Specifications

6.4 Troubleshooting Faults In The RF
Chain
If a fault occurs somewhere in the RF chain, all stages after the
faulty stage will also indicate a fault. If the fault sensing circuitry
has failed, the transmitter will still be on, with an RF Mute
applied. Begin troubleshooting at the first stage of an indicated
fault.
6.4.1
Frequency Synthesizer/Buffer Amplifier/Pre-
driver/Low Drive
If these Control front panel LEDs are all illuminated RED, this
would indicate that the drive from the Synthesizer Interface
output is low.
6.4.1.1 Selecting Synthesizer Interface B
If the transmitter is equipped with optional Synthesizer Interface
B:
a. Select B by moving S2, on the RF Interface, to the B
position or providing the correct remote control input.
b. Turn the transmitter on again. If the transmitter operates
normally the fault is on Synthesizer Interface A.
NOTE
The transmitter can be operated normally using Synthesizer In-
terface B, until time can be scheduled to continue troubleshoot-
ing Synthesizer Interface A.
c. If the fault is still present, switch back to Synthesizer
Interface A and continue.
6.4.1.2 Synthesizer Interface “A” Troubleshooting:
a. Check for +22VDC on F1, -22VDC on F2, and +8VDC
on F3 on Synthesizer Interface A. If present, then con-
tinue. If not present, troubleshoot the Low Voltage sup-
plies.
b. With an oscilloscope, monitor TP5 RF OUT on the RF
Interface board. Verify that S2 is in the A position.
1. If no RF is present, move the oscilloscope to J4-8 on
Synthesizer Interface A. A 4 to 5 Volt squarewave at
carrier frequency should be present.
2. If the waveform is not correct, troubleshoot the Syn-
thesizer Interface by turning to the Troubleshooting
section for the Synthesizer Interface.
6.4.2
Buffer Amplifier/Predriver/Low Drive
If these Control front panel LEDs are illuminated RED, this
indicates that the Buffer Amplifier output RF drive to the Pre-
driver is low.
6.4.2.1 Select Buffer Amplifier B
The transmitter is equipped with two Buffer Amplifiers. To
select B:
a. Move S1, Predriver Select Switch, on the Driver Encoder
to the B position or provide the correct control input.
(Note that the Buffer and Predriver switch together).
b. Turn the transmitter on again, and observe the Control
front panel.
6.4.2.2 Defective Buffer Amplifier A
a. If the transmitter returns with no fault, refer to the Trou-
bleshooting section for the Buffer Amplifier.
NOTE
The transmitter can be operated normally with Buffer Amplifier
B, until time can be scheduled to continue troubleshooting Buff-
er Amplifier A.
Figure 6-1. Control Front Panel
6-2 888-2339-002
WARNING: Disconnect primary power prior to servicing.