VTL MB450 Schematic

Most VTL and other push pull tube amps are loosely based on the Williamson push/pull amp circuit, if the tech is experienced he shouldn't need it.
https://www.google.com.au/search?q=Williamson+Tube+Amp+circuit&source=lnms&tbm=isch&sa=X&ved=0ahUKEwi-8oOvlsvQAhUJ-mMKHQiOCEEQ_AUICCgB&biw=1680&bih=933
Cheers George

Nice picture of cut off heads.

If the engineer can't figure out what he is looking at, you have the wrong engineer.  The circuit is straight forward tube design, each tube is independent but has a common power suppy.  You likely have a screen resistor blown from a crap tube, that is about the only thing that can go wrong.

Good luck! VTL does not give out schematics, even to authorized dealers, even on old models. When I needed to have work done on my VTL Deluxe 500 monos, my tech had to draw his own. Fortunately, he's good enough that he could.