No picture on monitor, external monitor works but with generic VGA driver

[sike_ri]

Hi,

few days ago screen on my notebook Probook 6560b  with discreete GPU 6470M went black.  Monitor does not have any backlight and also there is no picture on it (looking at angle...so it is not faulty backlight). Pulled all devices out (HDD, CD-ROM) but monitor still remains blank (no BIOS screen). On external output (VGA or DP) there is pictrure, but it can not load any Windows (I have dualboot Windows 10 and WindowsXP). In Windows 10 shows error: VIDEO_TDR_FAILURE What failed: atikmpag.sys. In Windows XP, also blue screen with error in atikmpag.sys. So, I booted in SafeMode and remove Radeon HR6470M driver and put Standard VGA driver. Now PC boots to OS, but still only on external monitor. Tried to reinstall drivers, but it always fails with blank screen and PC freeze.

With some many tries and restarts, in one moment notebook monitor starts to working again. But only up to next Windows restart.

I tried to put new HDD in it and install fresh Windows...but same thing. Booted from live linux distro...only external monitor works.

So, as I can see, external monitors on VGA or DP can work but only with generic VGA drivers. OS correctly recognize graphic card, but when driver is installed external monitor also goes blank and windows freezes (not responding on caps/num lock, no longer pingable on network).

As in one moment internal monitor went back online it seams that maybe is some bad connections...but where...GPU or video memory?

Also tried HP diagnostics...video pallete is OK but video memory test fails.

Does anyone have clue what could be a problem and how to solve it?

Thanks,

S.