Inspiron 3520 - just out of warranty. Black screen on startup, with 7 beeps, repeated.
I understand that this beep code signifies a CPU/motherboard error - has reseating the CPU worked for anyone with this error, or is doing so pointless?
No, reseating the CPU doesn't work since the problem is with solder joints on the motherboard and requires either reflowing the solder on the affected chip or replacing the motherboard, both of which will cost more than an out-of-warranty 3520 is worth.
This is caused by a manufacturing fault so I believe you may have some recourse under the Sale of Goods Act if you are in the UK even if it is out of warranty.