Author Topic: [Help] QWERTY Row Not Working on Keyboard After Desoldering  (Read 1755 times)

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Offline Blurify

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[Help] QWERTY Row Not Working on Keyboard After Desoldering
« on: Sat, 19 June 2021, 17:07:56 »
Hi, I wanted to change the switches on a Durgod K320, but discovered that the entire QWERTY row (from Tab to PgDn) does not register while I was testing the desoldered PCB. This was my first time desoldering, and I know that I have lifted multiple pads. I'm hoping that there is still some way for me to fix this row, otherwise the keyboard would have very limited use.

Additionally, some other keys did not work, but I believe that I have fixed them with switch bridges. Also, the entire FN row also does not work and I believe that it is due to some lifted pads as well as a detached copper trace on the other side of the PCB. This row is not as important as the one in question, but I would like to fix this row as well if it is possible.   

Pictures: https://imgur.com/a/ZR0OGLz

Offline suicidal_orange

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Re: [Help] QWERTY Row Not Working on Keyboard After Desoldering
« Reply #1 on: Sat, 19 June 2021, 17:23:06 »
Definitely a lot of lifted pads, and two of them being the important ones where the rows link to the controller chip.  Sadly it's a black PCB so it's very hard to see what's going on, but the controller chip is above the arrows so and there are no traces running vertical on the front of the board so they must be on the back.  Can you make out a trace heading down from the lower/right pin of a switch on the back, or can you take a pic where the light highlights the traces in that area?

As long as all the damage is at the switch end of the traces it's quite easy to fix, assuming the traces aren't close to others the whole way.
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Offline Blurify

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Re: [Help] QWERTY Row Not Working on Keyboard After Desoldering
« Reply #2 on: Sat, 19 June 2021, 18:31:16 »
Thanks for the quick response, here's some pictures of the traces: https://imgur.com/a/p5roS6F

Offline suicidal_orange

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Re: [Help] QWERTY Row Not Working on Keyboard After Desoldering
« Reply #3 on: Sun, 20 June 2021, 07:03:41 »
That's the right kind of picture but they don't show the switches above the arrows where the damaged traces start or the controller chip where they end.  Please try again :)
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Offline Blurify

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Re: [Help] QWERTY Row Not Working on Keyboard After Desoldering
« Reply #4 on: Sun, 20 June 2021, 14:16:41 »
Sorry about that, I just updated the pictures in the link

Offline suicidal_orange

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Re: [Help] QWERTY Row Not Working on Keyboard After Desoldering
« Reply #5 on: Sun, 20 June 2021, 16:31:20 »
Did I mention how much I hate black PCBs?  I really do >:D  I still can't see anything helpful beyond saying it doesn't look like the QWERTY row connects from the DEL END or PGDN switches where it would make sense to put the connections.  But it's a commercial PCB so that's not really surprising.

Lets try another angle - can you read the text on the controller chip and post it?  Maybe a datasheet will show which pins the switches could be connected to, then you can do some poke testing to find out which has been disconnected.
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Offline Blurify

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Re: [Help] QWERTY Row Not Working on Keyboard After Desoldering
« Reply #6 on: Sun, 20 June 2021, 21:04:11 »
The text on the controller chip is: ARM STM32F070. Here's a picture of the chip: https://imgur.com/a/w0WtHYo

Offline Blurify

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Re: [Help] QWERTY Row Not Working on Keyboard After Desoldering
« Reply #7 on: Tue, 22 June 2021, 21:01:27 »
I'm not sure if this is useful, but I was trying to find ways to activate a keypress on the QWERTY row and was not able to do so no matter what I tried. I found that whenever I bridge a working switch with one of the switches on the QWERTY row, the remaining switches on this row to the right of the bridged switch would activate keypresses for another row.

Offline suicidal_orange

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Re: [Help] QWERTY Row Not Working on Keyboard After Desoldering
« Reply #8 on: Tue, 22 June 2021, 23:25:52 »
Sadly that doesn't help, it's standard.  Each 'column' is set live then depending which row returns the signal it knows which key connects the two.  It's the trace from the dead row back to the chip that's broken, your bridge connects the two rows so it gets confused.  If you can see a trace heading other than straight across the lower pins of the dead row that's the one.  Not easy on a black PCB.

