTS HAVE TAKEN PLACE.
The purpose of presetting the potentiometers is to avoid drastic misalignments that may
damage the equipment when power is applied.
Resistance measurements are done on the PCB removed from the chassis or in the System
Controller module with all external connections removed.
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General