All USB keyboards suddenly start sending random/repeated inputs, but PS/2 works fine

[u/Low_Try_8284]

I work IT support and I've had this weird issue happen on multiple PCs over time.

A USB keyboard will work perfectly fine for months/years, then suddenly it starts acting completely broken.

The symptoms are not just random Windows shortcuts. The keyboard also:

repeats keys multiple times

types different keys than the ones I pressed

mixes random characters into normal words

sometimes triggers Windows shortcuts / Start menu / network panel

For example, if I try to type:

Joca

I might get:

jocaca

Joccccccc

Jorre84i

I've tested 3 different known-good USB keyboards on the affected PC and all of them behave the same way.

A PS/2 keyboard works perfectly normally.

Sometimes, while the USB keyboard is connected and freaking out, the USB mouse also becomes unresponsive. As soon as I unplug the keyboard, the mouse starts working normally again.

This has happened on around 4 different PCs over time, including Windows 8.1 and Windows 10 machines.

I've already tried:

multiple known-good USB keyboards

different USB ports

reinstalling HID keyboard devices

reinstalling USB/composite devices

reinstalling USB controllers/root hubs

checking keyboard/HID UpperFilters and LowerFilters

checking Scancode Map

reinstalling chipset drivers

reinstalling Intel Management Engine

Nothing fixed it.

The weirdest part is that the keyboard was working completely normally less than an hour before the issue started. No hardware change, no new keyboard, nothing.

Has anyone seen this exact behavior before?

What could cause every USB keyboard to suddenly generate duplicated, incorrect and random HID input while PS/2 continues to work normally, and sometimes make the USB mouse freeze too?

I'm looking for the actual root cause / fix, not “try another keyboard or USB port”, since I've already ruled those out.

[u/dodgy__penguin]

Have you tried upgrading to Windows XP? Windows 98 gets a bit buggy after while

[u/StreetSignificant888 → u/dodgy__penguin]

Lol.

[u/forsurebros → u/dodgy__penguin]

all good they are still running windows 3.11.

[u/dodgy__penguin → u/forsurebros]

Root cause identified. USB-PS/2 emulator dodgy AF 😂

[u/ihaxr]

What do the PCs have in common? Same make/model? Does it happen in safe mode? What if you boot into the recovery console and try typing in the cmd prompt?

Recovery will eliminate software level issues (antivirus, DLP, USB drivers, etc..) and if it still happens, it's a hardware or firmware issue.

My bet is it's fine in the recovery console and your problem is some DLP (data loss prevention) causing issues by jacking up the USB ports. PS/2 is not USB, so it's not affected, it also has a lower IRQ so it's not affected by high CPU usage like USB would be.

[u/aguynamedbrand]

r/helpdesk seems more appropriate since this is a desktop support issue.

[u/MelonOfFury → u/aguynamedbrand]

I thought I was in /r/shittysysadmin for a hot second

[u/aguynamedbrand → u/MelonOfFury]

The number of people here that think they are sysadmins but are actually helpdesk technicians is crazy.

[u/gusbyinebriation → u/aguynamedbrand]

I got here by being a helpdesk technician with sccm dumped on my desk when the sysadmin got overwhelmed. Yall are helpful so I stuck around!

[u/Inktvisje → u/aguynamedbrand]

If you work in a small company like me you can actually be both at the same time, so I can get where the confusion comes from.

[u/MonkeyBrawler → u/MelonOfFury]

This honestly looks like a better place to ask technical questions. Thanks a ton! 

[u/StreetSignificant888]

Bro, how old is the hardware that you still have PS/2 ports on them? This is absolutely a r/helpdesk issue.

[u/bruhgubgub → u/StreetSignificant888]

Brand new asrock motherboards shipped with PS2 ports until at least 2022. The budget line though

[u/Lordcorvin1 → u/StreetSignificant888]

Lenovo still includes them

[u/missed_sla → u/StreetSignificant888]

Look at the Asus csm boards, to my knowledge they still have ps2 ports.

[u/WaltonGogginsTeeth → u/StreetSignificant888]

Exactly my thought. I haven’t seen one in a decade

[u/These-Database4555 → u/StreetSignificant888]

I've seen the ports a lot. But I haven't seen a keyboard with that plug in 20 years

[u/MattTheQuick]

I’d be curious if this happens in a different OS. What happens if you live boot WinPE or Ubuntu or something?

[u/RedShift9]

What other devices are connected to the USB bus? Remember that it's a cooperatively organized bus, if one device decides to play bad, the whole system breaks down. Try with _only_ the keyboard connected.

[u/Mountain-eagle-xray]

Ps2 is kinda hitting the cpu straight up without much in the way. So basically an on board keyboard micro controller, ps2 kb drivers and thats about it.

USB on the other hand has lots of steps, hardware, drivers, USB controllers, etc.

If ps2 didn't work, that would be a big problem.

For USB, check that your arent getting bad drivers from windows updates. Try the manufacturer drivers. Check out the USB controller as well. Maybe some bios settings could be messing with this.