Life is very much in the way, I'll have a look for the chip in ... 11 hours when I get home and hopefully it's standard and they didn't invent their own model number to write on it.
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Offline Blurify

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Re: [Help] QWERTY Row Not Working on Keyboard After Desoldering
« Reply #9 on: Tue, 22 June 2021, 23:31:44 »
No worries, I appreciate your help. In the meantime, I'll look for the trace you mentioned.

Offline suicidal_orange

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Re: [Help] QWERTY Row Not Working on Keyboard After Desoldering
« Reply #10 on: Wed, 23 June 2021, 12:43:54 »
Two dots and one cut corner - helpful.  I found the pinout on page 24 here but without knowing which corner pin 1 is in that's not much help.  Hopefully you can find the trace!
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Offline Blurify

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Re: [Help] QWERTY Row Not Working on Keyboard After Desoldering
« Reply #11 on: Thu, 24 June 2021, 02:52:14 »
Would this trace be on the front or the back of the PCB? The trace heading that is straight across the lower switch pins that you mention appears to be on the front side of the PCB. I was able to find a few other traces which I have drawn out in the images here: https://imgur.com/a/xN6slp1

I want to note that the colors of the drawn traces in the images are not significant, and are only used to differentiate what I think are separate traces.

Offline suicidal_orange

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Re: [Help] QWERTY Row Not Working on Keyboard After Desoldering
« Reply #12 on: Thu, 24 June 2021, 03:15:10 »
The traces finish on the back and as they would have to cross a row or 3 to get to the chip at least part of the vertical bit must be on the back but there could be multiple vias (the holes which link the two sides) along the way.  pic looks helpful but not on a phone screen so I'll look properly later.
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Offline yui

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Re: [Help] QWERTY Row Not Working on Keyboard After Desoldering
« Reply #13 on: Thu, 24 June 2021, 04:21:29 »
do the enter key work? giving fast look at your traces it looks like it may with a bit of luck be on the same row as qwerty, so maybe connecting the bottom pin of the enter key to one of the top pin of one of the dead key could revive it? (sorry only saw this post and only looked at the last photos)
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Offline Blurify

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Re: [Help] QWERTY Row Not Working on Keyboard After Desoldering
« Reply #14 on: Thu, 24 June 2021, 11:05:53 »
There are two areas for Enter key switches, which I assume is to support a layout with a big Enter keycap, and both work. However, when I connect the bottom pin of either of these two Enter keys to the top pin of a switch in the QWERTY row, the keys on the QWERTY row register keypresses that correspond to the ASDF/Enter row.

Offline suicidal_orange

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Re: [Help] QWERTY Row Not Working on Keyboard After Desoldering
« Reply #15 on: Thu, 24 June 2021, 11:11:39 »
Still no go, there must be a trace going down attached somewhere along the red line going across the middle.  Given that it's damaged I would expect it to be attached to one of the switch pins (which are also vias) - does the red trace above \| attach to the switch pin?  It's going the wrong way but at least it's going vertical.  If it stops at a via maybe you can find it on the other side.
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Offline Blurify

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Re: [Help] QWERTY Row Not Working on Keyboard After Desoldering
« Reply #16 on: Thu, 24 June 2021, 12:42:10 »
I think I have found the problem. I looked at the vertical trace above the \| switch pin and found that it connects the bottom pin of this switch to a via on the front side of the PCB which leads to an exposed trace at the Insert and Home keys of the number row. I have included pictures where I have drawn the traces at the \| switch pins (colored yellow) and the two vias (colored orange and pink) they are connected to, as well as a close up of the exposed trace here: https://imgur.com/a/xN6slp1

Offline Blurify

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Re: [Help] QWERTY Row Not Working on Keyboard After Desoldering
« Reply #17 on: Thu, 24 June 2021, 12:47:10 »
There is also a similar exposed trace in the FN row which I assume is likely the reason why the this row also does not work.

Offline suicidal_orange

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Re: [Help] QWERTY Row Not Working on Keyboard After Desoldering
« Reply #18 on: Thu, 24 June 2021, 12:59:50 »
I have no idea what via 1 is doing, that pin should be connecting to a diode.  Could be the bonus one next to Del...

Via 2 puts Ins, Home and PgUp in the QWERTY row though which could be useful - do any of them work?

