This photo shows the Ampeg SVT-VR power amp chassis fully removed from its case.

If you haven't already, pull out all the glass electron tubes (valves) from their sockets.

There are six, large, type 6550 power tubes.  This photo shows how the six tubes are split into two groups of three.

One group amplifies the positive portion of the input signal while the other group amplifies the negative portion.  This design is called push-pull or complementary symmetry.

There are also three miniature tubes you must remove.  Two are 12AU7 types and one is a 12AX7.  The tube locations are indicated on the amp's rear panel.

The "Tube Board" is the PC board that contains most of the amplifier's output stage.

The Tube Board is attached to the underside of a metal plate which is held down by the three screws circled in this photo.

Take out these three screws to lift up the plate assembly.

Here you see the Tube Board attached to the underside of the metal plate.  The PC Board connects to the rest of the amp via five wires and a 7-pin cable.

You must unplug these connections before removing the loosened plate assembly.

The 7-pin cable connector (lower right) pulls straight off of its circuit pins.  Take note of which way it connects so you can reinstall it with all wires going to the correct pins.

In the opposite corner of the board, unplug the blue wire, the blue/white wire, and the brown wire (right).

Each wire has an insulated, quick-disconnect flag.  In this photo, one of the flags is disconnected from its spade lug.

The circuit board is labeled to show which color wire goes to which lug.

The blue wire and the blue/white wire feed the 6550 plates — the blue wire feeds one trio and the blue/white wire feeds the other trio.

The brown wire feeds all six of the 6550 screen grids.

Then, near the center of the board, unplug these two white wires which also use quick-disconnect flags.

These two wires carry the AC filament voltage for the 6550 tubes.  Either wire can go to either lug.