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then the fault lies in the power on circuit of the transceiver. To test, ground the abovementioned junction
and the transceiver should start up.
If however the above mentioned junction is near zero volts, the fault is likely to lie in the power supply
circuit. Check both sides of thermal fuses F1 and F2. If the power supply is OK then there is likely to be a
problem on the microprocessor board and that board should be exchanged. A short on the power supply
will cause one or both of the abovementioned thermal fuses to get quite hot to the touch and will result in no
or low voltage on the output side whilst the input side will have normal voltage (12 to 14V).
After power up the “Barrett logo” screen stays on.
This indicates that there is no communication between the microprocessor board and the front panel. The
Microprocessor board should be exchanged.
Transceiver will not receive but displays OK
It is assumed in this section that, the transceiver turns on and displays are normal.
No receiver noise
-
Check the speaker is plugged in. or that the speaker / microphone is connected.
-
Check that the audio mute, selcall mute or signal strength mute is switched off.
- Check audio path from the audio power amplifier back to the DSP DAC output by injecting a low level
audio signal to the junction of R21 andR22 on the microprocessor PCB.
-
Check audio path from the product detector to the DSP input. Inject a low level (<100mV) audio signal
into pin 3 of the product detectors amplifier U57. If the signal is not heard then the problem lies in the
DSP unit. The board should be exchanged.
Receiver noise present, but does not receive
-
Tune the receiver to a low frequency around 4 MHz , touch the antenna input with a short piece of
wire or a screwdriver. Clicks and extra noise should be heard in the loud speaker.
-
If no clicks are heard, the next steps assume audio injection can be heard back to pin 3 of U57,
(see
above).
-
Set mode to upper sideband.
-
Check that the carrier injection oscillator is present on TP4 of the microprocessor PCB. If not
present the fault is likely in the microprocessor U1. The microprocessor PCB should be exchanged.
-
Check the second local oscillator LO2 is present on TP21. If not present the fault is likely in the
microprocessor U1. The microprocessor PCB should be exchanged.
-
Check the first local oscillator LO1is present at TP8. If possible, also check that its frequency is
correct. If not present the fault is likely in either VCO and phase locked loop area or there is a
problem with the DDFS reference on TP3.
-
Check that there is noise (with no antenna connection) from the 455 kHz IF amplifier with a CRO.
The level should be about 500mV P-P. The presence of noise indicates that the 455 kHz amplifier is
working.
-
If the above tests all prove to be O.K. then the problem most likely is in the front end of the receiver.
Further testing will require specialised equipment and should not be attempted in the field. The
microprocessor PCB should be exchanged.
