6880309N62-C June, 2005
UHF Troubleshooting Tables: Troubleshooting Table for Transmitter 11-5
Poor TX range,
conducted power
OK
1. RF test jack defective Verify continuity of J140 pins 3 and 4
in RX mode only.
Replace J140.
2. Antenna matching net-
work fault
Visually 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
antenna
Verify correct antenna is installed.
Try another antenna.
Replace antenna.
No internal mic
audio (EXT MIC
audio OK)
1. Mic bias fault Verify U451-35 is low when side PTT
is pressed.
Verify Q470-6 is high when side PTT
button is pressed.
Check/replace U451.
Check/replace R474, R476, and
Q470.
2. Defective mic Verify approx 1.8V dc across car-
tridge when side PTT button is
pressed. Verify audio present (~10
mV rms) when speaking into mic.
Check mic connector and R478.
Replace mic cartridge.
3. Defective mic jack Verify continuity between J471 pins
4 and 5.
Replace J471.
No EXT MIC audio 1. Mic bias fault Verify approx 1.8V dc across EXT
MIC cartridge in TX mode. Verify
audio present (~10 mV rms) when
speaking into mic.
Check Q470. R475, R477,
L471. Check VR473, VR475,
D470 for shorts.
2. Audio path fault Verify mic audio present (~10 mV
rms) at U451-46.
Verify amplified mic audio present
(~200 mV rms) at U451-40.
Check L471, C470.
Check/replace U451.
3. Defective audio acces-
sory
Try another accessory. Replace defective accessory.
Table 11-3. Troubleshooting Table for Transmitter (Continued)
Symptom Possible Causes Procedure Corrective Action
To Next Page
Loading...