Assuming there is some kind of logic to this board (there may not be) that would mean that Del, End and PgDn should be connected to the ASDF row - left right pin of ' to right left pin of Del should type Del?  If so you can solder right pin to right pin to bring them back.
« Last Edit: Thu, 24 June 2021, 13:03:14 by suicidal_orange »
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Offline Blurify

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Re: [Help] QWERTY Row Not Working on Keyboard After Desoldering
« Reply #19 on: Thu, 24 June 2021, 22:52:03 »
Only the PgUp key works. Unfortunately, the pad of the left pin of Del is lifted, but when I connect the right pin of Del to the left pin of ', it registers '. When you say solder the right pin to the right pin, which switches are you referring to? When I bridge the right pins of ' and Del, all of the keys in the ASDF row register, but they were already doing so previously. I tried to bridge the right pins of Insert and \|, but this does not result in the QWERTY row registering any keypress. I then tried to bridge the right pins of PgUp and \|, but that results in the switches on the QWERTY row registering keypresses on the number row. Currently, the PgUp, End, and PgDn register. The other three keys (Insert, Home, and Del) do not.

Offline yui

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Re: [Help] QWERTY Row Not Working on Keyboard After Desoldering
« Reply #20 on: Fri, 25 June 2021, 02:31:16 »
one thing i did not see in the tread, are you using ansi or iso layout? (vertical or horizontal enter key?)
 - if you are on iso have you tested the ansi \| key above the ansi enter key? should be on the qwerty row, to me it would me little sense to cross above the controller with a row trace but then my experience with keyboard matrices is limited.
 - if you are on ansi please disregard this message.
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Offline Blurify

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Re: [Help] QWERTY Row Not Working on Keyboard After Desoldering
« Reply #21 on: Fri, 25 June 2021, 03:46:18 »
I am using ANSI layout.

Offline suicidal_orange

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Re: [Help] QWERTY Row Not Working on Keyboard After Desoldering
« Reply #22 on: Fri, 25 June 2021, 11:11:05 »
my experience with keyboard matrices is limited.
Just assume anything non DIY was designed by someone on lots of drugs - neither of the Enter key positions nor the ANSI \| even have a diode nearby on this one, there can be no other reason for that!

Only the PgUp key works.
...
Currently, the PgUp, End, and PgDn register. The other three keys (Insert, Home, and Del) do not.
Um...

When you say left or right are you looking at the front or the back of the board?  It's unusual to have access to the front so I'm used to talking from the back, that may not be helping!

Delete doesn't work because the left pad is broken, looks like it connects to the bottom of the lower diode next to it (once confirmed solder a bridge to the diode).  I've put everything else together on one of your early pics - your board is wired like this where all the same coloured dots are connected:
271265-0

If the red 'circle' is around a broken trace sticking up that's the break that's taking out the whole QWERTY row and you have no choice but to solder to that trace.  You could cut it off and scrape off the black mask a little further along, or you could solder to the loose bit and then glue it down (hot glue works best)  You will also need a bridge between the greens on Insert and Home to reconnect that row.

On the Fx row it looks like Pause/Break should still be working so all you need to do is bridge the two cyan pins.
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Offline Blurify

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Re: [Help] QWERTY Row Not Working on Keyboard After Desoldering
« Reply #23 on: Fri, 25 June 2021, 19:38:26 »
When I say left and right, I am referring to the back of the board, I'll specify which side of the board in the future.

Just to be sure, I am: 
1. Soldering a bridge between the two pins (left and right) of the Delete key if they are connected
2. Soldering either the loose end of the broken trace (or the exposed copper after cutting the loose trace) to the area marked by the red circle in the image

How would I confirm that the two pins of Delete are connected, when the left pad (relative to the back of the PCB) is broken? Also, would I have to scrape off the black mask at the area marked by the red circle to expose the copper before soldering to it?

Offline suicidal_orange

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Re: [Help] QWERTY Row Not Working on Keyboard After Desoldering
« Reply #24 on: Sat, 26 June 2021, 02:31:13 »
If you solder left to right of Delete that's the same as holding the switch down - not advisable

There are two diodes next to delete, one of them should have a trace going to the left (back) switch pin next to it - that's where to solder the bridge.  This can be confirmed by shorting a blue dot to the diode which will type Delete.  If you short to the wrong end of the diode it will still type Delete but you don't want to solder there or you'll get ghosting, so look first.

