[morzh]

If this is not a trimmer/padder that is under the plate (B+) voltade AND has to be accessed through a hole in the chassis, you could try to use a socket wrench, after each adjustment removing it and seeing if it changes and then adjusting it again a little to achieve the max, each time removing the wrench until the sig is peaked.
For those inside holes, with power off loosen them fist with the wrench making sure it could be moved without very strong effort, and then use the ball pen tube morfed hot after a nut of the appropriate size first.