DP990/DP995service manual
A. PLL crystal oscillator U9 is broken. Replace it.
B. Oscillator transistor is broken. Replace it.
C.PLL chip U103 broken. Replace it.
A. Make sure the channels the both radios communicate on are of the same frequency.
B. The radios use different CTCSS/DCS signaling codes. Set the same one via PC.
C. Out of communication range.
A. Antenna in bad contact. Rescrew up antenna connector.
B. Broken LNA Q205. Replace it.
C. Squelch disabled because of too high squelch level. Set a lower level on PC.
D. Broken mixer Z201. Replace it.
E. Broken FM chip U201. Replace it.
Red light on during
transmitting, but
receiver hears no
voice
A. The power amplifier transistor outputs no power. Replace with a new amplifier.
B. The microphone does not work well. Replace with a new microphone.
Green light on during
receiving, but cannot
hear voice
A. The speaker does not work well. Replace with a new speaker.
B. The audio amplifier IC5 does not work well. Replace the IC.
C. Replace the switch diode Q9.
A. Measure the voltage at TP636 using a multimeter. It should jump from 1.2V to 2.8V.
B. Measure the voltage of the GPS module. It should be around 3.3V.
Abnormal frequency
programming
A. Check the wiring.
B. Check whether a USB driver is installed.
C. Check the contact of the earphone interface board. In case of poor contact, replace
the USB socket.
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