Motorola Pr400 Detailed 6881096c25 B Manual

Chapter 11 UHF Troubleshooting Tables
11.1 Troubleshooting Table for Receiver
Table 11-1.  Troubleshooting Table for Receiver 
Symptom Possible Causes Procedure Corrective Action
Radio Dead (no 
turn-on beep, no 
LED indication)1. Battery dead or defec-
tive.Substitute known good battery or 
battery eliminator.Charge or replace battery.
2. Defective batery con-
tacts.Inspect battery contacts for corrosion 
or bent terminals.Clean/repair/replace J301.
3. Blown fuseCheck voltage on each side of fuse. 
If...

June, 20056881096C25-B
11-2UHF Troubleshooting Tables: Troubleshooting Table for Receiver
No Audio
1. Synthesizer out of lockVerify U201-4 is at 3V dc.Troubleshoot synthesizer/VCO 
circuits.
2. Defective IFIC Verify audio is present  at U51-8. Check Q70, Y70, U51.
3. RX audio buffer faultVerify audio is present  at U451-2.Check U510 and associated 
parts.
4. ASFIC fault Verify audio is present at U451-41. 
Verify U451-14 is high.Check squelch setting, PL/DPL 
programming. Troubleshoot/
replace U451.
5....

6881096C25-BJune, 2005
UHF Troubleshooting Tables: Troubleshooting Table for Synthesizer 11-3
11.2 Troubleshooting Table for Synthesizer
Table 11-2.  Troubleshooting Table for Synthesizer 
Symptom Possible Causes Procedure Corrective Action
Synthesizer Out of 
Lock (RX mode 
only)1. VCO faultVerify oscillator is working, check RF 
level at U251-10 per schematic.
Check dc voltages at U251 pin 2 
through 6 and 10 per 
Table 11-4.
Verify steering line voltage is 
between ~3V and 10V.
Check VCO tank...

June, 20056881096C25-B
11-4UHF Troubleshooting Tables: Troubleshooting Table for Transmitter
11.3 Troubleshooting Table for Transmitter
Table 11-3.  Troubleshooting Table for Transmitter 
Symptom Possible Causes Procedure Corrective Action
No Transmit (no TX 
LED indication)1. PTT switch defective.Verify U401-71 goes low when PTT 
is pressed.Replace PTT switch S441.
2. EXT MIC PTT fault Verify U401-72 goes low when J471-
4 is grounded.Check/replace Q470, L471 etc.
No Transmit (TX 
LED indication OK)
1....

6881096C25-BJune, 2005
UHF Troubleshooting Tables: Troubleshooting Table for Transmitter 11-5
Poor TX range, 
conducted power 
OK1. RF test jack defective Verify continuity of J140 pins 3 and 4 
in RX mode only.Replace J140.
2. Antenna matching net-
work faultVisually inspect components C140-
141, L140 or L141. Check dc conti-
nuity of L140 or L141in RX mode 
only.Repair/replace if necessary.
3. Defective or wrong 
antennaVerify correct antenna is installed. 
Try another antenna.Replace antenna.
No...

June, 20056881096C25-B
11-6UHF Troubleshooting Tables: Troubleshooting Table for Board and IC Signals
11.4 Troubleshooting Table for Board and IC Signals
Table 11-4.  Troubleshooting Table for Board and IC Signals 
IC Designator Pin Pin Function DC Voltage Comments (Condition)
U51
IFIC1RF input 44.85 MHz1.20
2 RF input decoupling 1.20
32nd LO osc output4.02
4 2nd LO osc input 4.60
5RSSI output0.74(no received signal)
6 Vcc 4.70
7Audio feedback0.89
8 Audio output 1.44 DEMOD to stage U510
9RSSI...

6881096C25-BJune, 2005
UHF Troubleshooting Tables: Troubleshooting Table for Board and IC Signals 11-7
U110
RF Power Amp
1RF input0(TX mode)
2 Vgg (gate bias) 2.65 (typ) (TX mode) (4.25V typ at VHF)
3Vdd 6.59(TX mode)
4 RF output -- Do not measure
5GroundGND
U150
Dual Opamp1 Unit 1 output 4.20 (typ) (TX mode) (5.8V typ at VHF)
2Unit 1 (-) input2.39 (typ)(TX mode)
3 Unit 1 (+) input 2.39 (typ) (TX mode)
4GroundGND
5 Unit 2 (+) input 3.30 (typ) (TX mode)
6Unit 2 (-) input3.35 (typ)(TX mode)
7 Unit 2 output...

June, 20056881096C25-B
11-8UHF Troubleshooting Tables: Troubleshooting Table for Board and IC Signals
U201
Freq Synthesizer
24Ref osc XTAL20
25 Ref osc warp output 3.00
26Superfilter cap4.48
27 Superfilter base (NU) 3.76
28Superfilter output4.52
29 NC2 0
30Superfilter input4.96
31 NC3 0
32Prescaler input1.97
33 Prescaler ground GND
34Prescaler Vdd2.99
35 Prescaler Vref (NU) 1.97
36Digital Vdd2.99
37 TEST1 (NU) 0.01
38TEST2 (NU)0
39 Bias 2 3.38 (typ) (1.34V in TX mode)
40Bias 11.50 (typ)(3.20V in TX...

6881096C25-BJune, 2005
UHF Troubleshooting Tables: Troubleshooting Table for Board and IC Signals 11-9
U251
VCO / Buffer
12Prescaler output2.26
13 TX switch output (NU) 0.06
14Vcc_BUFFERS3.00
15 TX VCO emitter 0 (RX mode)
16TX VCO base0(RX mode)
17 GND_LOGIC GND
18Vcc_LOGIC3.00
19 TRB input 0.03 From U201-2 (RX mode)
20FLIP inputGND
U310
5V Regulator1 Vin 7.48
2GroundGND
3 Control input 7.48
4Bypass capacitor1.26
5Vout 4.96
U320
3.3V Regulator
1GroundGND
2 Feedback 1.23
3Ta p  ( N U )0
4 Vin 7.48
5Vo u...

June, 20056881096C25-B
11-10UHF Troubleshooting Tables: Troubleshooting Table for Board and IC Signals
U401
Microprocessor
10PB1_ADDR93.05
11 PB2_ADDR10 0.16
12VDD3.23
13 VSS GND
14PBO_ADDR83.05
15 PB5_ADDR13 0.13
16PG1_XA140.20
17 PG4_XA17 3.17
18PG5_XA180
19 PG3_XA16 3.21
20PG2_XA150.30
21 PB4_ADDR12 0.22
22PF7_ADDR73.03
23 PF6_ADDR6 3.08
24PF5_ADDR53.06
25 PF4_ADDR4 0.16
26PF3_ADDR30.26
27 PF2_ADDR2 3.06
28PF1_ADDR13.06
29 PFO_ADDR0 3.05
30PC0_DATA00.69
31 PC1_DATA1 0.96
32PC2_DATA21.10
33 PC3_DATA3...