How do you survive the waves of enemies while power up 3 generators?

[Oblivion Knight]

I boarded up ALL entrances. I loaded the zombie eradicator things in ALL floor spots. I can survive pretty well until I turn on the 3rd. One of those fast moving dudes with the spikey arms just tears me up. By that point all boarded walls are done. This is ridiculous! I am using the heavy assault rifle.

[Kathleen Noir]

use all tools

[tonicmole]

Remember to bring plenty of the Zombie head poppers. They are the glowing blue explosive. Forget what they're really called. They kill those boss zombies. Also map boards, and additional turrets to your quick radial menu. The first time took me a while, but once I got the hang of it I had no problems on even harder difficulties.

[Noise.]

1. Hide inside a room where there's a vending machine.
2. Buy several zombie detector ( the yellow thingy ) and "head poppers". (ALOT)
3. Mission Complete.

[DragynDance]

I bought lots of those zombie killing devices, and made sure I had lots of energy drinks since all the weight is hell on stamina. Pick up all the boards and just keep replacing the zombie killer devices as they run out and reboarding up windows as they go down. Don't board up the doorway between the big room and the small room, but board up everything else. You'll be spending most of your time defending that small room since there isn't zombie killers outside of it. Every one in a while when boards are destroyed, go outside to refresh the zombie killer devices on the outside before running back in to re-board. The assault rifle was my weapon of choice for this, I was carrying lots of ammo for it.

[Oblivion Knight]

Thanks folks....i will try all of your suggestions. Its just a pain to almost get to the end and get one shotted/k-i-a

[raistln1971]

I myself do not stay in the main building very much, I usually stay out front where the 2 eradicators are and try to kill everything to keep the eradicators from wasting too much energy and needing replacing often. I bring 3 head poppers with me just for the boss. Each round I kill the boss and then wait awhile before starting the next fan as the zombies don't appear that frequently during that time. This gives time to repair and replace eradicators, and maybe pick up some loot to sell in the machine to buy more supplies.
I would also like to note something that most people forget about, if you go do the 5th floor office before the basement, you can rack up over 20k so you can buy the things needed for the basement.

[Space Cowboy]

Collect cash and crystals from fallen zombies and use them to buy more shooty thingy modules at the vending machine and swap them out with the empty ones. This way you barely have to fire a shot. Easy as pie.

[Scud]

Like others pointed out just grind money to get both sentries and the 1 hit anti zombie grenade, is much better to waste those special grenades on the blade guys, as sentries won't be as cost effective.

[Undead Aaron]

overstock yourself with money from killing the enemies in the side room just down the hallway from the elevator control room. It is an empty room , you walk in and shoot the target and mobs of fairly easy zombies will spawn, do that a few times until you have more than enough money to full stock your guns and ammo and zombie grenades, also as many of those zombie floor zappers from the vending machine as you can. keep like 3 out in the main room at all times when 1 goes down replace it so you always have at least 2 of the 3 active. Don't bother placing them in the other rooms or outside. It's kind of a cheese way to do it, but I had so many of those Zombie Floor Lasers (cant remember their name) I just pretty much ran around replacing them and casually shooting enemies. When the PREDATOR comes if you are having trouble dodging them or surviving , just make sure you have some floor zappers down and just kite them around the control panel.