May 28, 2008
6871620L01-C
5-22
Troubleshooting Charts:
RX RF
RX RF–Page 2
Q551-c
= 5.0 Vdc?
No
No
No
Yes
Yes
Yes
Repair
Defects
Visual
examination
OK?
Check Voltage
Regulator U1
Q551-e
= 3.7 Vdc?
No
Yes
Replace
Q551
Replace
Q550
Remove SH11 and
inspect 2nd LO VCO
Signal
Present?
Remove SH04 and measure
2nd LO at C560 on
PCB side 2
No
No
Yes
Yes
LO Freq.
OK?
VHF:
42.6 MHz
UHF:
71.1 MHz
Measure
RX_SSI_CLK (R1123)
RX_SSI_FSYNC (R1125)
RX_SSI_DATA (R1124)
Observe
0 to 3 Vdc
digital signals
Measure
bit clock rate (Fbit)
at RX_SSI_CLK
Levels
OK?
1
3
5
No
Yes
RX_SSI_FSYNC =
20 kHz sync pulse
Fbit =
1.2 MHz?
4
No
Yes
No
Yes
RX_SSI_FSYNC
OK?
RX_SSI_DATA =
24-bit I, 24-bit Q,
8-bit AGC. AGC
varies with RF level
Go to
VOCON RX
AUDIO flowchart
RX_SSI_DATA
OK?
5
5
2nd LO,
VHF:
42.6 MHz,
UHF:
71.1 MHz
about 356 mVpp
2nd LO DC bias
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: ......