Hytera MD78X Service Manual page 549

VHF (136-174MHz 25W) Information
FGU
FGU Check
U915 (5VA) and
U918 (3V3A) work at
normal voltage?
Yes
Q104 (4V3A) works
at normal voltage?
Yes
VCO oscillates? [1]
Yes
TP124 CV voltage is
normal? [4]
Yes
TP109 feedback is
normal? [6]
Yes
X100(19.2MHz)
oscillates? [7]
Yes
Check CPU data circuit.
No
Replace U915
and U918.
No
Replace Q104.
No
Q108, Q112,
Q101 and Q105 work
normally? [2]
No
Replace Q108, Q112,
Q101 and Q105.
No
PLL U100
works normally?
[5]
Yes
Check U101, U102, R187
and R171.
No
Check the
feedback circuit.
No
Check 19.2MHz
oscillator circuit.
Yes Q106, Q110,
Q100 and Q103 work
normally? [3]
Yes
Check D107, D108, D109, D110,
D121, D122, D125 and D126.
No
Replace PLL
U100.
536
Service Manual
No
Replace Q106, Q110,
Q100 and Q103.