Warning: That Lucky Old Sun [spoiler alert] & SOLVED

[Jurassic Fart 1]

You're at an installation where you have the choice to restore and reroute electrical power to either Brotherhood's wishes, or to the entire grid…or overloading the power grid so that a doomsday weapon cannot be used by any faction. However, the ARCHIMIDES option, the doomsday weapon, isn't crystal-clear.

If you go inside and restore power to complete the mission, cool. But, if you want to restore the entire power grid, you either fix the generator OR you fix the maintenance robot. Do NOT fix the generator AND repair the robot; you'll overload the grid, destroying Archimides, and nobody gets power.

Edit:

The most likely answer is in the occluded spoiler text contributed by Vallence. The bot had nothing to do with the overload.

[Martin]

Bold of you to assume I would not blow the entire plant to smitherines.

[Grendalcat]

That's interesting. I don't think I have fixed both before. The robot is dormant if you try to access it after restoring power to the grid.(by fixing the generator).

[psychotron666]

You can actually get the doomsday weapon in hand held form, and it's an optional mission for the Veronica companion. But like you said it's not clear unless you're on the mission itself.

[Vallence]

I've often repaired both without this ever happening, so how you've managed to overload the grid I have no idea.

Spoiler for what routes power to what:
ARCHIMEDES II is the superweapon that the BoS wanted
Freemont & Westside is the slums on the outskirts of Vegas; a companion likes this option
Vegas Strip & McCarran is what the NCR wants power routed to
Full Region is what the Follower downstairs asked you to do (he gives you a permanent skillbook)
Full Region: Emergency Output overloads the plant, and no-one gets power.

Activating ARCHIMEDES I (a separate option to the power) kills all of the NCR outside the plant and ruins your reputation with them.

[Jurassic Fart 1]

Originally posted by Grendalcat:

That's interesting. I don't think I have fixed both before. The robot is dormant if you try to access it after restoring power to the grid.(by fixing the generator).

Well, I had repaired the generator, and then on my way to finish, I saw the robot and decided to activate him on the off chance it might be able to offer an advantage or unique dialogue option. But, no! As soon as he was powered up, he went very quickly, faster than I could run, to the generator. Should'a' shot him. I didn't learn how he'd screwed me (I had intended to restore power to the entire grid) until I went to collect my reward. That's when I was informed that NOBODY was getting any power.

I didn't like that, so I immediately loaded the last save before everything went to crap, consequently discovering that about fifteen or twenty saves had vanished, costing me almost two levels of XP (I'm making more frequent saves, and before I start that mission again, I'm going to make a backup of the saves, should they pull as Caspar on me again.).

@ Vallence: I'm doing some other side missions before retrying that mission, and have already leveled past where I was XP-wise. The irony is that after reading what you wrote, I've decided to do everything the same…except restoring the bot.

I'm going to go ahead and mark your reply as the answer, as your reputation precedes you. Even though you said that you "had no idea," I'm certain that the Follower did. This time I'm going to talk to him and not reload an earlier save, get some answers and that book.

[Jurassic Fart 1]

Just thought I'd close with the note that after running around (after reloading a save from before that) doing a bunch of other side missions, I went back and did it again. It seems that the developers hid something from the players assuming the role of the courier: While the players and the follower who wanted equity were not aware of the consequences of "restoring power to the entire grid," the courier himself, transparent to the user, was.

The courier knew that the grid couldn't handle the power. He was warned of possible problems if power was not routed as specified, but the players hearing the warning receive no certain assurance that the grid would blow. The courier's words upon reporting to the Follower scientist reveal that he knew exactly what would happen if he complied with scientist's wishes. The glasses-wearing idiot "scientist" already admitted that he was an imposter. (why is "imposter" not in Steam's dictionary?)

[Vallence]

Originally posted by Jurassic Fart 1:

Just thought I'd close with the note that after running around (after reloading a save from before that) doing a bunch of other side missions, I went back and did it again. It seems that the developers hid something from the players assuming the role of the courier: While the players and the follower who wanted equity were not aware of the consequences of "restoring power to the entire grid," the courier himself, transparent to the user, was.

The courier knew that the grid couldn't handle the power. He was warned of possible problems if power was not routed as specified, but the players hearing the warning receive no certain assurance that the grid would blow. The courier's words upon reporting to the Follower scientist reveal that he knew exactly what would happen if he complied with scientist's wishes. The glasses-wearing idiot "scientist" already admitted that he was an imposter. (why is "imposter" not in Steam's dictionary?)

Did you route it to
"Full Region" or
"Full Region (Emergency Output Level)"?
Full Region just routes the power and warns you about brownouts, Emergency Output fries the station.

[Jurassic Fart 1]

Vallence: I have to be honest. Sometimes the stuff I read doesn't sink in when I've been sitting at a keyboard too long. I don't know if it's old age and disabilities doing a number on me, or what. I looked at the post again, the one you wrote that I marked as an answer, and I'm dumbfounded.

You told me the precise options and their consequences. I didn't pay proper attention.

Well, I'm just going to live with what I did this playthrough.

Thank you for your help. After I finish this game, I'm not going right back to anopther playthrough. Another game I like, the latest in the Hitman franchise (I've played Agent 47 since he first started taking contracts) was why I came to this franchise; it was suddenly experiencing CTDs, some BS about failure to communicate between IO Interactive and nVIDIA with their updates actually reflecting GAME updates. So, by the time I finish this playthrough, that stupid problem should have been fixed. I mean, first I finished Fallout 4, then 3, and now this one has my attention.