Motorola APX 3000 Detailed Service Manual page 126

5-36
RX RF Failure – Page 10
13
Check Mixer:
Remove shield, SH2. Check
the polarity of T506 and check
to see that all pins are
grounded. Visually inspect
windings.
Is the polarity
correct and all
pins are
gounded?
Yes
Remove shield, SH2.
Measure the LO power
going into the mixer,
U507, at the output side
of R525.
Is the LO power
around -3dBm?
Yes
Remove shield, SH1.
Check the polarity of T507
and check to see that all pins
are grounded. Visually
inspect windings.
Is the polarity
correct and all
pins are
gounded?
Yes
8
Remove shields, SH1 &
SH11. Measure IF level at
XTAL filter and compute
XTAL filter loss, non
ground side of C515 and
non ground side of C644.
No
Replace
T506
Check FGU
No
and replace
U507 if
needed.
No
Replace
T507
Note: RF Test frequency used:
UHF1: 424.975MHz
8
UHF2: 485.075MHz
VHF: 154.275MHz
700: 769.0625MHz
800: 860.0625MHz
Measured with a High Frequency Probe for relative comparisons and troubleshooting
only. Actual S21 gain or loss may differ if the test point is not 50 ohms.
Loss:
700: < 6dB?
No
12
800: < 6dB?
UHF1/UHF2/VHF:
<5dB?
Yes
No problem
found.
Troubleshooting Charts: RX RF Failure