Sometimes my USB keyboard stops working, all key presses are ignored and indicator LEDs turn off as well. After ~10-20 seconds it resumes working.
How can I check what is the reason - software, keyboard, motherboard, anything else?
2 Answers
The duration seems to be the device unloading and loading. There are a few "probable" causes.
1) Bad wire if moving or vibration (from the computer itself via fan's or speakers for example) can cause shorts/broken wires to lose connection. This can be from cheep wire that's not pure or stress fractures caused by excessive flexing. Most common in older devices or where a device is routinely moved from desk to lap for example in keyboards.
check: by clasping the wire in boath hands so the wire goes through them both at an angle. Move one hand down slightly and follow up with the other. If you find the part that's broken you can cut the outer casing with needle nose pliers you can find which of the internal wires is broken by lightly twisting them and solder it back together.
2) Faulty connection, usb devices while trying to be "standard" in size at times vary enough that they. This usually shows up very soon after using a device.
Check: by wiggling the connector where it connects to the computer. You can order other connectors online, or get a cable and cut off whatever is at the other end open up the keyboard and solder it in where the old cable was. This will also work for the first problem.
3) Bad power supply can cause a voltage drop on the line used by usb causing devices to seem to disconnect. This is unlikely if your mouse continues to work.
Check: This is a dangerous problem to check, I will not go into it here there are youtube tutorials and long posts on how to tear down and check a power supply.
4) Some internal device conflict IRQ or USB host routing issue. This is less likely however with every USB device you add (cameras printers modems etc) the odds of it being something like this increase.
Check: Go into device manager (in windows) and check it's settings against every other device (seriously) I have had usb keyboards conflict with sound cards.
5) Lastly and most improbable is a fault in the circuitry. Keyboard controllers are now all on a chip and very rarely from 5 to 50 dollar keyboards why the "dead key" problem is the same. This is really unlikely as the power going through is minimal and less than a 9v battery. It would however be more probable if the power supply were going bad. If the keyboard has been this way however from the start it could be a bad/cold solder joint.
check: By eliminating the first two problems, skip the 3'd connect the keyboard to another machine.
In closing I'll say keyboards are by far one of the cheapest accessories on the computer to replace. Unless it's a 50$+ gaming keyboard I'd advise replacing it for 5-20$ unless you like knowing how and why it failed, or like taking things apart for no other reason to see how it works, ignore everything and do an extra hour at work to pay for it and fix it in 5 minuets.
2I had a similar problem where my keyboard would turn off and I had to plug it out and plug it in anew to make it work again.
It turned out that the problem is in a windows power setting called "USB selective suspend" in Control Panel > Hardware and Sound > Power Options > Change Plan Settings > Change advanced power settings > USB settings
After disabling this setting my keyboard started working normally.