The broken trace circled in red should be connected to the green dots.  The floating bit has no black on the back or sides so no need to scrape it, but it is fragile.  Usually cutting it off and scraping a bit attached to the board is better but there's another trace right below which you really don't want to scrape (a short there would link QWERTY and 12345)  Maybe you can find the trace on the back to find a better place to scrape but the via is right next to the via on the trace below so they probably run parallel all the way to the chip and I don't think it will get any easier.  I guess you could hold a ruler over the lower trace to protect it while scraping, that should work...  I know what needs doing but I've never actually done a scrape repair so sorry for being a bit fuzzy.
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Offline Blurify

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Re: [Help] QWERTY Row Not Working on Keyboard After Desoldering
« Reply #25 on: Sun, 27 June 2021, 05:22:19 »
Quote
If you solder left to right of Delete that's the same as holding the switch down - not advisable

Haha, I see that now.

Here are some pictures that I refer to in the text below: https://imgur.com/a/DjP1P8l

Quote
There are two diodes next to delete, one of them should have a trace going to the left (back) switch pin next to it - that's where to solder the bridge.  This can be confirmed by shorting a blue dot to the diode which will type Delete.  If you short to the wrong end of the diode it will still type Delete but you don't want to solder there or you'll get ghosting, so look first.

I think I have found the correct end of the diode to solder a bridge to the left (back of PCB) switch pin of the Delete key. Would I be soldering the wire directly onto the end of the diode as I have shown in the picture?

Quote
On the Fx row it looks like Pause/Break should still be working so all you need to do is bridge the two cyan pins.

The two cyan pins are lifted, would I still be able to solder a bridge between them?

Quote
The broken trace circled in red should be connected to the green dots.

Would I do this as shown in the picture I have provided? I have decided to cut off the loose end of the trace since it was already very loose. In the picture, I would solder the loose end of the trace to the green dot corresponding to the left (front of PCB) switch pin of Home and then solder another wire from this pin to the end of the trace marked by the red circle in your picture.


From my understanding, I should be making bridges with wires and fixing the loose trace with solder correct? Also, would I have to solder my switches before creating the bridges? The loose trace on the front of the PCB would be blocked by the switches, so the order that I plan on taking is to:
1. Fix the loose trace on the front of the PCB
2. Solder the switches onto the PCB
3. Create the desired bridges

Sorry for asking so many questions, I'm new to soldering and I do not want to damage the keyboard anymore than I already have.


Offline Blurify

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Re: [Help] QWERTY Row Not Working on Keyboard After Desoldering
« Reply #26 on: Fri, 02 July 2021, 13:00:34 »
Bump. I've purchased flux and more leaded solder, looking forward to the approval or any corrections you have for me before I start.

Offline suicidal_orange

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Re: [Help] QWERTY Row Not Working on Keyboard After Desoldering
« Reply #27 on: Fri, 02 July 2021, 13:52:25 »
Ah sorry, missed this.

Unless you have copper foil you can't fix the trace on the front (your wire going through the switch hole will stop the switch pushing all the way in) so you'll have to find it on the back, the pink dot is the via which should be easy to spot as there are two together.

You will want to solder in the switches (as much as possible) before doing any bridges, the pads are mostly gone so you'll be soldering to the switch pins instead.  Getting some solder in the holes to help hold the switches in is still good, flux will help.

Delete is as you say - solder the diode end first then the switch pin.

If both cyan in your pic are lifted then pause doesn't work?  I think the via is the yellow dot between the two cyan pads so you'll need to see where that goes on the back and scrape that too.

So your bridges would be the blue lines (some of which don't go anywhere as they only make sense on the other side of the board!)

271672-0
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Offline Blurify

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Re: [Help] QWERTY Row Not Working on Keyboard After Desoldering
« Reply #28 on: Sat, 03 July 2021, 03:19:55 »
No worries, I was too busy to work on it during the week anyways. From my understanding, I should be soldering on the back like so:

271688-0

When you say that I have to scrape, do you mean that I have to scrape away the black bits from the trace of the vias (pink and yellow) and solder directly to it? Also, when you say that I have to solder to the switch pins, are you referring to the pins on the switch itself when they are soldered onto the PCB? (Sorry if this is obvious). Just to be clear, when I solder these bridges (whether it be to a diode, switch pin, or scraped via trace) I am using wire rather than solder correct?
« Last Edit: Sat, 03 July 2021, 03:23:34 by Blurify »

Offline suicidal_orange

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Re: [Help] QWERTY Row Not Working on Keyboard After Desoldering
« Reply #29 on: Sat, 03 July 2021, 04:36:42 »
A little background on soldering and electronics in general :)

The only thing that matters is what's connected to what.  Usually you would solder the switch pin to the plated hole in the PCB and they become one entity known as a solder joint which you can solder a bridge to.  When you pull up a pad the plating through the hole usually comes out too so there is no way to solder the pin in that hole and no pad to solder to - the only way to connect the switch is to solder directly to the pin.

