The MS6000 has a small lithium Battery (CR2450) inside the CPU unit. It must have 3V minimum. There are different software versions on the MS6000. Store-Sound-Store … Sound Menu: Store…
That sounds promising. Do you know where the CPU unit is? I assume it’s somewhere on the chassis of the TV? If so, do you know which board (I assume these TVs have more than one board in the back of them).
I’m quite happy to take the back of the TV off if necessary as I’ve discharged arcade monitors in the past, so quite aware of the high voltages involved.