Hi Andy
I have this wonderful model.
Re the pantograph there is tiny nylon wire which forces down the panto or let it do up by the force of the panto's spring.
So, NEVER EVER pull the panto up

So what can you do/
Remove the casing BUT FIRST remove the rotating plateform.
This is done by pushing out a tiny piece of brown plastic (noted 3 on the view below) above the axle to access the scezw (noted 2 on the view below)



Once the rotating platform is removed you may pull up the casing. Sometimes it may be stuck a little do not exert force but find the way up
At this stage, on a fonctionning model, the pantograph should raise by itself.
If not, then the nylon wire is tangled up
On mine the nylon was hardened and needed replacing.

Alternately, if the panto goes up freely, then it is an issue with the piezo motor
The frame and electronics look like this

Of course you may test all 3 motors and the panto one framed in red
At each powerr up, the panto will cycle to locate its position

Cheers
Jean

You must start by taking crisp pictures of the inside the casing where to nylon wire goes.
I am not near my 39970 unit so i only can tell from memory having replaced it once.

It all starts with a knot on a groved cylinder in the pantograph pick-up shoe (careful it gest lost easily)
then it goes on the loop of a spring (to keep tension but to absorb excessive force)
and last it goes on a tiny whinch that is held by one screw
It is absolute mandatory you use the same diameter of nylon wire.

You may want to look at this topic https://www.marklin-users.net/fo...agon---broken-Panto-cord

Cheers
Jean