laptop doesn`t power up after usb power surge

I put a 9v adapter into a 5v external DVD drive while it was connected to my laptop via USB.

The DVD drive is "dead" (not the problem) .... but my HP EliteBook 840 G2 doesn`t power up at all.

I`ve tried powering up with just the battery.(no joy)

I`ve tried powering up with just the power adapter.(no joy)

I tried a few forums offering basic advice (press power button 15 - 30/60 seconds etc.)

This didn`t solve my issue ... so here I am ... asking the experts.

IS THERE A SOLUTION TO THIS WITHOUT GETTING OUT A SOLDERING IRON?

TIA