In Section 4.10, p135, there are some vital wires missing in the diagrams. Firstly, add the following text to the end of the first paragraph:
Before fitting C93, refit C56 to the front panel (removed on page 21). One side of C56 is fitted with a resistor R57 grounded to MSb7f&r. The two V1 & V2 grid top caps should also now be wired here. The other side of C56 goes to MSb4.
This refers to preset trimmer C56, which is adjusted by a screwdriver through a front panel hole on set up. In the original text, this trimmer, resistor R57 and the two wires for the grid top caps of V1 & V2 were completely forgotten.
Amend the Master Switch wiring schedule on p120, for wafer b front, tag 7 to:
b7 rear and ground & R57
Also on p135, there is an error in the lower diagram, the cathodes of V1 & V2 were not linked. See below for the amended diagram.