Question In what way HDMI cable is faulty?

[rickt96]

Request you all to go thru this observation and help me understand in what way cable is bad. Thanks

I have a 4 socket (individual switches type of) electrical extension board in which I plug in my Desktop PC, TV and my Satellite TV Box (STB).
My FHD TV has 2 HDMI in ports. I use it as a PC Monitor on HDMI-2 and my STB goes into HDMI-1.

When PC is on and is displaying on HDMI 2, if I power on STB from the main switch on the board, then as the STB powers on, the TV screen momentarily goes blank and comes back instantly. TV does not lose power, just display blacks for a moment.
Now I have a few HDMI cables, ones that are available for just 2 – 3 USD as well as others that are for 10 – 12 USD. The observation is that it only happens with cheaper HDMI cables. But it does not happen with cable that is available for 10 – 12 USD.

I have confirmed this after a few try-outs. Ironically there’s nothing wrong with HDMI cable otherwise. It just works perfectly. So I am trying to understand what is exactly happening here when STB powers on.
Also this issue does not occur if the STB powered on without HDMI cable. So it means as soon as it powers on it’s sending something on HDMI 1 that is causing momentary loss of signal on HDMI 2.

The issue does not occur if I give HDMI output of my Laptop not connected to mains. So I guess it may also have something to do with mains supply. I checked the earthing and there is no issue with that.

 

[Ralston18]

As I understand your post the problem may be an electrical/power brownout.

I.e. a temporary reduction in the voltage supply.

You can easily google for more information and details.

= = = =

Are you able to provide a simple sketch showing all devices and all connections between devices including the electrical extension bar? Show all outlets.

Scan the sketch and post the sketch here via imgur (www.imgur.com).

 

[Paperdoc]

There MAY be a subtle issue in the power supplied to the several units. To avoid that, it is better to have ALL units in this system plugged into a single common set of outlets such as a "power bar". This could avoid any possible issues of Hot / Neutral and Ground loops.

It is also possible that this is just the normal way that the TV responds to a change in its inputs. Some systems are designed so that they will give preference to a particular input when it powers on, just so it can conduct initialization checks to verify it can display that new input when required. But then it reverts to what WAS operating before that event. However, the fact that this does not seem to happen when one input is from the laptop. is confusing. But it is not clear whether this is laptop replacing desktop on HDMI2, or laptop replacing STB on HDMI1.