I think using a DBT with 100 watt is best. Nothing connected except an FM antenna.
Disconnect the amp boards completely before any power up.
Power up on the DBT and check all the PS voltages. Look for a really dim bulb.
Monitor the +-80v's for a time checking the set for function. Lights, tuner, switching. Maybe 30 minutes or so. If the voltage is higher than 80v's, shut it down. Fragile tuner components.
If all is good, plug in one amp at a time checking for a dim bulb. Monitor the voltages for another 30 minutes between connecting the amps.
Also, as the amps get connected the DBT bulb will ever so slightly get brighter. Not by much but you will notice a difference.
With both amps operating on the DBT check the DC Balance and a preliminary check on the idles (The idles will be close to 10mV's on the DBT. If not - you should regroup)
You could check the amp settings with one amp connected as well.
If the idles are higher than 10mV's report the voltages. I would stop and discuss with the Forum a Plan of action. Remember the outputs are gold. Protect them at all costs!
If the protection relay is clicking on, the set is in a good way.
Finely full power, checking the idles at the power setting.
Note:
The set has two relays. One is the protection, the other is a soft start relay (SS). You will hear the SS relay within a moment from flipping the power switch. Then watch the +-80v supply ramp up to the regulating voltage. When the set is operating correctly, the protection will take about 4 seconds to engage from power up.
A DBT will limit the current - a variac keeps poring the coals to it. Unless you know what the current draw is at any point on the voltage dial your asking for trouble. It takes an experienced hand on those particular sets to use a variac and amp meter.
The DBT is almost automatic and with your hand on the power switch, gives you a modicum of reaction time.
Then if all goes well: Rebuild the Power Supply. Don't waste any time.
Note:
After the set is operating with speakers you most likely will find several issues.
Channels not working. Pops in the tone control and inop function lamps. Don't get worried until you do a good Deoxit cleaning. If it was working before storage it will need a really good treatment.
That's how I would do it.