i have a Raspberry Pi 4B 4GB RAM model and it was working fine until one day when i powered it up it started showing only a solid green light. I removed the SD card then powered it up and i got the same. I tried the same SD card with 2 different Raspberry Pi's and both booted fine, did the same with the PSU that came with the Pi. I also started noticing that the Green light is only switched on for around a minute or so and then it switches off completely (with the psu connected) . Is it safe to assume that the Pi board is dead?