Hi, All
Normally when the battery is turned on you will get 4 AC and 3 DC bus off light, tie the DC bus then all three DC buses will be powered.
On tail # 74-4704 the ISO bus off light will extinguish when the battery is turned on, with out DC bus tie SW tied? The ISO off light will not press to test at this time. When the DC bus tie is tied the ESS and Main DC lights extinguish and the ISO will Press to Test. I guess this was the original operation, but was changed by a TCTO to the normal way listed above.
Does anyone know what the TCTO is that changed this or why it changed?
Thanks