B737cl electrics

[Jimmy The Big Greek]

Lets assume that the STBY POWER SWITCH is in the off position and that TR2 fails. According to my diagrams the disconnect relay is between TR1 and TR2. So TR3 can still power TR2 even if the STBY POWER SWITCH is in the off position but not TR1. Am I right?

[Jimmy The Big Greek]

found on another more detailed schematic that there is a diod between TR3 an TR2. Why is it there?

[alexban]

my guess the diode will prevent electric flow from tr2 to tr3.
and yes,the tr2 will be backed up by tr3 ,even with transfer bus switch off.

[Jimmy The Big Greek]

ok thank you very much.