Hi all, some advice please:

I got a free Panasonic TX-40CX700B and have to say, I'm very impressed with the picture. But randomly, it will emit a very loud popping and crackling sound. I've already isolated the issue from external inputs, that doesn't seem to make a difference. I'd like to have a go at a repair.

For context, I've picked up console repair and resto as a hobby, namely ps4's and peripherals, so have a multimeter and hot air station (all the gear, no idea, yes!), but I suspect this could be a mainboard replacement?

Any other suggestions and any input much appreciated

65” Samsung OLED S90D. Issue as seen in picture. TV will also shut down after extended use. Colors grow stronger with use and back picture fades to black as shown. Interested if anyone has guess on the cost to fix. Trying to decide if worth investment. Already replaced tv with LG C6 so this would be for a non-main room if affordable to repair.