301 keyboard error

Ah, the 301 keyboard error. The POST error you might be able to fix with your bare hands, or could require a soldering iron. Hopefully that doesn’t scare you off. It’s more frequently a pretty easy fix, especially if the PC isn’t terribly old.

What the 301 keyboard error means

301 keyboard error
A 301 keyboard error usually indicates a stuck key or a bad cable connection. But sometimes, especially on an older machine, it can indicate a problem on the motherboard.

The 301 number simply refers to the order standard PCs conduct their self test in. The codes start at 100 and can range into the thousands. In early PCs, they tended to end somewhere in the 2000s. But they gave a technician a good idea where to start when faced with a dead PC in the field. Codes in the 100 series refer to the motherboard itself. The 200 series codes cover the system memory and related subsystems, and the 300 series refers to the keyboard or controller.

301 technically means the keyboard didn’t respond correctly. But it’s really a pretty generic error. Probably the most common reason I’ve seen it is a key being stuck, something sitting on the keyboard, or the keyboard not being plugged in correctly. One time I had to fix traces on an old motherboard to clear a 301 though. But usually it’s pretty simple.

Troubleshooting a 301 keyboard error

To troubleshoot a 301 keyboard error, make sure nothing is sitting on the keyboard and none of the keys are stuck. One time I spent a good 15 minutes trying all kinds of crazy things before I realized one of the control keys on the keyboard was wedged down. I pried out whatever had it stuck with a paper clip, and the error cleared.

With the most obvious thing out of the way, check to make sure the keyboard is firmly and correctly plugged in. Keep in mind some keyboards have a connection at the computer and at the keyboard, so check both plugs. If either is loose or disconnected, plug them back in correctly.

The overwhelming majority of the time I see a 301 error, it’s related to the above. And this goes back decades. I can’t recall if I helped anyone with this error when I was selling computers at retail, but I sure did when I started as a desktop support tech in the fall of 1995. I “fixed” a lot of keyboards.

If that doesn’t clear the error, it’s time to suspect the keyboard. Try the keyboard on another computer and try a different keyboard on that computer. If the keyboard doesn’t work on another computer, you have a bad keyboard. That’s somewhat rare, but I’ve seen it happen. Unless the keyboard is rare or valuable, replace it.

If a second keyboard gives you trouble, but works on another computer, you have a keyboard controller or connector problem.

The keyboard connector

Check the keyboard connector itself first, before getting too far. Sometimes the keyboard connector gets fouled with chemicals, and you may be able to see it from the outside. If you see anything other than the usual black plastic and metal contacts inside, the connector has sustained chemical damage. Sometimes you can clean it up with vinegar, followed by isopropyl alcohol. If it’s too far gone, you may have to desolder the keyboard connector and replace it with a new one. Practice on a junk board before you try this on a motherboard you care about.

Fixing the keyboard controller

301 keyboard error
This motherboard had damaged traces near the keyboard connector. This caused keyboard problems, but it also kept the computer from working at all. I had to clean up the damage and patch the bad traces, but I was able to bring it back to life.

One time in college, my buddy down the hall had this problem, and nothing he tried worked. I opened the computer up, and he had a chip popped up out of his socket. Presumably that was his keyboard controller. I pushed it back down into the socket and his computer worked fine after that. That’s the only time that’s ever happened to me, but sometimes the fix is easy. If your motherboard has any socketed chips, press down on all of them to make sure they’re seated.

Battery damage

On older computers it’s usually not that easy. Computer batteries tend to be near the keyboard connector. The keyboard connector has traces running to a chip, usually some variant or derivative of an Intel 8042. Both tend to be very close to the battery on many vintage computer designs. If the battery leaks, it spews strong chemicals onto the board, which can eat away the traces, given enough time. Given that many vintage computers have now spent over 20 years sitting unused in storage, they’ve had ample time to do their damage. You’ll need to clean it away with vinegar, then patch the trace.

If you have older computers around, be sure to open them up sooner rather than later and check for leaky batteries. Snip out any old barrel-type batteries you find. Then, even if you don’t work on the machine for a while, it will be ready for you without major board damage to clean up.

The keyboard controller chip or socket

In some cases the controller chip itself could be damaged or bad. If it’s in a socket, you can pop the chip out and replace it. If the socket itself is damaged, that’s a tougher repair, involving desoldering the socket, repairing any traces or vias, replacing the socket, then replacing the chip. Get some help from someone who has done this before if you’ve never done this type of repair yourself.

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