Author Topic: Strange keyboard behavior after soldering in new switches  (Read 432 times)

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Offline esylvester

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Strange keyboard behavior after soldering in new switches
« on: Mon, 23 March 2020, 20:19:42 »

Hello,

I'm looking for some insight into what went wrong or generally what is wrong with this board.

My best theory is that I messed something up while soldering in new switches. I tested EACH key after I desoldered the whole board using the same tester, and everything worked just fine. So nothing got messed up in the desolder process. I can't physically see anything on the backside of the PCB that could be causing this issue. Each solder point appears just fine, and the board doesn't show any signs of damage to any SMD. I have desoldered and soldered many boards in the past. Not to say that makes me invincible to breaking a board, but I do have experience in this case. This is actually the second Masterkeys Pro S that I have desoldered and soldered in new switches. Regarding software, I have tried everything I can find online. I have done all the "reset" and "erase" functions. Nothing changes the behavior of the board.

Thanks


Offline suicidal_orange

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Re: Strange keyboard behavior after soldering in new switches
« Reply #1 on: Mon, 23 March 2020, 20:33:08 »
The grid pattern shows that you have a short, the Filco matrix has the keys connected in U shaped columns so it's every other key that activates.  The fun with R looks to be it seeing the windows and/or alt keys pressed...

Edit: Just looked again and it's not in a case so shouldn't be a cable crushed under the pin as I first thought.
                               
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Offline esylvester

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Re: Strange keyboard behavior after soldering in new switches
« Reply #2 on: Mon, 23 March 2020, 20:47:03 »
Thank you for your thoughts. I've attached pictures of the PCB. I've closely scanned this board back and forth with my eyes looking for any solder that might be contacting something. I can't find anything.

Offline suicidal_orange

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Re: Strange keyboard behavior after soldering in new switches
« Reply #3 on: Mon, 23 March 2020, 20:52:30 »
What's with the switch next to the USB cable socket?  Looks like both pins are shorted to square pads next to them labelled R and +.  Maybe they're supposed to be but that looks weird to me.
                               
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Offline esylvester

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Re: Strange keyboard behavior after soldering in new switches
« Reply #4 on: Mon, 23 March 2020, 21:07:45 »
Yeah that struck me as a problem as well. I figured out that those pads are designated to LEDs. I've desoldered that switch and made sure those pads made no contact. This did not change any of the behaviors.

Offline esylvester

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Re: Strange keyboard behavior after soldering in new switches
« Reply #5 on: Mon, 23 March 2020, 21:32:44 »
FIXED!!! I FIXED IT! I FOUND THE SHORT!

Offline Maledicted

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Re: Strange keyboard behavior after soldering in new switches
« Reply #6 on: Mon, 23 March 2020, 21:38:12 »
FIXED!!! I FIXED IT! I FOUND THE SHORT!

That's awesome to hear. What the heck was behind that tiny blob, in the middle of nowhere, causing a short?

Offline suicidal_orange

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Re: Strange keyboard behavior after soldering in new switches
« Reply #7 on: Tue, 24 March 2020, 05:34:55 »
The stray blob of solder melted through the mask and shorted the traces?  That is unlucky.  Well done for spotting it, any further up and/or right you'd have had no chance :))
                               
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Offline esylvester

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Re: Strange keyboard behavior after soldering in new switches
« Reply #8 on: Tue, 24 March 2020, 15:35:25 »
Update

Okay, now I am just dumbfounded. So the keyboard worked 100% after I removed that blob of solder. I did like 3 successful typing tests and suddenly it relapsed back to its old behavior. I am so confused.

Offline Leslieann

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Re: Strange keyboard behavior after soldering in new switches
« Reply #9 on: Tue, 24 March 2020, 20:45:17 »
Check that you are not pushing pins into the cord.

This is often how it reacts when that happens, works fine then they slowly bite into the cord. It can be extremely hard to spot so look carefully and/or wrap it in electrical tape, that will reveal it better.
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Offline esylvester

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Re: Strange keyboard behavior after soldering in new switches
« Reply #10 on: Tue, 24 March 2020, 21:19:15 »
I don't believe this is the problem. I've held the board up so the cable was making no contact with anything, yet the problems persist.

Offline esylvester

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Re: Strange keyboard behavior after soldering in new switches
« Reply #11 on: Fri, 27 March 2020, 00:47:54 »
Update #2

Okay, I have been obsessed with fixing this keyboard. I desoldered the whole board and cleaned off all of the flux. Today I decided to try something different. I baked the PCB in the oven. I set the temperature to 385 and cooked it for 10 minutes. Lo and behold, it works again ;D!! I let it cool down for a while and tested it using tweezers. Everything appears to be functional! Cheers to the oven method.

Offline pixelpusher

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Re: Strange keyboard behavior after soldering in new switches
« Reply #12 on: Fri, 27 March 2020, 00:56:47 »
What keyboard is in the back at 0:15?

238574-0


Hope it stays fixed!

Wait, is that just a norbatouch?  Ha.  I thought it was like copper color with a white inlay.  I think now it's just the lighting.
« Last Edit: Fri, 27 March 2020, 00:58:31 by pixelpusher »

Offline esylvester

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Re: Strange keyboard behavior after soldering in new switches
« Reply #13 on: Fri, 27 March 2020, 01:20:53 »
What keyboard is in the back at 0:15?

(Attachment Link)


Hope it stays fixed!

Wait, is that just a norbatouch?  Ha.  I thought it was like copper color with a white inlay.  I think now it's just the lighting.

Hah yeah its a Norbatouch! The keyboard inside is Masterkeys Pro S with Box Navies. The keyboard I made this post for is another Masterkeys Pro S. Now I can switch between Box Navies and Box Blacks. One day I'll find another Norbatouch case.

Offline Maledicted

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Re: Strange keyboard behavior after soldering in new switches
« Reply #14 on: Fri, 27 March 2020, 02:26:11 »
Update #2

Okay, I have been obsessed with fixing this keyboard. I desoldered the whole board and cleaned off all of the flux. Today I decided to try something different. I baked the PCB in the oven. I set the temperature to 385 and cooked it for 10 minutes. Lo and behold, it works again ;D!! I let it cool down for a while and tested it using tweezers. Everything appears to be functional! Cheers to the oven method.

Nice, always worth trying if the next alternative is a dumpster. I have baked many a PCB myself. I'm glad this one worked out.

Offline typo

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Re: Strange keyboard behavior after soldering in new switches
« Reply #15 on: Fri, 27 March 2020, 15:34:30 »
When this happens it is an issue of impedance, If you can figure out where the short is, which may be invisible to the naked eye. You can clean it with flux. This is the reason it is so discouraging because often there is nothing you can see. By putting it in the oven you simply "sweated" away any traces inducing the impedance mismatch. Since they are tiny they just boil away and vaporize in seconds. It can even be flux itself.