Hello - and welcome!
Well, you're certainly in the right forum as you seem to have a Phantom 1. As you say, they are considered pretty 'old' now. I don't know much about the P1, but from what you have described, yes, you have a problem and the problem could be the mainboard and/or ESCs, or a problem with 3 motors (possible, but more unlikely). A very common problem is that people use motor screws which are too long, so they cause damage to the motor windings when the screws are tightened up. Or maybe someone has attempted a repair and it's been done badly - In reality, only careful, logical diagnosis of the fault will tell you.
Sadly, you may well find that the cost of repair exceeds the value of the aircraft.
Hopefully, some fellow P1 owner might be along soon to offer you more advice... However, don't forget about the useful search facility here (magnifying glass, top right) which may help you discover more about what the problem could be, while you are waiting...
Good luck!