Zealio swap - Failed diodes troubleshooting help (Solved)

[HesterDW]

Hi everyone. Yesterday I swapped my MX Blues with Zealios and everything seemed to work fine until I put it in my case. My only explanation is that something inside my case shorted something out. Upon close inspection you can see exposed copper near some of the joints.This is my first keyboard "build" and so I need advice on the next course of action in the troubleshooting path.

So far I've replaced the switches with others, so I know they're not faulty switches. Then I tried to repair the missing enamel with clear nail polish. I checked the controller and all connections look fine.

Now I'm thinking either it's the diodes or I burned something out completely. I'm not really sure where to go next from here.

[suicidal_orange]

Have the pads the switches are soldered to lifted off?  Looks like some have (left of D146 and D147) others I can't really tell...

If so that's your problem, and instead of hiding the exposed copper you'll need to expose some more on the areas around the raised circles and solder to them.  From the size of those areas it's like the designer knew this would happen - very helpful of them!

[HesterDW]

Have the pads the switches are soldered to lifted off?  Looks like some have (left of D146 and D147) others I can't really tell...

If so that's your problem, and instead of hiding the exposed copper you'll need to expose some more on the areas around the raised circles and solder to them.  From the size of those areas it's like the designer knew this would happen - very helpful of them!

The pads look fine. I tried the wire trick, and the left solder points for each dead switch register a press. But if I try that on the right solder points, connected to diodes, I get nothing.

That must mean it's the diodes right?

[suicidal_orange]

What is this wire trick you speak of?  If you touch one pin to the other on the same switch with some wire it should register the keypress, but if you're touching something else to only the left or right leg nothing should happen on either.  Connecting the left leg of one switch to right of another will probably register something too, but no necessarily either of the keys involved...

You said this is a switch swap so that means the board was working before you started?  I doubt you've managed to kill any diodes, your work looks too clean for that

[Tactile]

I don't know if this is part of the problem but I don't like the look of the solder at D94 at the top of the photo.

[HesterDW]

What is this wire trick you speak of?  If you touch one pin to the other on the same switch with some wire it should register the keypress, but if you're touching something else to only the left or right leg nothing should happen on either.  Connecting the left leg of one switch to right of another will probably register something too, but no necessarily either of the keys involved...

You said this is a switch swap so that means the board was working before you started?  I doubt you've managed to kill any diodes, your work looks too clean for that :)

The wire trick is what you described. I don't know why I called it a trick lol. Using the wire I connected the left leg of a dead switch to the right leg of a working switch. This registered the working switch, which tells me a signal can flow through the left leg of a dead switch. But if I use the wire to connect the left leg of a working switch to the right leg of a dead switch nothing registers.

It seems no signals are going to the right legs of dead switches. On this board each right leg has a corresponding diode. This is what lead me to believe that the diodes are dead.

I tried exposing more copper but that didn't work. So it doesn't seem to be the pads, controller, or switches. You say my soldering looks too clean for diodes to be dead, which leaves me both flattered and perplexed as to what to do next. :p

I don't know if this is part of the problem but I don't like the look of the solder at D94 at the top of the photo.

That diode fell off and was re-soldered by yours truly. The solder refused to stick to the pads even with extra flux. It would just ball up. It's ugly, but it does flow and that switch works fine.

[HesterDW]

I don't know if this is part of the problem but I don't like the look of the solder at D94 at the top of the photo.

I think you were actually onto something. Playing around with this wire I've kinda learned a bit more about how this keyboard's circuit works (and maybe all keyboards?)

The trace for D94 (F1 diode) also runs to D119 (1), D122 (Q), D122(A), D147(Z), and D175(Winkey). All these keys also happen to be dead.

So it seems like something is wrong at D94, I just don't know how to go about fixing that. The only thing that confuses me is that the F1 key actually works. I would expect if something is wrong at D94 then F1 wouldn't register.

[suicidal_orange]

You are on to something and that is how all keyboards work.  When we amateurs make a board we usually connect all the switches along a row and the other legs down the (approximately, due to stagger) columns making it easy to see, reference and fix, but commercial designs don't for whatever reason.

Despite this all switch matrixes work by having "rows" and "columns" and which switch has been pressed is found by where these intersect, so a break in these traces can take out one or many switches.  I should have asked which ones were not working as this would have made it obvious that the problem is along the trace you have coloured in!

If the switch at the top attached to D94 is F1 and works, and all the others below along your red line are not working then when the diode was broken off it seems that it broke the trace heading right, but not left.  If you solder a wire from the black end of D94 to the black end of D119 to bypass that damaged trace the rest of the switches should return to life.

If not please post a pic of a bigger section of the PCB including the controller chip, or if that's on a separate board where the connector that goes to it is is good enough

Good spot Tactile!

[HesterDW]

If the switch at the top attached to D94 is F1 and works, and all the others below along your red line are not working then when the diode was broken off it seems that it broke the trace heading right, but not left.  If you solder a wire from the black end of D94 to the black end of D119 to bypass that damaged trace the rest of the switches should return to life.

Ohhhh, that makes so much sense now. F1 was connected to the controller but everything after that wasn't. I ended up repositioning the diode and bridging it to the trace with some wire. Everything works now. 



This has been quite the learning experience. Thanks for the help you guys! 

[asdfjkl36]

YAAAY HAPPY ENDING!!!!

Good detective work guys


Now we need to fix Sed's NerD.

[Tactile]

 

[suicidal_orange]

Interesting fix but it works so all good. and you've learned something

NerD you say asdfjkl36?  Hopefully that's not the one with the dodgy LEDs...

Also can you rename the thread by editing the OP?  The title suggests there's a problem with Zealios, but there isn't

[HesterDW]

Interesting fix but it works so all good. and you've learned something

NerD you say asdfjkl36?  Hopefully that's not the one with the dodgy LEDs...

Also can you rename the thread by editing the OP?  The title suggests there's a problem with Zealios, but there isn't

Good point...title changed.

[asdfjkl36]

Interesting fix but it works so all good. and you've learned something

NerD you say asdfjkl36?  Hopefully that's not the one with the dodgy LEDs...

Also can you rename the thread by editing the OP?  The title suggests there's a problem with Zealios, but there isn't

That's the one.

https://geekhack.org/index.php?topic=76920.0

[suicidal_orange]

Good point...title changed.

Thanks

That's the one.

https://geekhack.org/index.php?topic=76920.0

I've not learned LEDs yet - they're next on my list!

Thankfully it looks to be solved, awaiting a new transistor...