Motorola APX 3000 Detailed Service Manual page 118

5-28
RX RF Failure – Page 2
shield, SH11.
Measure 2nd
LO at TP601
LO Freq. OK?
700-800: 107.4MHz
UHF1/UHF2: 107.4MHz
CLK_SSI_RX, output side of R618
DIG_DATA_SSI_RX_FS, output side of R616
DIG_DATA_SSI_RX_DOUTA, output side of R617
Observe 0 to 1.875
Vdc digital signals
Measure CLK_SSI_RX at
output side of R618
CLK_SSI_RX =
DIG_DATA_SSI_RX_FS = 20
kHz sync pulse
DIG_DATA_SSI_RX_F
DIG_DATA_SSI_RX_DOUTA = 16-
bit I, 16-bit Q.
DIG_DATA_SSI_RX_DOUT
Go to Controller RX
AUDIO flowchart
1
2nd LO: 107.4 MHz
Remove
No
Signal
Present?
Yes
No
11
Yes
Measure
No
Levels
10
OK?
Yes
No
9
1.2 MHz?
Yes
No
10
S OK?
Yes
No
A OK?
Yes
Note: RF Test frequency used:
UHF1: 424.975MHz
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.
Sampling Clock Yes
present? Signal side
of C620, 18MHz.
No
Check
Controller
10
Troubleshooting Charts: RX RF Failure
2nd LO DC bias
No
Check Voltage
Q601-3 =
Regulator U200
5.0 Vdc?
Yes
No
Q601-2 =
Replace
3.8 Vdc? Q601
Yes
Remove SH4.
Inspect 2nd LO
VCO
No
Visual Repair
examination Defects
Yes
Replace
U602