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Help with Repeating Keys; Focus FK-555 Keyboard


I have problem with a Focus FK-555 keyboard, which I was hoping someone could help me with.

I use this keyboard on a near native PS2 port (HP laptop docking station), and a Gigaware PS2-USB adapter.  The underlying problem is the same, but the consequences are different depending which method I am connecting to.
It has random keys that repeat, although they most commonly occur on the A, S, and D keys, since they are used the most. I have seen the problem on C, and backspace keys too.

On the near native PS2 port, the problem goes away for the most part if I lower the repeat and delay functions in windows keyboard settings.  However, on the USB-PS2 adapter, problem persists, and mimics stuck keys.  Eventually the keyboard locks up and needs to be unplugged and plugged back in.  It also flickers off the keyboard lights when this happens.

I don't think it is the ALPS switches themselves are the problem in light of the above.  I am inclined to think there is something wrong with the keyboard matrix, data line, keyboard controller.  I suppose there could be something wrong with the keyboard cable itself but I don't have any spares (I was thinking of picking up a soarers internal keyboard converter for that purpose).

Does anyone have any ideas what could be happening, and how I could potentially go about diagnosing this?  I have a digital multimeter. No access to more fancy stuff such as logic analyzer or oscilloscope (not that it would help, have limited proficiency in electronics).  Alternatively, if anyone knows of a shop, or even better yet, one in the Dallas Fort Worth, TX area, that'd be even better.

Have you checked the PCB? Maybe there's some corrosion on some of the contacts, or a capacitor that's gone wrong.

Dr. Ran, your sage keyboard advice eventually led to the solution!  The problem was two part.  First, there was a very small amount of corrosion or detritus (dried out flux or resin ?)  at the contacts of the keyboard connector on the board.  I missed this during my initial inspection of the keyboard.  Putting on a pair of 1.5x magnifying glasses revealed the issue (we're talking about what appeared to be a 3.5 mm particle that bridge the solder points).  Cleaning it off immediately resolved the repeating key issue.  Second, was a bad AT->PS2 connector.  On a whim, I switched out the flexible connector, with a barrel connector.  No more disconnects, whether I used near native PS2, or my PS2->USB adapters from Gigaware and Belkin.

On an unrelated note, I really appreciate your videos!  I had a ****ty keyboard experience at work a few years ago, and thought I was resigned to a life of mediocre keyboards.   Came across your videos (as well as GH and DT), and realized that I didn't have to live with cancer.  Old tech is still good.  Thanks again for taking the time to reply.


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