When it comes to scraping the black off you could scrape the via or anywhere down the yellow and pink traces (I'm assuming you checked those vias are connected to the switches as I still can't see thanks to the blackness) - the controller has no idea whether you soldered to the switch hole, the leg on the chip itself or anywhere in between, all it knows is the signal came in on that pin.  If the trace is ever in space that's a good place to scrape so you don't expose the trace next door but be careful and scrape along the trace slowly with something sharp and it should be ok.

And yes you solder the end of wires, any wire will do as it wont be thinner than a trace.

Good luck :)
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Offline Blurify

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Re: [Help] QWERTY Row Not Working on Keyboard After Desoldering
« Reply #30 on: Sat, 03 July 2021, 15:26:46 »
Quote
I'm assuming you checked those vias are connected to the switches as I still can't see thanks to the blackness

I'm not sure how to verify this, should the vias be connected to the microcontroller for this to be true? Here is the best picture I can give of the relevant traces as well as the drawn traces for the vias in question:

271707-0
271709-1

Offline suicidal_orange

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Re: [Help] QWERTY Row Not Working on Keyboard After Desoldering
« Reply #31 on: Sat, 03 July 2021, 16:40:09 »
It's the front I was worried about - that those vias are connected to the switches.  Wherever the switches were connected is where they need to be reconnected, looking at the latest pics it looks very likely.

If you're feeling brave and the pink one is right it might be just as easy to solder the bridge to the leg on the chip as it's on the corner, depends how confident you are at soldering.
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Re: [Help] QWERTY Row Not Working on Keyboard After Desoldering
« Reply #32 on: Sun, 04 July 2021, 05:12:50 »
Before I start soldering, there was one more issue that I forgot to mention. I think the damaged trace on the bottom row near the Space key has caused the Space, left Ctrl, left Windows, and left Alt keys to stop working. When I say left keys here, I am referring to the front of the keyboard. However, I was able to activate a keypress for each of these keys by touching a wire from the right pin (back of PCB) of the right Alt key to the left pin (back of PCB) of these keys. However, when I create this bridge for each key, touching both of the pins of that key still does not result in a keypress. Every key to the right of the Space key works, its just the Space key and all of the keys to the left of the spacebar that do not. The Space key probably does not work due to the lifted pad as well.

This is what the drawn trace on the front of the PCB looks like:
271745-0

This is the back:
271747-1

In the second picture, the yellow lines are the traces and the other colored lines are the bridges that result in each key being pressed


Offline suicidal_orange

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Re: [Help] QWERTY Row Not Working on Keyboard After Desoldering
« Reply #33 on: Sun, 04 July 2021, 10:56:07 »
That long yellow trace is wrong, it's probably a short one to the diode and another one going further up from the LED pads.  There's no relevant vertical trace there anyway as the chip is on the other side, and the single trace running along the bottom is where the damage is.

If those bridges work and the damage is on space you should just be able to solder one bridge between the lower pads of both Alts (and maybe an extra one to space) then the switches will all work.
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Re: [Help] QWERTY Row Not Working on Keyboard After Desoldering
« Reply #34 on: Sun, 04 July 2021, 11:58:24 »
Quote
solder one bridge between the lower pads of both Alts
This works, making the left Alt, left Windows, and left Ctrl keys work

Quote
(and maybe an extra one to space)
Would this bridge would be between the lower pad of right Alt and directly to the lower switch pin of Space since its lower pad is lifted?

