Motorola ASTRO XTSTM 4000, Detailed Service Manual

Page: 83 / 210

6871620L01-C May 28, 2008
Troubleshooting Charts: RX RF 5-21
5.12 RX RF–Page 1
Frequency OK?
VHF: 44.85 MHz
UHF: 73.35 MHz
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
No
No
Yes
Yes
Poor RX
sensitivity or
no RX audio
Check
RXLO
Replace
bad part
Verify
SMA Conversion RF Adapter,
measure insertion loss
Visual
inspection
OK?
No
Yes
Bad RF Jack.
Replace mainboard
(Jack is not
serviceable)
Loss
< 0.2 db?
Replace
adapter
No
Yes
Inspect
RF Jack J1704
Measure RF
input level
at J1704 pin 3
Measure RF levels at C410,
compute SW_FL loss
RF level
about
-47 dBm?
No
Yes
SW_FL
loss < 2 dB?
Check
SW_FL
Yes
No
IF
level about
-38 dBm?
1
2
3 kHz FM deviation,
1 kHz rate, -47 dBm