PAL Snes makes electric discharge sound (on the tv) when turning off

Audio/Video is fine while playing but when I turn the console off an electric discharge sound comes on the tv. Thats the best description I can think of at least. It starts high volume and gets lower over a couple of seconds until it disappears.

"BZZZZZZZZZZzzzzzzzzuuuum."

Got a high quality RGB scart that works fine with my two other consoles.

Also tried another ac adapter (both are Nintendo original) but no luck sadly.

Its a 1chip-02 model FRG. Looked briefly at the caps inside but didn't see any bulging/leaking caps.

Any ideas?