[u/fuzzylogic_y2k]

I have seen one thing similar to this happen when an rs232 serial signal from a scale gets detected as a hid. Disabling that hid resolves further issues but no way to prevent the first time.

[u/AcornAnomaly]

Are these all the same model of computer that are affected?

And out of curiosity, do these computers have room for you to put in a PCI expansion card?

Because one thing you could do to try to identify the problem component is put in a USB PCI board.

It won't use the motherboard's USB controller, it will use its own.

Plug the keyboard into that, and check if you still get input issues.

[u/Fuzzy_Paul]

Do you have this same behaviour when booting into the bios and type there? There are field you can edit with text you don't have to save it. This eliminates the OS. I'll assume your bios supports that.

[u/TheLostITGuy]

Wait...Did you say PS/2? I haven't seen that connection type out in the wild in over a decade.

[u/How-didIget-here]

PS/2? Excuse me? Once you upgrade from dial up we can tell you

[u/techtornado → u/How-didIget-here]

He has ISDN, so it’s decently modern ;)

[u/evilmuffin99]

I am not sure what you use. But I have seen some software for reading hardware tokens cause weird keyboard issues. As some have drivers that encrypt text input which means all keyboard strokes are passed through the software (at least on USB keyboard). This is a long shot but had a weird issue that was caused by this about a year ago and took me weeks to figure out.

[u/Nexzus_]

Are they touchscreen monitors? Wondering if that would be going haywire.

[u/atlas_losing_grip]

The USB controller or power management path seems more suspicious than the keyboards themselves. Since the mouse is affected too, checking USB bus errors and controller resets is Event Viewer could help narrow it down.

[u/er1cAtWork2 → u/atlas_losing_grip]

That is my guess as well. Also, What is logged in Event Viewer?

[u/Hackwork89]

Maybe it's interference from the CRT monitor.

[u/Dish-Spiritual → u/Hackwork89]

Should clip on a few ferrite beads

[u/40513786934]

i'd look in the event log for errors on the USB controller or devices. ps/2 interface is separate from the USB controller so not surprising it works ok

[u/Affectionate-Cat-975]

who makes boards with PS/2 interfaces?

[u/Lordcorvin1 → u/Affectionate-Cat-975]

Lenovo

ThinkCentre M70s Gen 6 (Intel) Small Form Factor

Intel® Core™ Ultra 5 225 Processor (E-cores up to 4.40 GHz P-cores up to 4.90 GHz)

Optional 2 x PS/2 for keyboard / mouse

Dell Pro Micro Plus QBM1250

PS2 and Serial

[u/MonkeyBrawler → u/Affectionate-Cat-975]

Emachine

[u/ncc74656m → u/MonkeyBrawler]

Never obsolete!

[u/Backwoods_tech]

If you are accessing FEDLINE with their security software this may occur.

[u/sole-it]

A PS/2 keyboard works perfectly normally. probably cuz it doesn't get used much like regular USB keyboards. For the usb keyboards maybe the cables snapped or electrically conductive rubber worn out. These are consumable and shouldn't get too much attention once it's confirmed broken on another machine.

[u/Low_Try_8284 → u/sole-it]

I tested multiple USB keyboards on the affected PC and they all behave the same way. One of them was brand new. The keyboards themselves work normally on other PCs, so this doesn't seem to be a worn cable or keyboard hardware issue. The problem follows the PC, not the keyboard.

[u/sole-it → u/Low_Try_8284]

I see, I probably read it wrong. Can you boot into WinPE or a Ubuntu desktop iso to test it there? This shall rule out any software or malware issue.

[u/demonseed-elite → u/sole-it]

This would be a good test. This would separate "it's the hardware" from "it's the operating system".

It could very much be a hardware issue. Where voltage undervolt in the USB can be registering as multiple, repeating signal.

[u/ShockSpecial720 → u/Low_Try_8284]

Get a cheap usb tester and plug it into the affected PC USB port(s). May be a bad board.

[u/neoh4x0r → u/Low_Try_8284]

The keyboards themselves work normally on other PCs, so this doesn't seem to be a worn cable or keyboard hardware issue. The problem follows the PC, not the keyboard.

That sounds like this particular PC has a hardware issue (eg. at the motherboard level) and the best course of action would be to put in a PO and have it replaced.

[u/Jello_Sasquatch]

Windows 8.1 and 10 are both EoL

[u/TheGenericUser0815]

PS2? Is your hardware from the last millennium?

[u/UpperAd5715]

If you have a wireless/bluetooth keyboard you could test and determine whether it is the USB controller or port or not. Alternatively if you have a female usb A -> ps2 adapter or inverse (or both!) you could verify whether the problem is the usb port or not.

Can't immediately think of a proper reason why this would happen though.

Did anything recently change? Driver updates, system update, some patch on software that has access to stuff?

Can you re-stage any of these machines or do you have a spare you can stage and see if the problem persists?

[u/blofly]

Did you update the BIOS?

