FW3A FW3C FW3T tailcap button mod - o-ring helps but click doesn't always trigger

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fogus
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Cleaned it with 99.9% and replaced the o-ring with the 008 size. Light is happy and so am I.

A big THANK YOU to all!

fogus
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And the problem is back. Unless I press dead-center with just the right pressure, it won’t toggle.

I just want to order a replacement PCB at this point to try that. Can anyone help me find out where to buy one?

JaredM
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Do you have a soldering iron?

fogus
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Yes, and I’m OK with it. Not a master, but I’ve done several hundred small connections.

fogus
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What should I do with the soldering iron?

jon_slider
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fogus wrote:
What should I do with the soldering iron?

I think the aswer might be in post #9 and #18

I hope you figure something out

Firelight2
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fogus wrote:
What should I do with the soldering iron?

These switches are very simple. They consist of a flat plastic pcb, a flexible springy metal “popper” and a strip of Kapton tape holding it all together. When the button is depressed it pushes down the popper which inverts (giving the click sound), while creating an electrical connnection between its corners and center.

The connection might be failing to trigger due to the flexible metal “popper” not properly connecting at the center and edges when the button is depressed. This could be because when the popper clicks and inverts it isn’t quite touching at the center.

The following might be worth attempting:

  • The popper is held on top of the pcb with Kapton tape. Peel off the popper and completely remove it from the pcb.
  • Put a tiny dab of solder paste in the center of the pcb where the popper touches when the switch is depressed.
  • Apply soldering iron to it. The goal is to add a tiny bumb directly where the popper hits. This should cause the switch to reach connection without having to depress quite as much. I would aim small. A dab the thickness of a piece of paper might be all that is needed.
  • stick the popper back in place, reassemble and test.
  • If the switch action is too soft or fails to click, it is quite possible the dab you just added is too tall. Remove the popper and file it down with a small handfile, or use a solder removal tool and reapply the solder.
  • I expect this may take multiple attempts of fine-tuning to get it just right. You might need fresh kapton tape to hold the popper in position if you try this too many times as the glue on the stock tape might wear out.

Some additional notes:

  • I recommend avoiding tampering with the popper unless you’ve given up all hope of anything else working. If you damage or destroy the popper, it might not be reparable. For these reasons I suggest against trying the following except as a last resort:
  • If the problem is connection between the corners of the popper and the pcb, one possible solution is to solder one corner in place while leaving the others floating. The downside is any heat applied to the popper might destroy its springiness and destroy the switch. A better option is probably to completely remove the popper and clean all corners with deoxit.
  • Another option that might improve springiness is to bend one or all of the corners slightly down. In theory this might mean more tension is required to actuate the switch. But again, the risk of permanently destroying the popper is high.

JaredM
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Sorry for leaving that hanging. Fireflight nailed it. Exactly as I was going to recommend. Cleaning the popper and pcb again with alcohol AND deoxit d100 or gold would be first for me. Cleaning the first time seemed to help, maybe some flux was missed on the bottom side of the popper. Simplest things first.

Otherwise, the super short solder bubble/dome on the center pad is what I believe should cure this.

We’ll be here for any other questions. Good luck!

Oli
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Put the nubin back in and very gently press the switch in various directions 50+ times and see if you can duplicate the failure.

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