Any suggestions from colleagues for solving this problem will be much appreciated:
I have a Toshiba 40XF355DB LCD TV with HDMI inputs, purchased circa 2008. The HDMI works fine with everything except a new recently purchased ASUS laptop PC. This includes a legacy Samsung laptop also purchased circa 2008, where the same TV can be successfully used as a second monitor etc.
The new ASAS laptop has been returned to the retailer where both it and the connecting cable being used (HDMI v1.4 & 5m long) worked immediately the PC and cable were plugged into 2 different randomly selected TVs on display in the shop. The new PC and cable therefore seem to be OK and the Toshiba TV also seems OK as it works with legacy equipment including the contemporary laptop PC.
The new ASUS laptop PC readily detects the TV correctly as "Toshiba TV".
Connecting and disconnecting the HDMI cable causes the PC to respond by changing its configuration to dual screen or internal only according to connection.
The recommended resolution selected on the PC Graphics configuration control panel is one that is shown as being supported in the TV manual (1920 x 1080p. Refresh 60Hz). Changing these to other supported settings doesn't help.
TV input is correctly set (!). PC is set to extended display on 2 monitors.
Swapping the cable to the old PC brings up the desired picture, swapping it back to the new PC leads to blue "no signal" screen on TV.
Reversing the cable end for end makes no difference - no apparent symmetry problem with cable.
It looks to me like an HDMI dialogue failure between the devices, but internet research suggests that HDMI v1.4 (if that is what the new PC meets) should be backwards compatible with v1.3 which is presumably what the TV meets.
There are many HDMI settings in the graphics control panel to fiddle with but these seem to be more to do with picture quality and colour etc. I cannot see any settings that are different on the old PC which works when compared with the new PC which doesn't.
I have also installed the latest graphics driver from Intel which made no difference.
The Toshiba TV support team state that the PC settings must be at fault however I have proved that the settings work fine on a new TV, I am not sure what to try next.
I have wondered if the the PC output is interlaced or progressive but cannot see how to choose either in the PC settings, although the TV should support either. Similarly I am not sure about the frame rates, 24 or higher, as the specifications and settings for the TV and PC are not clear and I don't know if that would matter.
The TV input compatibility table specified V. Frequency, H. Frequency and Pixel Clock Frequency but these do not seem to relate to any of the advanced Graphics settings which talk of "front porch" settings etc!
I hope that someone out there in the industry with knowledge of HDMI may be able to help me,
Many thanks in anticipation