In this exploded view you can see there's no way to replace a power transformer bolt without yanking the speaker and its baffle board out of the cabinet.

This unit also had a frozen Tone control.  To replace the control potentiometer, the PC board and power transformer were removed from the metal mounting plate.

We flattened the bent mounting tab on the transformer frame before reattaching it to the plate using a #8 screw, flat washer, lock washer, and nut.

To access the PC board, unsolder its orange leads (right).  They lead to the output transformer's primary coil.  The transformer's secondary coil (purple wires) can stay attached to the speaker.

You can also see the mounting holes for the Volume and Tone pots which protrude through the metal plate, the plywood speaker baffle, and the front faceplate.

The pots have long, threaded bushings and control shafts that pass through the mounting plate, the plywood baffle, and the front faceplate, still leaving enough room for the knobs.

With their large, old-school PC-mount solder pins, these pots are no longer in production.

We installed a current-production pot with the needed lengths, resistance, and taper.  We used a chassis-mount pot and hard-wired it to the PC board.

Whenever you detach and move around old sub-assemblies like this PC board, expect interconnecting wires to break away from their solder points.

It's important to keep track of where wires go before they break.

The component side of the Selmer Little Giant Mk3's printed circuit board.