Motorola APX 5000 Service Manual page 142

5-36
RX RF Failure – Page 2
Remove shield,
SH6A. Measure
2nd LO at
TP601 on PCB
side 1
Signal
Present?
Is the LO freq either
107.4 MHz or 111.9 MHz?
Measure
CLK_SSI_RX, TP106
DIG_DATA_SSI_RX_FS, TP111
DIG_DATA_SSI_RX_DOUTA, TP112
Observe 0 to 1.875Vdc
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: 154.275MHz
UHF1: 424.975MHz
2nd LO: 107.4 MHz
UHF2: 485.075 MHz
700: 769.0625MHz
800: 860.0625MHz
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
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 SH6B for VHF and 700/800
or SH8 for UHF1 and UHF2.
Inspect 2nd LO VCO
Visual
examination
OK?
Yes
Replace
U602
Check Voltage
Regulator U200
Replace
Q601
Repair
No
Defects