Gentlemen
All you have to do is to apply the AVNCS SMOKE/SMOKE/FUMES procedure.
The GEN 1 LINE push button allows to open the generator 1 line contactor, without deenergizing the GEN 1. All the AC and DC networks remain supplied by the GEN 2 (or APU GEN if avail).
The EMER ELEC MAN ON deploys the RAT and this powers the EMER GEN. Essential buses are now powered by that GEN.
When you switch off GEN 2 (and APU GEN just in case you were using the APU) all the AC and DC networks are lost, except the essential buses, and these fuel pumps which are still fed by the GEN 1, from a line upstream of the line contactor.
Then you have shed a large part of the electrical equipments. But the fire might still be caused by one of the remaining ones...
That is why when the smoke or fumes source is not inmediately identified, what you have to do is go to the QRH procedure, push all the buttons you have to push, don the masks if you need and...
DIVERSION........INITIATE
DESCEND to FL100 MEA......INITIATE
Because you don't know how long has fate determined for the fire to become deadly nor if fate is going to give you a chance to fight the source of the fire. Maybe it is a lost battle no matter what you try.
when in doubt...
DIVERT, DIVERT, DIVERT
DESCEND, DESCEND, DESCEND