What was found
LT VHF RECEIVES BUT UNABLE TO TRANSMIT. TROUBLESHOOTING LOG 1,VHF 1- WILL RCV BUT NO SIDE TONE OR TXMISSION FR ANY POS. DISC MIKES & 4 ACP PANELS 1 AT TIME & OVHD CALL PANEL, NO HELP. BITE ON VHF 1 OK, SWAPPING 1 & 2, NO HELP. BACK IN ORIG POS BP VHF 1 OK, GNDS AT BP CK OK. CHECKED DISC AEO307 CNTR D4927. CHECKED WIRING FROM RCVR TO D FDAU, RCVR TO D4501P, ALL CHECK OK. PTT SIGNAL AT RCVR OK. FIRST OBS AUDIO PANEL & O2 MASK DISTURBED, SYS CORRECTED ITSELF. REPLACED 1ST OBS AUDIO PANEL & O2 MASK. NR 1 VHF COMM CHKS OK. ISOLATING AUDIO SELECT PANELS FROM VHF SYS BY DISCONNECTING PLUGS D4601P, D4607P & D4603P, REF WDM 23-51-14, 23-51-21, 23-51-41, COULD NOT FIND D4611P REF 23-51-31 FOR 2ND OBS, SYS REMAINED INOP, TED AUDIO ACC UNIT, NO HELP. RPL'D NR 3 O2 MASK AND AUD PNL.