Update=Issue resolved repair done in a service center. 
Hi, I have a brand new Precision 7560 (XEON/512GB HDD/32GB) out of the box, ran through Windows updates as part of set up process and identified urgent BIOS update to 1.5.0 (I believe). Laptop restarted and completed Updating Firmware process (Flash Progress reach 100%) - but machine will now not boot.  Pressing power button, the power light comes on for 3 seconds then turns off. Holding down the power button results in power light staying on for 15 seconds, but turns off again. During this period the screen remains completely off. Have tried plugging in external monitor, booting with battery disconnected and using only AC power, also tried F2 and F12, as well as Boot Recovery (Ctrl + Esc) but laptop appears completely bricked.  Machine purchased through ERP and associated corporate Dell Premium subscription, but no immediate solution has been offered. Loathed to replace the machine as lead time to get shipped for this one was 8 months. Very grateful in advance for any advice. Thanks. 
Precision 7560 BIOS update bricked