I take it the Vdd boost mod bypasses the ferrite bead filtering the 5V supply to the Vdd regulator circuit. The bead is to keep noise out, but if the value is too high, at HIGH current demands....like mod'd Vdd setups... it wont allow enough current into the circuit fast enough to meet demand, leading to a voltage DIP at the 5V input of the Vdd regulator circuit.


What etch are we cutting now TicTac? That little 3 prone gizmo is a transistor...a discrete mosfet.... was that supplying Vref on that board? I'll have to pull the back up out again and re-evaluate the Vtt Vref connection.