Recommendations for Voltage Surge & Inrush Current Protection Bose Wave Radio?

Hi,

A friend recently inherited a Bose Wave Radio (No CD) and would like to kee p it forever.

I mentioned Voltage surges and possibly inrush current could kill it so was asked to research the best way to protect from these problems.

Googled and found "Understanding electronic component failure"

Also checked:

2."Inrush Current Limiter Wiki"

Then finally realized it is probably best to check with those who have repa ired Bose Wave Radios.

Did not realize how many different Bose Wave Radio (No CD) Series there are until read

Do not have it so can not compare but believe it is either Series 3 or 4. "Series 3 has 9 volt backup battery. Manufactured 1997 to 2000" "Series 4 has 9 volt backup battery. Manufactured 2000 to 2003"

Would be interested in what the difference is? Also mentioned "Each series has different PC boards with design changes. In our experience there are no big improvements between the different series radios. We repair series 1 t hough 5 radios."

In Timeline of Bose wave systems could not even find a Series 4?

Appreciate any help and recommendations!

Thanks

Ken