Power Supply filter Williams vs Bally

[Just Love Pinball]

Hi all,
I bought a new mains line filter to replace on Theatre of Magic. I wrongly thought this machine was tripping my power, later found problems with my outside garden lights that I turn on when going down to the arcade. DOH! Anyway,
I took the metal can apart only to find - no filter! Just the thermistor inside that box!
Now, my Funhouse has got a line filter same as one I bought.
Question:
Is it worth as an upgrade incorporating a filter in the mains circuit on Theatre of Magic, and any other machine that doesn't have one, or leave as standard?
How comes there are filters on Williams and not Bally?

 

[pinballmania]

The filter is incorporated in the socket that you plug the mains lead into

 

[AlfonsoB]

The filter is incorporated in the socket that you plug the mains lead into

Busmans holiday?

 

[Just Love Pinball]

Thanks for that, I will check it out! Never knew that!
If I want to replace the socket filter on the rear of the machine do I purchase a whole socket assembly, individual components, or bypass those and use the new metal filter I bought as an upgrade?
Appreciate your expertise.