Had a play with this again last night.
Swapped the 100k/47k with no luck - LFO stopped working.
Removed the 150R limiting resistor - light became brighter. LFO still not working.
Swapped the 100k/47k back to where I had them (ie: in accordance with this: http://www.classicamplification.net/fv/ ... t2n_02.htm
) and voila, we have a working univibe
Still had some rotation left in the trimmer at the optimal spot. Measured my voltage at the board and I was getting 17v now so maybe I am a little low and the additional 150R was too much.
I did try the pedal at 12v(22v at the board) at is sounded relatively harsh at the revised sweet spot on the trimmer. I think the preamp is seeing too much voltage @22v.