Behemoth build

[Higgie]

I built a Behemoth (DAM Sonic Titan) today from a PCB I bought from Haberdasher in 2010 and in the build docs it says to bias the transistor to 4.5v at the Drain via the 10k Trimpot. I subbed the 2N3819 for a 2N5457 as that's what I had on hand, observing the difference in pinouts. The lowest reading I can get is 5.85v with the trimpot at minimum.  I'm pretty sure everything is wired up correctly so this is quite puzzling. Can anyone shed some light on what could be causing this?