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Before troubleshooting, prepare your unit as follows:
!" Turn volume control fully clockwise so that it is all the way up.
!" Install the batteries onto your unit.
Item
Symptom
1
Unit is not able to turn on.
2
No
sound
with
applied to pin 6 of IC6.
3
Squelch circuit inoperative.
4
No receiver (RX)
5
Low receiver sensitivity
6
No transmission (TX)
7
Poor or no modulation
8
Deviation of transmit frequency
TROUBLE SHOOTING
Cause/Remedy
!" Check the power voltage and power switch.
!" Check to see if regulator IC8 defective.
!" Check to see if IC1 and /or associated components is
AF
signal
Defective.
!" Check to see if speaker on control circuit VR201, IC10A,
IC10B, is defective.
!" Check to see if VR203 is defective.
!" Check to see if IC4 is defective.
!" Check to see if IC11 is defective.
!" Check to see if IC4 audio output at pin 9 is defective.
!" Check Q12.
!" Check 21.6MHz output of first mixer Q10.
!" Check 21.6MHz output of crystal filters F1, F2.
!" Check 21.6MHz output of first IF amplifier Q11.
!" Check 455kHz signal from ceramic filter F3.
!" Check to see if VCO circuit is defective.
!" Check to see MCU is defective.
!" Check to see if antenna is bad connecting.
!" Check to see if the output from Q9, Q10, Q11 and F1 F2 is
defective.
!" Check to see if the PTT switch is defective.
!" Check to see if Q13 is defective.
!" Check to see if power transmit circuit Q1, Q2, Q3 are
Defective.
!" Check to see if VCO circuit is defective.
!" Check PLL control voltage if it reads 1.2±0.3V at 156.05MHz.
!" Check to see if the microphone or MIC jack is defective.
!" Check to see if IC205 and/or its associated components are
defective.
!" Check the frequency of 12.8MHz crystal X3.
!" Adjust VC2 and verify the transmit frequency.
TEKCOM Industries Limited
Page 5 of 6
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