Mike wrote:
It's a Mitsubishi Diamond Plus 91 and when it is switched on, it
makes a sound like...

Tsss Tsss Tsss Tsss Tsss
Tsss Tsss Tsss Tsss Tsss
Tsss Tsss Tsss Tsss Tsss
etc.

Also, the green "on" light flashes in time with the sound. Apart
from that, it does nothing else; no picture, no nothing, zip,
nishty, nada.

I know this is probably a STUPID question, but anyone have any
idea if it's potentially repairable?

Ta,
Mike.

Sounds like an over current condition. I would check the HOT, but it
could also be many other components.