Attempting Der Eisendrache No Weapons Buys Final - BO3 Zombies

This game sucks. (2nd best BO3 map btw) A map I have played dozens of times and I can't remember almost anything without a guide. Where is that last shield part? What logical cue do I follow after pulling the lever at the test site for the DG4? It's convoluted and retarded, which is why BO3 guides have dozens of millions of views for anyone to get stuff done.