Member Avatar for ulcimd1

When this computer booted, there was no keyboard functionality. I disconnected the keyboard, then plugged it into a different USB port. The lights came on, so I opened IE,a and selected the search box (Google) and the box began filling with plus signs.(++++++++++....) I disconnected the USB extension cable and cold booted the computer. Without the extra cable, the computer seemed nearly normal...(when i tested the KB, it added a couple of random plus signs into the characters.) The plus sign on the NUM pad was not physically stuck down, but it didn't work either. All the other keys produced output except that one. Could this really be as simple as a stuck key under the button...(I know that an eleven year old boy uses this computer frequently, and though I see no obvious spills, who knows?!) Instead of stuck button, maybe I should say malfunctioning button. I really want to resolve this because I have experienced this once before, and I discounted it as aresult of the computer being very, very old. As I previously mentioned, there was an extension cable to the usb port, and there is a rat's nest of wires (not literally) behind this computer. Is it an RFI or EMI issue, or just keyboard issue?
----After thinking this through a few minutes, and testing the extension cable on a separate device, I feel that the problem is purely in the keyboard.

  • 2 Contributors
  • 3 Replies
  • 232 Views
  • 1 Day Discussion Span
  • Latest Post Latest Post by mechbas

Dani AI

Generated

As discovered, a keyboard that suddenly "streams" a single character is almost always a hardware problem — usually a stuck/shorted switch, conductive residue bridging the key matrix, or a failing controller inside the keyboard. RFI/EMI is an unlikely culprit when the behavior follows the keyboard between ports or machines; was right to point at contamination as a common cause.

Quick troubleshooting checklist:

  • Unplug the keyboard and test it on a different computer (no hubs or extension cables).
  • Plug the keyboard directly into a rear USB port on the PC to rule out a flaky hub/port.
  • Reproduce the problem outside the OS (enter BIOS/UEFI or use a live/rescue boot); if the plus signs appear there, it is hardware.
  • Verify which physical key is producing the plus: numeric keypad plus vs. shift+'=' — they are different switches.
  • Use a simple key-tester utility or the OS on-screen keyboard to watch for phantom key events.
  • If a replacement keyboard immediately fixes it, replacement is the practical solution.

Basic cleaning/repair steps (if you want to try to salvage the keyboard):

  • Unplug first. Remove the suspect keycap carefully (key puller or small flat tool).
  • Blow out debris with compressed air and inspect for sticky residue.
  • Use a cotton swab lightly moistened with 70–90% isopropyl alcohol to clean around the switch; do not soak the PCB. For mechanical switches, contact cleaner helps; for membrane keyboards, disassembly and careful rinsing of plastic parts may be needed.
  • Let everything dry completely (24+ hours) before reconnecting.

Final notes: cheap replacement keyboards are often cheaper and more reliable than repair. To avoid repeats, keep liquids away, use a cover, and avoid long USB extension cables or cheap hubs that can hide the real source of trouble.

Member Avatar for mechbas

The inside of the kbd is obviously contamimated, as you noted, spilled drinks that act like glue to any dirt, lint, etc.
>>>RFI or EMI issue, or just keyboard issue
do you have another server to try it on?

Member Avatar for ulcimd1

Well, a twenty dollar keyboard from Wal-Mart solved the problem. It just struck me as very strange that only the one key was affected, just like the last time I had this problem. Thanks for your help though. What a heel I am!

Member Avatar for mechbas

O.K., live and learn. Life without it would be fairly dull, yes?

Be a part of the DaniWeb community

We're a friendly, industry-focused community of developers, IT pros, digital marketers, and technology enthusiasts meeting, networking, learning, and sharing knowledge.