GOOGLE Nest Hello Doorbell works on USB but not on adapter power

[SimonHF]

So I have 3 of these doorbells and 3 other google cameras in my home. All work perfectly as these one did. But it suddenly stopped working recently. I bought this identical adapter to see if it is the power supply or the Google Nest Hello doorbell.

On the old power supply then nothing happens -- no lights etc -- and the power supply is cold too the touch. On the brand new power supply, also nothing happens, but the power supply gets very hot, relatively fast in a few minutes.

However, if I plug in the USB power then the device just works as normal.

So what gives? Has something broken in the doorbell so it will not work without USB power any longer? Any body else experienced something like this? How to move forwards? Thanks!

[EmptyNester]

I have a guess as to what is happening. The nest HELLO door bell was designed with a small rechargeable battery inside for a few reasons.  But once that battery gets to be in the 3-5 year range they fail.   Typically the first sign that shows up is when the button is hit to ring the doorbell it goes offline for a few minutes.   Unfortunately this battery is not user replaceable and it pretty much ends the life of the doorbell.