June, 2005 6880309N62-C
6-6 VHF Troubleshooting Tables: Troubleshooting Table for Transmitter
No EXT MIC audio 1. Mic bias fault Verify approx 1.8 V 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 6-3. Troubleshooting Table for Transmitter (Continued)
Symptom Possible Causes Procedure Corrective Action
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