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[Solved] CTK-3000. One key deactivates touch sensitivity in some others

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Hello,

 

I have a CTK-3000 keyboard which has an issue with the touch sensitivity.

When I keep pressed the 3rd G#, it makes the following 7 keys, until D# sound super loud. If G# is not pressed, all those keys sound normally.

If a do it in the reverse way, I press first any of these keys and then I press the G#, it also works normally. But if then I add a 3rd key, this one sounds loud again. So G# is the one that produces the other give loud sound.

 

It happens both with touch sensitiviy level 1 & 2. If I remove the sensitivity, everything works.

 

It really seems to be a defect on the PCB (electronic board). If disassembled almost the hole keyboard, but it is difficult to discover the possible failure if I don't know exactly what am I looking for.

 

I've seen this issue in another keyboard, but the suggested solutions (replace the keyboard) is not available for me.

Although my keybord is brand new, it has been stored in a warehouse for years, so it is out of warranty.

 

Is there any way to fix it by myself?

 

Thanks,

 

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While  your problem could be a bad circuit chip or a defective ribbon cable connector, problems like this are often caused by dirty or corroded key switch contacts.  You will find a set of dimpled rubber contact strips under the keys.  Try lifting these off and cleaning the pc board contacts and the insides of the dimples with rubbing alcohol and cotton swabs.  Do not use any other solvent, or anything that contains water, and be very gentle with your cleaning action.

 

Good luck !

 

Regards,

 

Ted

 

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Hello Ted. Thanks for your advice. I've disassembled the hole keyboard and I've removed some dust, but unfortunatelly, the problem persists. I've discarted a rubber strips issue, as I've switched its position and the problem keeps at the same key.

 

After that, I've been checking the board around the affected zone and I've discovered a welding mistake (attached picture), which can be the origin of the problem.

 

Tomorrow I'll repair this welding. I'll let you know if it has worked or not.

 

Thanks!

20170304_110609.jpg

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Glad you got it sorted and that you now have a working keyboard, but that means that the problem had to exist since you bought the keyboard.  There is no way that solder would have flowed from one connection to the other at room temperature, and if that circuit chip had ever got hot enough to melt the solder, it would have been fried.  I'm surprised you did not notice the problem back then, but all's well that ends well.

 

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Yes, of course it was a manufacturing defect. But I bought this keybord last week. It had been stored for years in a shop and I got it at good price (I think!), as it was brand new.

I noticed the problem in the first day I had it.

But as you said, all's well that ends well.

:)

 

Thanks!

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Wow, glad I saw this-I've done alot of repairs including many soldering projects. Word to the wise-sloppy soldering isn't your friend, and apparently can come out of the factory like this! One tiny solder bridge created all this havoc, and fortunately didn't short this hard to replace SMT chip. Never assume everything has been put together properly! I have repaired several keyboards simply by opening them, and refitting a loose cable or connector. It happens.

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Yeah, Johnathon, I was studying those pics yesterday.  I think we are looking at the bottom (non-component) side of the board.  From the looks of those 6 or 7 or 8 leads coming through from the top side, it appears that the top side components were floatation soldered, but those 3 or 4 diodes here on the bottom side could not have been done that way.  I am betting that they were manually (human) mounted and soldered (oops !) after the floatation process.  So much for quality control testing !

 

 

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