The doors are not quite as simple as they may appear. Firstly, the roundels are a different size than those in the rest of the Tardis. Actually I think for the entire history of the series the doors remained the same. So when the roundels got smaller for Tom Baker they didn’t change the doors. And for good reason: My doors are exactly 7 feet tall and the roundels in them are 24 inch (compared with 20.5 inches for the walls) and on 28 inch spacing. The door thus consists neatly of 3 roundels. If they had the smaller roundels they’d be only six foot tall and Tom Baker would bump his head on them. I've since discovered that the doors on the show were 6'6", so you could make the appropriate scaling adjustments if you want.
If the doors were their apparent shape, they wouldn’t actually open! (unless there was a large gap between them. There’s no lip on the interior of the doors and they don’t appear to be made of foam rubber, so how does this work?
Well I don’t actually know what they did for the series, but here’s my solution:
They’re actually made of MDO, like the wall panels, with a solid sheet of MDO across the middle and 2x4s making up the thickness on either side. The slightly sloping ends are clad with MDO, mitred at the corner on a table saw so that the joint doesn’t show. The resulting door looks like it was carved from a solid block of stone (MDO has no wood grain – which is good on a time machine). The inner edges of the deeper-than-usual-roundels are made from lighting diffuser panelling again.
I used three hinges per door, though I think there are actually two on the show.
And yes the big red knob on the console really does work! If you look closely at the TV show in the Tom Baker era, you see that leading up from the hinges to about level with the top of the doors is a rod, topped with a semi-circular thing. My Tardis has a similar arrangement. This is a metal rod (1/4-inch) that is anchored to the door and bends into the wall panel. Behind there is an arrangement of sash cords leading to an electric curtain/drape draw motor. This is controlled by a relay attached to the other computer hidden behind the scanner wall panel. The signal from the Big Red Knob goes into the console computer, which sends a command out through the network and actuates the digital IO system in the other computer. There’s also a motion sensor in the lobby that does the same thing, so I can get in when there’s no-one in the console room.