Motorola XTL 1500, Detailed Service Manual, Page: 201 / 452

June 15, 2005 6815854H01-A
5-40 Troubleshooting Charts: Flowcharts
5.6.29 RF Power Amplifier (RFPA)—No or Low TX Power Output (380–470 MHz and
450–520 MHz)—Part 4 of 5
Specific Notes:
1. Remove C5508 and solder the center conductor of a small 50-ohm, coaxial cable to TP5502.
Solder ground to the gold shield track adjacent to TP5502. Attach an RF milliwatt meter, key
the transmitter, and measure TX_INJ power. Then, remove the coaxial cable and replace
C5508. Remove the solder added to shield track.
2. Remove R0977 in the power control section, and measure the resistance between VCNTRL
(TP5503) and ground. Replace R0977.
3. If U5501, VD1, is incorrect, inspect the bias feed circuitry (L5502 and C5505) and interstage
match components (L5503, C5509, and C5507). If U5501, RFOUT, is incorrect, inspect the
bias feed circuitry (L5505 and C5517).
4. Remove L5502 and measure the resistance between VD1 (U5501 pin 14) and ground.
Replace L5502. Remove L5505 and measure the resistance between RFOUT (U5501 pin 6)
and ground. Replace L5505.
5. Inspect C5566, C5516, C5518, and R5511-15.
6. If the Q5502 gate bias is incorrect, inspect the bias feed circuitry (R5516, L5525, C5556, and
R5527). If the bias feed circuitry is functional, then go to the Power Control—No or low
VGBIAS flowchart. If the Q5502 drain bias is incorrect, inspect the bias feed circuitry (L5508,
C5526-27, R5517, E5501, and R5574). Check U5570, Q5770, and associated circutry.
7. Remove R5516 and measure the resistance between Q5502 gate and ground. Replace
R5516.
8. Remove L5508 and measure the resistance between Q5502 drain and ground. Replace
L5508.
9. Inspect C5559-60, C5535, C5538, R5530, R5533-34, and R5536.
10. If the Q5503 pin 7 gate bias is incorrect, inspect the bias feed circuitry (R5520, C5539,
C5557, and R5525). If the gate bias feed circuitry is functional, then go to the Power
Control—No or low VGBIAS flowchart. If the Q5503 pin 6 gate bias is incorrect, inspect the
bias feed circuitry (R5521, C5540, C5558, and R5526). If the bias feed circuitry is functional,
then go to the Power Control—No or low VGBIAS flowchart. If the Q5503 pins 2 and 3
common drain bias is incorrect, inspect the bias feed circuitry (L5510, C5549-50, R5522-23,
and E5502).
11. Remove R5520 and measure the resistance between Q5503 pin 7 gate and ground. Replace
R5520. Remove R5521 and measure the resistance between Q5503 pin 6 gate and ground.
Replace R5521.
12. Remove L5510 and measure the resistance between Q5503 pins 2 and 3 drain and ground.
Replace L5510.
13. Inspect R5535, C5542-43, C5545-48, and C5551-53.
14. If the antenna switch bias voltages are incorrect, inspect R5524, L5701-4, and R5701, as well
as perform diode checks on D5701-3.
15. Inspect the remaining antenna switch parts (C5701-10).
16. Inspect L5706-8, L5712-13, C5708, C5711-14, C5719-20, R5713, and R5718.
17. Inspect D5704, R5707-8, R5702-4, and C5715-16.