Ac Adapters Pri & Sec ratings what can I use?
Your are right, the replacement part is not strong enough.

What you have to match is :


The input voltage must be compatible with your country (here 230-240v ~50hz )
The output voltage must be the same: (here 24v)
The output kind: DC or AC. For AC you sometime have a symbol "~" written next to the output voltage. It must be the same.
The output current must be greater or equal to the original (here 850mA)