Offline Blurify

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Re: [Help] QWERTY Row Not Working on Keyboard After Desoldering
« Reply #35 on: Sun, 04 July 2021, 12:28:35 »
I'm also just finding out that the += key does not work on the Num row and I suspect it is due to its upper pad (back of PCB) being lifted. I find that when I bridge the upper pad (back of PCB) to ]} to that of +=, the key works. I think what is happening is that the upper pin of += is no longer connected to its diode and the bridge connects it to another diode. Would it be correct to do this, and/or would it make a difference if I were to solder the pin of += to its corresponding diode? Its a bit unclear to me which diode is the one corresponding to this switch based on the traces, and if this makes no difference I will use it.

Offline suicidal_orange

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Re: [Help] QWERTY Row Not Working on Keyboard After Desoldering
« Reply #36 on: Sun, 04 July 2021, 14:04:33 »
No, you can't just use another key's diode, it will result in multiple keys activating when you press one.  Looks like there are two diodes between = and - and there's a trace from the top pad of = on the front going to a via which probably comes out under the diode, so as on the other switches you can just bridge the top switch pin to the diode.

And yes, lower pin/pad of either Alt to lower of space will reconnect it to the row.
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Re: [Help] QWERTY Row Not Working on Keyboard After Desoldering
« Reply #37 on: Tue, 06 July 2021, 00:32:21 »
Quote
If you're feeling brave and the pink one is right it might be just as easy to solder the bridge to the leg on the chip as it's on the corner, depends how confident you are at soldering.
The ends of the wire are much larger in comparison to the legs of the chip. I will likely make the bridge to the corner leg, since I do not have to worry about the wire being connected to any legs below it. However, the other bridge will actually go to the leg that is two legs above the corner leg, which is significantly more difficult since I have to make sure that the bridged wire does not connect to the any legs above or below it. I just want to make sure that I still have the option of scraping and soldering the bridge to that exposed area instead. I remember you mentioning that I cannot solder to the front traces since they consist of copper foil, but is this the case for the back? 
« Last Edit: Tue, 06 July 2021, 00:34:15 by Blurify »

Offline suicidal_orange

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Re: [Help] QWERTY Row Not Working on Keyboard After Desoldering
« Reply #38 on: Tue, 06 July 2021, 03:18:48 »
You can solder to the traces on the front but you can't solder the switch on the front as the wire will raise the switch, meaning it doesn't clip into the plate and feels and looks wrong. Whether you want to scrape both traces on the back or solder to the corner pin is entirely up to you, the signal will still get to the pins eventually.  If the wire is thick you probably want to scrape, though as the pins are tiny most wire will be bigger.
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Offline yui

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Re: [Help] QWERTY Row Not Working on Keyboard After Desoldering
« Reply #39 on: Tue, 06 July 2021, 06:27:18 »
one thing i did use once to solder to an SMD component was a copper strand from electrical multi-strand flexible wiring, pain to extract, to use and you need to make sure it does not touch anything else (not insulated at all) now i have some magnet wire to do the same job that is in a roll and has some insulation, you can also get some of that very thin magnet wire from 12V fans and low current motors, if you have one dead lying around. still going to be a pain to solder, but maybe a bit less so
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Offline Blurify

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Re: [Help] QWERTY Row Not Working on Keyboard After Desoldering
« Reply #40 on: Fri, 09 July 2021, 05:31:29 »
Update: I have now soldered all of the switches and bridges. All of the keys work and I am currently typing on the keyboard. Thank you suicidal_orange and yui for helping me during the last three weeks to fix my keyboard, I really appreciate it.

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Offline suicidal_orange

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Re: [Help] QWERTY Row Not Working on Keyboard After Desoldering
« Reply #41 on: Fri, 09 July 2021, 08:02:36 »
Soldering to the tiny controller pin in the middle is a feat that was refused by a professional PCB repair place someone sent their board to - good work!

Enjoy your new switches :)
120/100g linear Zealio R1  
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'Split everything' perfection  
MX Clear
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Offline Blurify

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Re: [Help] QWERTY Row Not Working on Keyboard After Desoldering
« Reply #42 on: Fri, 09 July 2021, 11:06:15 »
Thanks, I tried to solder to the trace, but I couldn't get the wire to connect to the scraped trace. I'm not sure if the trace area was too small, but I tried to bridge the wire to the trace several times without any success. I would tin the wire and trace with solder and then apply flux to the trace before bridging, but I was not able to create a bond between the wire and trace. I'm still surprised that the wire only connects to the third leg of the chip, it took me a few tries to get that correct as well.