Author Topic: Broken PCB Trace Help!  (Read 672 times)

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Offline Nytalix

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Broken PCB Trace Help!
« on: Wed, 16 September 2020, 03:42:17 »
Hi, I'm new to the website but kinda oldish to the hobby? I just got serious about the hobby earlier this year.

So, I have a broken PCB trace from an 65% Ajazz board I was modding. I accidentally pulled out a good chunk of the PCB trace from the right arrow key to the down arrow key. I've tried fixing this problem by placing copper tape over the ripped traces and from where the trace was left. This instead activates the entire bottom row from control to the left arrow key. I think I ripped out the only trace that bridges the other rows to the bottom row. I've tried looking for a bridge to restore the connection to the down and left arrow keys, and the entire bottom row I guess. I tried bridging the down arrow key to the right arrow key and the up arrow key with no luck, I also tried it on the right arrow key with the same effect.

I don't know much about PCBs and all that stuff, but I did read 2 forum posts here with similar problems, the solution to the first forum post was scraping off some excess solder from an LED light, while the other one's original post was changed so I can't exactly see what was the original problem. So I finally made a geekhack account to see if anyone can help me.
« Last Edit: Wed, 16 September 2020, 03:44:50 by Nytalix »

Offline yui

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Re: Broken PCB Trace Help!
« Reply #1 on: Wed, 16 September 2020, 04:07:39 »
on your last image your copper tape is shorting switch 70, so this is one problem, and you may want to clean your flux residues as some of them can be conductive and short one of your now exposed copper trace to the led. at 1st glance it is all i see that could be very wrong, but i dunno the specifics of this pcb so multimeter in low resistance mode may be your best friend with this, the lower the resistance the closer you are to your short
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Offline Nytalix

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Re: Broken PCB Trace Help!
« Reply #2 on: Wed, 16 September 2020, 04:49:29 »
I've been hearing about the multimeter for a while but I don't actually know what it does and how it works. Other than that, a friend of mine told me to solder in a small enough copper wire to replace the broken trace.

Also, here's a better look at the pcb trace. The keyboard is an Ajazz K680T
« Last Edit: Wed, 16 September 2020, 05:58:34 by Nytalix »

Offline yui

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Re: Broken PCB Trace Help!
« Reply #3 on: Wed, 16 September 2020, 07:09:30 »
well soldering would work but with that missing pad it will be a bit harder, when you try to plug in the keyboard without your copper tape fix the entire row activating? and the problem with seeing anything on your photos is that the pcb is black making the traces really hard to see. or impossible on the edges.
For the multimeter take a cheap one, and do not plug it into the mains to test it, if you keep it on the V position on powered board (voltmeter mode) and Ω on unpowered boards (ohmmeter/resistance meter mode) you should be safe as long as there is no mains on the board, and to go more in details there are millions of videos explaining it, EEVblog and ElectroBOOM are good sources.
and yes you are right that the down and right arrow keys should be linked, but not the up arrow, and you will need to find an other place that same row goes to (that still register) and solder your wire there cause it seems that the left arrow is part of the same row but may be connected to the controller through the broken part.
and to test if an emplacement still registers just need to take tweezers or a piece of wire and short the contacts while the board is plugged into a pc. as long as you are not using a mac you should be ok even if you short the usb (try not to do it though)
vi vi vi - the roman number of the beast (Plan9 fortune)

Offline Nytalix

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Re: Broken PCB Trace Help!
« Reply #4 on: Wed, 16 September 2020, 12:37:47 »
yes, it does activate the entire row, when I cover the missing trace with copper tape.

Offline suicidal_orange

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Re: Broken PCB Trace Help!
« Reply #5 on: Thu, 17 September 2020, 00:11:07 »
Damn black PCBs, can't see anything!

Am I right seeing the broken trace going up then across above LED 69 where the white line has been pulled up, then the trace snapped above LED 70?  If so you could scratch off some mask there and solder to the trace, or just keep following it until it gets to the controller with it's helpfully exposed pins.  A picture of that corner of the board would be good if there's any way to highlight the traces in the shine.

You need to be careful the copper doesn't touch the other pin on the switch, looks like it is which is probably why the whole row activates.
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Offline Nytalix

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Re: Broken PCB Trace Help!
« Reply #6 on: Thu, 17 September 2020, 01:15:33 »
And you are right, that is the pcb trace. I did try scratching off the mask and placed copper tape over it connecting it to the pcb holes missing the trace i.e 69 and 70 It just did the same thing as before but Im not sure if I did it properly though.

