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geekhack Community => Keyboards => Topic started by: darkclone24 on Tue, 13 March 2018, 14:23:01

Title: PCB RGB LEDs - Most Not Working, Advice Needed
Post by: darkclone24 on Tue, 13 March 2018, 14:23:01

Hi guys, been a while since I was around here.

Been using my ZZ96 for a while at work, and noticed that only 2 of the underside RGB LEDs are working. This is easiest to see in the pictures here:

https://imgur.com/a/wENOl (https://imgur.com/a/wENOl)

I was hoping just to see a lose connection that I could solder up, but I suspect there's a component failure. Can anyone advise if there is an easy way to diagnose the issue?

Thanks

Title: Re: PCB RGB LEDs - Most Not Working, Advice Needed
Post by: crystalhand on Tue, 13 March 2018, 15:19:31

I dont see anything on the board that looks like it may be responsible.  There is some weirdness in the bottom right of the board but i think it may be a picture artifact.

I would grab the trusty volt meter and  see if the leds are getting any power.  Trace back until you find where that trace has power. This will tell you where the broken component/trace is

Title: Re: PCB RGB LEDs - Most Not Working, Advice Needed
Post by: redbanshee on Tue, 13 March 2018, 15:27:59

The same thing happened to my zz96. I had an exploded RGB led (https://i.imgur.com/HkRbZ94.jpg (zoom in)), i replaced it with a new one. These pcb's were from a not-that-great fab house and they all came with a bunch of re-works done by someone trying to fix them after getting them semi working from the fab house in china.

Title: Re: PCB RGB LEDs - Most Not Working, Advice Needed
Post by: donut_sauce on Tue, 13 March 2018, 15:48:44

Quote from: crystalhand on Tue, 13 March 2018, 15:19:31

I would grab the trusty volt meter and  see if the leds are getting any power.  Trace back until you find where that trace has power. This will tell you where the broken component/trace is

This is what I would do. Then if it is the led just replace it.

Title: Re: PCB RGB LEDs - Most Not Working, Advice Needed
Post by: darkclone24 on Tue, 13 March 2018, 16:52:16

None of my LEDs look like that, redbanshee. Looks like I'm gonna have to pick up a volt meter (or even a multi meter) tomorrow for testing.

Thanks for the responses.

Title: Re: PCB RGB LEDs - Most Not Working, Advice Needed
Post by: darkclone24 on Thu, 15 March 2018, 14:37:12

Seems that there is voltage to all of the LEDs (Red pin on Anode and Black pin rotating between Cathodes), to the tune of 5.00 when set to 20V.

A few of the under-cap LEDs aren't on, however when testing I found that the pins were causing the LEDs to light up. I could resolder to get these working, but I somehow doubt that would help the SMD LEDs.

I can't view the traces on the front of the board without desoldering every single switch; is there any possibility that I'd be able to see the issue on the other side of the PCB?