May 28, 2008
6871620L01-C
5-16
Troubleshooting Charts:
VCO TX/RX Unlock
5.9
VCO TX/RX Unlock
VCO TX/RX
unlock
<0.6Vdc
>11.0Vdc or
drifting?
3V at C27?
Yes
Yes
Yes
No
No
No
No
No
Yes
Yes
Yes
Frequency
detected?
VCO locked?
No
Yes
No
5V at C14?
Check
VOCON Section
Check control
voltage at
Vctrl TESTPOINT
Check parts
around U1. If
OK, replace U1
Aux. line 3
high for TX
or low for RX
(VHF)?
Is unit
VHF?
Yes
Check parts
around U302.
If OK, replace
U302
Is pin 19
of VCOBIC
low for RX and
4.5V for TX?
Check parts
around Q310. If
OK, replace Q310
No
No
Yes
Yes
Aux. 3
for TX
and aux 2
for RX
(UHF)?
Is unit
UHF?
Yes
Check parts
around Q253 and
Q273.
If OK, replace
Q253 and Q273
Is Q273 = 4.5V
for TX and
Q253 = 4.5V for RX?
Check parts
around U3. If
OK, replace U3
Remove
VCO shield
Check parts
around U202. If
OK, replace U202
"Sniff"
frequency near
VCO shield
Check if VCO
is locked using
spectrum analyzer
Sniff: Using an inductive field probe
as an antenna to measure
frequency. Place the probe
approximately 1/2 inch away
from components to be sniffed.
Summary of Contents for ASTRO XTSTM 4000
Page 1: ...COLOR CHORDS 7 ASTRO XTSTM 4000 Portable Radio Detailed Service Manual ...
Page 2: ......
Page 16: ...May 28 2008 6871620L01 C xiv Commercial Warranty Notes ...
Page 22: ...May 28 2008 6871620L01 C 1 6 Introduction Notes ...
Page 26: ...May 28 2008 6871620L01 C 2 4 Radio Power Notes ...
Page 56: ...May 28 2008 6871620L01 C 3 30 Theory of Operation Notes ...
Page 100: ...May 28 2008 6871620L01 C 6 8 Troubleshooting Waveforms Notes ...
Page 194: ...May 28 2008 6871620L01 C B 2 Motorola Service Centers Notes ...
Page 204: ...May 28 2008 6871620L01 C Glossary 10 Glossary Notes ...
Page 209: ......