Precision 7670 can not get to BIOS (can not boot?) after BIOS settings change

Hello,

my Precision 7670 is just 1 day old and I am very disappointed with DELL, the laptop doesn’t boot after changing BIOS settings.

I think I disabled intel turbo boost and step , Enable TXT, Disable secure boot, I think also disabled RAID and enabled AHCI instead and may be something else but don’t remember - these shouldn prevent BIOS access, or..???

I can not get to BIOS neither by F2 or F12, the screen is black, when press the power button , no Dell logo, the laptop repeatedly turns on for few second and then off (power LED and keyboard backlight switches On then off, black screen )

I have tried to clear the BIOS, CMOS and NVRAM by removing the coin-cell  RTC battery and laptop battery as per Dell service manual: Precision 7670 Service Manual | Dell UK

by draining residue power and RTC reset, disconnect RTC battery and laptop battery, waiting 10 mins, pressed power button for few second to drain any residual voltage and then power on ..... no effect same issue:

I can not get to BIOS (even with hard drive removed) it should show Dell Logo and be able go to BIOS menu but no, the laptop just starts for few seconds with black screen, then turns off and after few seconds it turns on again and repeat this forever.

I contacted the Dell support by phone and they told me because I have Ubuntu OS preinstalled I need to contact Canonical for support – well, I don’t think so, I can not get to BIOS in first place to do whatever from inside the OS, even the flashing BIOS manual says one need to have Ubuntu or Windows instlled and access BIOS update from OS or access from BIOS  by pressing press F12 at power on and go to Update…. But how when I can not access BIOS in first place.

The tech support insisted I have to contact Canonical because it is Ubuntu problem – hay, Dell support do you listen to me I can not access BIOS at all, there is no Dell Logo when power on the laptop:

 – I have even REMOVED the internal SSD drive, so no OS at all and can not be Ubuntu or Windows problem – but no, BIOS is still not accessible, so I think Dell phone support is not competent on my issue – it is not Ubuntu issue because I have removed the SSD drive so no OS at all -  it is something with the laptop and/or the BIOS  or something like that, this laptop is so expensive and Dell just ignored me.

What if I dont want to use any internal drives and OS and just want to boot from exterrnal USB, yo configure this I need access to BIOS

Any comment Dell tech support?

I will repeat again -  I CAN NOT GET TO BIOS and I have removed the SSD drive so it is not OS issue. when power on the laptop , it repetedly turns on and off in endless loop (no Dell logo on the screen - black)

Can somobody help, did someone had this problem?

(I  red in this comunity site that someone had similar issue after changing some BIOS setting but after baterry-removal he/she fixed the issue, but with me it didn't help)

Thanks for the help