TM  11-5820-890-20-2 2-137 2.2. TROUBLESHOOTING FLOWCHARTS. Continued Chart 40 NO RT-B MODULATION FROM CREWMEMBER C 2298. (Sheet 1 of 1) Set up for multimeter as an ac voltmeter. Use the lowest range. Connect meter probes between signal line or test point and chassis ground. Key the handset and whistle into the mic. Look at the meter and note any change in the ac voltage. The change indicates the presence of the talk signal. The reading will be less than 1 volt. V U T S R P N M L K J H F E D C B A C 2298 J801, J804 V U T S R P N M L K J H F E D C B A AM 1780 J503, J505, J506, J507 NO YES OPEN ? REPLACE AM 1780. 1.   CONNECT CX 4723 TO AM 1780 J505 J507 AND CX 13300 TO J503. 2.   OBSERVE CHANGE IN AC VOLTAGE AT C 2298 J801/J804, PIN V TO PIN A (GND) (SEE NOTE). 3.   PRESS PTT AND WHISTLE SHARPLY INTO HS. 1.   REMOVE CX 13300 AT AM 1780 J503. 2.   REMOVE SUSPECT CX 4723 FROM AM 1780 J505 J507. 3.   CHECK CONTINUITY AT AM 1780 J503, PIN U TO J505 J507, PIN V. NO YES OPEN ? REPLACE CX 4723. REPLACE C 2298. 1.   REMOVE CX 4723 FROM C 2298. 2.   CHECK CONTINUITY AT C 2298 J804, PIN V TO J801, PIN V. NO YES AC VOLT CHANGE ? REPLACE C 2298. START