1.) Fast Travel to
VAPL-58 Power Station (Middle of map, slightly West I believe) and go directly North (follow the power lines). After a couple of power line towers (4-5 of them), look for a small 'shack' built under one of them. Holotape is on the bookshelf facing North.
2.)Fast Travel to
Hallowed Moor Cemetery, just North of
Big Town. The Holotape is inside a church on the pulpit. *Note: Place is filled with Super Mutants.
3.)Fast Travel to
Grizzled Diner (very far East-center of map) and Holotape is on a desk behind the diner (to the left).
4.) Fast Travel to
Rockbreaker's Last Gas (near far West-center of map). The Holotape is in a shack at the very top, West side, of the tall rocky cliff. Lots of goodies in there including TWO Skill Books (one on the floor I missed). *Note: Raiders might ambush you when leaving the shack, as in my case, so arm yourself and ready to do battle once ready to leave. Also, say 'hi' to
Fluffy and
Jitters for me.
5.) Final tape is found near
Anchorage Memorial. It's on an island near there (check map) where two Centaurs spit at you. Swim to that island and deal with two Centaurs and one Super Mutant. Go past the recked 'truck' and find a tent with a captive. Free the captive and look on the table inside the tent for the final Keller Holotape.
Now, Fast Travel to
National Guard Depot located top center-North of D.C. area (area of map light in color) West of
GNR. You must search for a 'electrical switch' on the second, or third floor, of ruins. VERY DIFFICULT to locate. It's best to watch You Tube videos to aid you, but it's going to be in the far-back-left of the place after going through 'Door to Depot Training Room' and entering a second floor 'Exit' sign, and through another door labeled 'Door to National Guard Depot.' When going through that last door, switch is on the far-left wall (remember it's all ruins, thus making it difficult to locate). Once the switch is activated, go through the door with the spinning yellow warning lights (first floor, or 'basement floor' made visible with a big hole in the floor, so drop down through the hole). Enter the computer code and open the big metal doors (two of them) and be prepared to waste a Ghoul or two, and the
Experimental MIRV will be on a table to the right with FIVE Mini Nukes. *Note: Tons of robots to deal with.
I hope that helps.