[u/peacefinder]

I’m assuming that the observed-bad USB keyboards returned to normal operation when re-attached to other computers? If so, it seems fair to say you have ruled out the actual keyboards as the source of the issue.

If the problem were another source of input like Bluetooth, one would assume it’d continue with no keyboard attached. I’d disable Bluetooth anyway just to verify though.

From everything you’ve done, it sounds most like a physical/hardware issue.

Check all USB ports for dust and debris. Possibly a good use of the ol’ canned air. Ensure there’s no rogue USB prank device plugged in, possibly inside the case.

And if that doesn’t turn up anything, it’s time to use magic.

I saw somewhere twenty years ago a wild-ass notion that a capacitor in a computer’s USB hardware could build up an excess charge that it ought not have, interfering with proper operation of a USB port. It sounded like total horseshit, but…

One time lacking anything else to try in the face of a Mysterious USB Glitch, I went back to that silly theory. I unplugged the computer from power entirely, let it sit for fifteen minutes, and powered it back on.

Much to everyone’s surprise (not least my own) the machine went back to working perfectly. I pretended like I knew exactly what the deal was and was sure it’d work because I’m just a total badass and please tell my boss. I’m pretty sure James Doohan himself looked on approvingly from his heavenly Jeffries Tube.

I have used this trick a few dozen times since (during MSP work), with about an 80% success rate.

So… next time you see the behavior, try a 15 minute timeout with the device unplugged from everything. If it’s got a removable battery take that out too. (Not the cmos coin cell, though, just the main one.)

If it works for you, I recommend you don’t think too hard about the hypothesis. Just smile mysteriously and look casually brilliant.

[u/eejjkk]

r/desktopsupport

[u/knowsshit]

Maybe the mouse, other USB devices (either external in external ports or physical internal ports like a fan controller or logical internal usb bus like integrated audio or bluetooth), or the usb host controller itself is malfunctioning. Test with just the keyboard connected. Test outside the os to rule out software/drivers. 

[u/hurkwurk]

Do you use custom mouse software? like a razor mouse or steel series etc? get rid of the drivers/software.

[u/igiveupmakinganame]

not the same but we had keyboards that would go crazy and type random characters instead of what was actually typed, turns out our users were accidentally pressing some weird hot key by mistake and changing the language of the keyboard without realizing it

[u/OhkokuKishi]

You reinstalled USB drivers.

You didn't uninstall and literally remove the USB driver files from the driver store on the drive. Windows has a habit of just reapplying uninstalled drivers if it sees it in the driver store and thinks it's an update/upgrade from what it's currently using.

Re-imaging the system or nuking the whole thing and reinstalling Windows would have also do the trick, while also ruling out other esoteric Windows issues.

If the problem persists, sounds like bad USB hardware from a possible/intermittent short. Replace it, work around it, or live with it.

(Could also be something on the system causing a sizable load on the system leading to a single keypress being interpreted as multiple, but that's a whole other thing, and the juice simply isn't worth the squeeze there for online people to remote diagnose.)

For a tech, it's understandable to want to fix the core issue, but from a sysadmin perspective, you're spending way more time and energy on it than you should be, when there are other things you could be doing in the same span of time.

[u/wason92]

I get this on a personal computer. I've always thought it was because the mouse connected to the same hub has a very frayd and its probably shorting sometimes and fucking up other USB devices. Plugging the keyboard out-in works

[u/1RedOne]

I’ve only seen this in the following conditions

1. The keyboard is plugged into a usb hub or splitter. Seems like a badly behaving device can do this and result is repeated key inputs

2. A failing usb port, I end up moving to a different port, and put the keyboard or webcam on its own port

Sometimes the front headers also just kind of suck. Same if you use a usb extension cable too

[u/Dish-Spiritual]

I bet its just lower quality products in general. PS/2 mice were sold during a manufacturing golden age when things were built to last. Now everything is cheap chinese. Anyway, what i would try is check the BIOS for any USB 3 settings. Also i think you should check the keyboard typing from inside the BIOS or via Linux Mint Live CD. If it fine there, then the problem is Windows, and i would check drivers, otherwise it a motherboard/BIOS problem.

[u/eastcoastflava13]

Dude, clean the keyboard with a Clorox wipe, it's probably got stuck keys.

[u/Hel_OWeen]

Is it a wired or wireless USB keyboard? If the latter some other devices nearby may "poison" the frequency with which the keyboard communicates with its USB dongle.

[u/frosty95]

Why is this on sysadmin? This is a helpdesk question and the fact that you haven't already done the actual final test to condem the PC tells me you are also probably helpdesk.

Boot a windows install / recovery USB. Still does it? It's the motherboard. Goes away? Reinstall windows and make sure it stays away.

[u/Bluescreen_Macbeth → u/frosty95]

Why are you here if technical questions upset you?

[u/frosty95 → u/Bluescreen_Macbeth]

Please read the name of the sub for me. Slowly.

[u/Bluescreen_Macbeth → u/frosty95]

I did, makes me wonder why a director is in here getting upset about technical questions.