Ok, wellthis, you are talking about -200.
On classics, engine bleed valves are DC (DC Bus 1 and 2).
If it is true that DC dies, AC lies, now I have another doubt: will we still have presurization without APU?
It is not clear 100%, but I think STBY system won't work on battery only.
In the All Generators Inoperative section (6.20.16), the Air System equipment that will continue to work are:
. A/C pack valves
. altitude warning horn
. manual pressurization control
. Pack trip off lights
. Bleeds trip off lights
Also, from a Bus equipment list given by an engineer (not official) I see the STBY Pressurization control in under DC Bus 2 and Transfer Bus 2.
So probably what we are left with is just Manual DC control.
Btw, I would set STBY Power on BAT on final before landing, to avoid a sudden blackout at touchdown.