Digital VT420 repair?

[Waldemar Brodkorb]

Hi,                                                                                                                                                                                          
                                                                                                                                                                                             
after my Micro PDP11/83 boots up, I like to connect a Digital VT420
to the console port. This worked approx. 10 years ago. Now when I
poweron the VT420 I get no message on the screen. The f3 key doesn't
give me the configuration menu.

Is it broken? Does it have some invalid configuration in NVRAM and
can be resetted?
I tried changing brightness and contrast, no change.
Is it normal that the right LED is always on? See the picture.
https://debug.openadk.org/pdp11/vt420.jpg

I tried with and without serial connection to another system.

Thanks for any advice,
 Waldemar