The tender is identical in shape and construction to that used on the Britannia and on the 9F.  It provides four electrical pickups - a positive and negative on both the front and rear axle. The tender body is a push and click fit onto the chassis - remove it by inserting a small screwdriver into the horizontal slot where the coal hatch is. Apply pressure in a slightly downward direction and give the screwdriver a gentle twist to raise the front of the body from the chassis. The two catches at the rear can be released once the front is raised .

The side view shows the catch at the right hand side of this photo. Inserting the screwdriver pushes the catch backwards - so only insert it enough to move the plastic back by the depth of the catch. A couple of mm or so.

The weight cannot be released until the coupling screw underneath the tender is removed. A similar catch arrangement exists, and the catches on both sides have to be pressed in in order to lift the weight out. This is easy with a pair of small, thin-nosed pliers.

The positive pickups are on the right (bottom of this photo). A tag protrudes through the weight onto which is soldered the other end of the black lead from the loco. The other tag springs up slightly to make contact with the weight. The negative connectivity is through the weight, through the mounting screw and via the coupling as seen in the next photo. Note that the pickups contact the wheels on top of the flange, and that it is not possible to remove the copper contact strip without destroying the retaining melted plastic. If the copper has lost its springiness, then pop the wheels out, bend the strip down slightly and replace the wheels. This can be done without taking the tender apart.

The underside of the tender showing the coupling. The spring is not there to act as a spring. It is there to make contact with the base of the weight at one end and with the screw in the coupling at the other. 

Note the plastic insulation on the tender axles at the hub of the wheels on the right hand side of the tender (right hand side of the upside down photo). This plastic hub isolates the right side wheels from the left.  It is very important that you are aware that the wheels have to be fitted the correct way round.  Normally the left (negative) side is connected to the chassis through the axles.  So the insulation goes on the right (positive) side of the axles.

For this particular tender, it doesn't matter - as the axles are not connected to the chassis, and electrical pickup is from the top of the flange of the wheels.  But get into the habit of checking.  If. for example, you put the bogey wheels in the wrong way round, you will get a direct short across the track, the transformer will cut out and the train will not run.