Rx Rf - Motorola ASTRO XTSTM 4000 Detailed Service Manual

Troubleshooting Charts: RX RF
5.12 RX RF–Page 1
Poor RX
sensitivity or
no RX audio
Inject a standard FM test signal into the
RF Jack J1704. Use SMA Conversion
RF Adapter NNTN7153A to inject the
test signal into RF Jack. Use CPS to
ensure that attenuator feature is disabled.
Use a spectrum analyzer and
high-impedance RF probe to
measure the IF signal
VHF: between L472 and L490
UHF: before L490
Frequency OK?
VHF: 44.85 MHz
UHF: 73.35 MHz
level about
-38 dBm?
Measure RF
input level
at J1704 pin 3
RF level
-47 dBm?
Measure RF levels at C410,
compute SW_FL loss
SW_FL
loss < 2 dB?
6871620L01-C
3 kHz FM deviation,
1 kHz rate, -47 dBm
No Check
RXLO
Yes
IF
Yes
1
No
Inspect
No
about
RF Jack J1704
Yes
Check
No
SW_FL
Yes
2
Visual
No
inspection
OK?
Yes
Verify
SMA Conversion RF Adapter,
measure insertion loss
No
Loss
< 0.2 db?
Yes
Bad RF Jack.
Replace mainboard
(Jack is not
serviceable)
5-21
Replace
bad part
Replace
adapter
May 28, 2008