Motorola APX 7000 Detailed Service Manual page 138

5-34
RX RF Failure – Page 2
Remove shield,
SH3. Measure
2nd LO at
TP601 on PCB
side 1
Signal
Present?
LO Freq. OK?
700-800/VHF/UHF1/ UHF2:
Measure
CLK_SSI_RX, TP106
DIG_DATA_SSI_RX_FS, TP111
DIG_DATA_SSI_RX_DOUTA, TP112
Observe 0 to 1.875
Vdc digital signals
Levels
Measure
CLK_SSI_RX at
TP106
CLK_SSI_RX
= 1.2 MHz?
DIG_DATA_SSI_RX_FS = 20 kHz
sync pulse
DIG_DATA_SSI_RX_FS
DIG_DATA_SSI_RX_DOUTA = 16-bit I,
16-bit Q.
DIG_DATA_SSI_RX_DOUTA
Go to VOCON RX
AUDIO flowchart
Note: RF Test frequency used:
1
VHF: 154.275 MHz
UHF1: 424.975 MHz
2nd LO: 107.4 MHz
UHF2: 485.075 MHz
700: 769.0625 MHz
800: 860.0625 MHz
Measured with a high impedance probe for relative comparisons and troubleshooting only.
Actual S21 gain or loss may differ if the test point is not 50 ohms.
No
Yes
No
11
107.4 MHz
Yes
No
10
OK?
Yes
No
9
Yes
No
OK?
Yes
No
OK?
Yes
Yes
Sampling
Clock
present?
No
Check
Controller
10
10
Troubleshooting Charts: RX RF Failure
2nd LO DC bias
No
Q601-3 =
5.0 Vdc?
Yes
No
Q601-2 =
3.8 Vdc?
Yes
Remove SH8.
Inspect 2nd LO
VCO
Visual
No
examination
OK?
Yes
Replace
U602
Check Voltage
Regulator U200
Replace
Q601
Repair
Defects