14: Maintenance
PRC1099A-MS
14-21
1. Connect the oscilloscope to
TX OUT
and the signal generator to
1650 kHz I/O
(refer to “Mixer Board Signal Connections and
Adjustment Points” on page 14-26).
2. Connect the signal generator to
TX IN
.
3. Adjust the output level to -18 dBm at 1650 kHz.
4. While listening on a handset or headset connected to one of the front
panel Audio connectors, press PTT and speak. Listen for your voice in
the handset or headset.
Normal audio output in the handset or headset indicates the 1650 kHz
IF board is operating correctly.
Audio/Filter
Board
Perform the Synthesizer, Mixer and 1650 kHz IF board checks to verify these
boards are operating properly. The transmit audio sidetone verifies the
Audio/Filter board is operating correctly (refer to “1650 kHz IF Board” on
page 14-20).
1. Set the front panel Volume control to maximum. With the handset or
headset, check for low-level hiss.
2. Press PTT and listen for a clicking sound from the radio when the T/R
relays close.
3. Check the tone oscillator by connecting a ATF-2TONE test fixture or a
CW key device to one of the front panel Audio connectors.
4. Set the Power switch to
HI
. Measure the output power. It should
measure approximately 20W.
5. Set the Power switch to
LO
. Measure the output power. It should
measure approximately 5W.
6. Check the other Audio connector at
HI
and
LO
power settings.
The tone oscillator is used for CW and antenna tuning. If the
transmitter operates normally in the CW mode but not on voice, the
problem is with the handset or the audio connections to the board.
7. Check RF filters.
The filters switch at 3.1, 5.1, 8.0, 13 and 20 MHz. Check the filters at
2.0, 3.1, 5.1, 8.1, 13.0. and 20.0 MHz. Incorrect operation in one filter
range indicates a fault in the switching relays or the filter.
PA Board
To verify the PA board is operating correctly:
1. Connect a signal generator to
TX IN
.
2. Set the frequency to that of the transceiver (USB +1 kHz)
