Motorola ASTRO XTS 5000 - VOCON RX Audio

November 16, 2006 6881094C31-E
5-32 Troubleshooting Charts: RX RF
RX RF—Page 2
Q501-c
= 5.0 Vdc?
No
No
No
Yes
Yes
Yes
Repair
Defects
Visual
examination
OK?
Check Voltage
Regulator U1
Q501-e
= 3.7 Vdc?
No
Yes
Replace
Q501
Replace
Q502
Remove SH501 (UHF R1
& 700-800) or SH502
(VHF and UHF R2),
inspect 2nd LO VCO
Signal
Present?
Measure 2nd LO at TP501
(UHF R1 & 700-800) or
TP18 (VHF and UHF Range 2)
on PCB side 2
No
No
Yes
Yes
LO Freq.
OK?
VHF: 42.6 MHz
UHFs: 71.1 MHz
700-800:
107.4 MHz
Measure
RXCK, P1-5
RXFS, P1-6
RXDO, P1-12
Observe
0 to 3 Vdc
digital signals
Measure
bit clock rate
(Fbit) at RXCK
Levels
OK?
1
3
5
No
Yes
RXFS = 20 kHz
sync pulse
Fbit =
1.2 MHz?
4
No
Yes
No
Yes
RXFS
OK?
RXDO = 24-bit I,
24-bit Q, 8-bit
AGC. AGC varies
with RF level
Go to
VOCON RX
AUDIO flowchart
RXDO
OK?
5
5
2nd LO, 700-800: 107.4 MHz, UHF R1/R2: 71.1 MHz, VHF: 42.6 MHz, about 356 mVp
p
2nd LO DC bias
MAEPF-27471-C