I tried following the trace and it lead me to these 2 highlighted holes I think. I also followed the trace from the back and it just lead to the other side of the pcb with no real connector
« Last Edit: Thu, 17 September 2020, 01:17:45 by Nytalix »

Offline yui

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Re: Broken PCB Trace Help!
« Reply #7 on: Thu, 17 September 2020, 02:09:32 »
if your trace following is good and if the up arrow still registers i would try to connect the down arrow to the up arrow and see if both register as they should, if it does then you traced correctly and can just fix it by soldering wires between that up arrow(58) contact and the down(69) and left arrow(70). if it does not then the black solder mask fooled you :)
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Offline Nytalix

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Re: Broken PCB Trace Help!
« Reply #8 on: Thu, 24 September 2020, 23:42:29 »
Hi, sorry for the late update but I just got my multimeter

69 and 70 are producing voltages less than 6 while most of the sockets produce voltages more than 15

Offline yui

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Re: Broken PCB Trace Help!
« Reply #9 on: Fri, 25 September 2020, 01:04:03 »
what are you measuring? USB should not go over 5.5V (5V + theoretical cable loss) so i do not think you are in volt mode there, or there is something very strange with your pc. i would try to put it into ohm mode and scratch a bit of solder resists off the broken trace (red rectangle), put one lead on exposed copper on that trace and try to find a pad that has a low resistance to it (a few ohms) with the other lead, it would be on the same side of a switch or on the controller. if you need help i will try to follow
« Last Edit: Fri, 25 September 2020, 01:15:02 by yui »
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Offline Nytalix

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Re: Broken PCB Trace Help!
« Reply #10 on: Fri, 25 September 2020, 12:33:29 »
what are you measuring? USB should not go over 5.5V (5V + theoretical cable loss) so i do not think you are in volt mode there, or there is something very strange with your pc. i would try to put it into ohm mode and scratch a bit of solder resists off the broken trace (red rectangle), put one lead on exposed copper on that trace and try to find a pad that has a low resistance to it (a few ohms) with the other lead, it would be on the same side of a switch or on the controller. if you need help i will try to follow
Thanks for the heads up, yeah my multimeter was set at volts, I have it at 200m Ohms now. I did what you asked, scratched some of the black coat off of the pcb then put copper tape over it. I checked out some pads to see how much Ohms I'd get, it was around 1.3 - 1.4 but for socket 70, 199.8 would flash on my multimeter then it'd go to 1.

I also tried putting the positive wire on the copper tape and the negative in nearby sockets, It'd reach aound 65-85 Ohms, does that mean anything?

Offline yui

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Re: Broken PCB Trace Help!
« Reply #11 on: Sat, 26 September 2020, 12:01:58 »
Thanks for the heads up, yeah my multimeter was set at volts, I have it at 200m Ohms now. I did what you asked, scratched some of the black coat off of the pcb then put copper tape over it. I checked out some pads to see how much Ohms I'd get, it was around 1.3 - 1.4 but for socket 70, 199.8 would flash on my multimeter then it'd go to 1.

I also tried putting the positive wire on the copper tape and the negative in nearby sockets, It'd reach aound 65-85 Ohms, does that mean anything?
so if you get a 1 on the left side of the screen it means overload, in case of resistances it is not dangerous, it just means it is to high to measure, make sense given that the trace is broken. in ohm mode positive and negative leads do not matter at all as long as you are not across a diode, and i do not think you needed the tape, if your tape did not short to any other trace, i think that if you put a link between your missing pad (70), the same pad on 69 and one of those you got very low resistance to it may work, hopefully. else more testing to do
vi vi vi - the roman number of the beast (Plan9 fortune)

Offline Nytalix

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Re: Broken PCB Trace Help!
« Reply #12 on: Sat, 26 September 2020, 12:17:45 »
Thanks for the heads up, yeah my multimeter was set at volts, I have it at 200m Ohms now. I did what you asked, scratched some of the black coat off of the pcb then put copper tape over it. I checked out some pads to see how much Ohms I'd get, it was around 1.3 - 1.4 but for socket 70, 199.8 would flash on my multimeter then it'd go to 1.

I also tried putting the positive wire on the copper tape and the negative in nearby sockets, It'd reach aound 65-85 Ohms, does that mean anything?
so if you get a 1 on the left side of the screen it means overload, in case of resistances it is not dangerous, it just means it is to high to measure, make sense given that the trace is broken. in ohm mode positive and negative leads do not matter at all as long as you are not across a diode, and i do not think you needed the tape, if your tape did not short to any other trace, i think that if you put a link between your missing pad (70), the same pad on 69 and one of those you got very low resistance to it may work, hopefully. else more testing to do
I see so do I just put some copper tape on the missing pad on 69 then try to connect it with the pcb trace via copper wire?