Motorola APX 1000 Detailed Service Manual page 787

Troubleshooting Charts: RX RF Failure
RX RF Failure – Page 2
Remove shield,
SH2. Measure
LO Freq. OK?
700-800: 107.4 MHz
VHF/UHF1/UHF2: 107.4 MHz
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 1.875Vdc
digital signals
CLK_SSI_RX at
output side of R618
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,
DIG_DATA_SSI_RX_DOUTA
Go to Controller RX
AUDIO flowchart
Note: RF Test frequency used:
VHF: 154.275MHz
UHF1: 424.975MHz
1
UHF2: 485.075MHz
2nd LO: 107.4 MHz
700: 769.0625MHz
800: 860.0625MHz
Measured with a High Frequency Probe for relative comparisons and troubleshooting only.
2nd LO at
Actual S21 gain or loss may differ if the test point is not 50 ohms.
TP601.
No
Signal
Present?
Yes
No
11
Yes
Measure
No
Levels
10
OK?
Yes
Measure
No
9
Yes
No
OK?
Yes
16-bit Q.
OK?
Yes
Sampling Clock
Yes
Present? Signal
side of C620,
18 MHz
No
Check
Controller
10
No
10
2nd LO DC bias
Check Voltage
Q601-3 = No
Regulator U200
5.0 Vdc?
Yes
No
Replace
Q601-2 =
Q601
3.8 Vdc?
Yes
Remove SH17.
Inspect 2nd LO
VCO
Visual
Repair
No
examination
Defects
Yes
Replace
U602
5-31