Today, it is more confusing than ever to find a fault when something does not work at all or in the way you expected. All of us have had this experience, particularly with anything that relies upon software and, sometimes, firmware. I'm not going to go to that level because there is little I can teach you to fix that. Trust me, if I could, I'd have a few lessons for Subaru. Even one of my good friends turned to me after buying a new Toyota to express his utter horror that the owner's manual is over 700 pages long. I am also going to leave out networking, routers, and the internet. That's another whole can of worms.
Let's talk about audio or video products and the human interaction. What brings this up is a recent experience where I sold a consigned piece of audio after we tested it. All seemed fine until the buyer attempted to use it. Within hours of receiving it, I received a rather terse message questioning our reputation, our ethics, and a direct threat to blast us on social media unless we took it back. Well, there was no problem in doing that but, having tested it, we wanted to resolve the apparent fault. After several emails trying to understand what was happening and making a couple of suggestions of how to test it, I said to bring it in for a refund. No problem. When the customer arrived, my staff was immediately put on the defensive with the mannerisms of the customer not even aware that there was a problem.
The problem: The remote control was not working the product. It took me a couple of minutes to get to him and upon inspecting way the remote worked, I switched it from controlling satellite to controlling audio. It worked just fine. The purchaser was silent. All was good. Meanwhile, he had purchased another unit from someplace else and wanted to return it anyway. Ok, done.
What this points out to me, is the gap between understanding a product (and even the remote control) and expectations. It was the very thing that Steve Jobs was a monster over. He understood very well what he called the intuitive approach. Sadly, most products fail miserably at this. Thus, connect a printer to an Apple system and there it is. Connect a printer to a Windows system and you have to tell the system to find a printer connected to the system. Anyway, I digress. Most systems, today, are not intuitive. So, before scaling the walls with swords and ladders, make sure you understand how the product works. There are a great number of YouTube videos out there chocked full of useful tips and guides. Heck, I just used YouTube to get my wife's phone working again and, ironically, it is an Apple. But let's move on with the simple ones.
First, have you recently lost power? Kitchen appliances like stoves and microwaves are great sources for the answer. If their clocks are flashing, you've lost power. It may have been a short burst while you were away or sleeping, maybe longer. Well, power outages have the tendency to confuse audio and video products. They may turn on but nothing seems to work. Simply unplug the unit and let it set for a few minutes. I said a few minutes and I mean it. Not 10 seconds to suit your patience at the moment. Plug it back in. Often times, this clears the problem. (Now, remember, and this is the bane of automation, if power is lost, you may also need to turn the switch back on.) This is also, by the way, a common thing to do if your internet seemingly fails. Power failures are gremlins to most modern products.
Second, is the remote control even working? An easy test for this, for those of us who own Android phones, is to simply point the remote at the camera on the phone, press any button, and see if it is flashing. If it is, the remote is transmitting IR. (Most remotes use infrared to transmit signals. This will not work if you have some sort of radio transmitter like what is used on Sony PlayStations.) If it is not flashing, replace the batteries making sure that the batteries both inserted in the right direction as well as actually making contact with the spring and tabs inside. I say this because some off brand batteries have a body that keeps the button portion of the battery from actually making contact with the tab. Try again. IR remotes will flash. Sorry iPhone owners, your camera typically will not pick up IR flashes. Solution: Borrow an Android phone or have an IR test panel handy. I carried one of those in my wallet for years.
Third, is everything mechanically connected as it should be? Sometimes, there are life's intervening events which results in things becoming unplugged. Animals, children, housekeepers, you name it. Sometimes, I swear, some people's houses are haunted. So, you may be trying to control something but it is not responding with either sound or video or maybe both. This also reminds me that sometimes it may be connected properly but to a different input or output. Thus, telling it to go to A when it is connected to B can be the issue. Sometimes, service people accidently cause a cable to fall out and they guess at where it was. Of course, I am no fan of the HDMI cable connectors as they are often loose fitting and by the shear weight of the cable, fall out. Move the TV set for a better angle, they fall out. I can hear the groans now when that happens and it falls behind a cabinet of stuff.
If all else fails, then before seeking support from your local dealer (I can not help you with foreign help center calls), map out your system as best you can, note when the problem started (and any special event) and note what has happened and what you tried to resolve the problem. This will speed up the resolution process.
I would love to share more but it's hard to cram 50 years of troubleshooting experience into single blog. It's simply not possible. And that, kiddies, is why it's important to have a local dealer.