Pair of old mini b&w tvs, very retro (Brownsover CV21)

As you can see from the photo, they power up but I've been unsuccessful in getting a picture. I even tried connecting my old Playstation via the AV cables but no joy!
If you can get them working they would be nice as little "retro" TVs - you might even be able to sell them on eBAY!
Note that the built-in aerial for the Nippon has broken off and is missing.