The original is correct. I didn't have the manual open when I wrote the reply earlier today. It was supposed to read the Transfer bus feed the DC system.
"The AC Transfer buses supply the respective DC buses through transformer rectifier units. The DC buses cannot feed the AC Transfer buses. DC can feed the Standby AC system through an inverter but this is only after all AC is lost. Standby AC cannot feed either of the Transfer buses".
(Although DC feed to standby AC
is only through the battery, which only gets charged on the ground).
IDG and/or APU GEN to Main AC
buses to AC
Transfer Buses to DC System.
Back Up Generators to converter to AC
Transfer Bus to DC System.
If you switch off the as you claim, the left transfer bus, you have to switch off the left main generator, and BOTH Back Up Generators.
Left Transfer Bus goes to Standby AC
bus and Left TRU and C1 TRU. Right Transfer Bus goes to C2
TRU and Right TRU.
Left TRU powers Left Main DC Bus, Right TRU Powers Right Main DC Bus (they can cross tie at the Main DC bus level).
C1 and C2
powers the Captain and FO instruments respectively.
Back Up Generators power the Left, Center, and Right Power Supply Assemblies of systems, which powers the respective left, center and right flight control systems. Should that power path fail, then L PSA
gets power from Left Main DC Bus or the Hot Battery Bus, or the battery; C PSA
gets power from the Hot Battery Bus or Captain's Instrument Bus; R PSA
gets power from Right Main DC Bus or the battery.
In case people are interested...
What gets fed off the L AC
Left forward boost pump, Radio ALT L, Radio ALT C, GPS
L , ILS L, ADF L, Left Weather Radar, Left Transponder (Shed if both AC
MAIN buses unpowered), Left HF
(Shed if both AC
MAIN buses unpowered), CVR, Some cockpit lighting, MasterBright Control for cockpit panel (Normal), Overhead panel dimmer switch, Integrated Panel Dimmer switch (Normal)
What gets fed off the Standby AC
Bus (drains from battery when left transfer bus is unpowered):
R, Left VOR, ILS C, MasterBright Control for cockpit panel (Backup), Integrated Panel Dimmer switch (Backup), L Engine IGN 1 (backup for left main AC
) and fire detection, L Engine IGN 2 (backup for right main AC
) and fire detection, R Engine IGN 1 (backup for left main AC
) and fire detection, R Engine IGN 2 (backup for right main AC
) and fire detection