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C6 switch annoyance.

Marco Polo

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Nov 2, 2012
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I'm having an issue with the switch on my 520nm C6 laser. This has been an issue since I got the host. The laser has been suffering from intermittent failure to power up. All of the solder joints on the LD, driver, and leads are confirmed good. When it fails to power up, if I give the laser a firm shake then it generally powers up at that point. While powered, if I shake the laser around forcefully I can see that the laser is losing power at certain points. Maybe shaking it around isn't good for it, but it shouldn't be losing power at all, even under these circumstances.

On close examination, I'm quite sure that the switch is the problem.

Do you guys generally replace the switch when this happens? I've taken the switch apart and made sure that the metal tabs are making good contact with the host and that the switch body is not loose within the tailcap. It basically works like it's supposed to, except for the intermittent failure to power.

I've done the best I can to ensure that the tabs are making good contact and must at this point conclude that the switch mechanism itself is to blame. At this point, it looks like a replacement switch is in order. I'm fine with this, but I don't know what part number to order.

Can anyone please advise?

Thanks,

MP
 
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will manners

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Narrowing down the cause of the problem is the most obvious thing to do.

You should start by unscrewing the tailcap and checking for continuity whilst the switch is on. If you've narrowed it down solely to the cause of the switch then you can order this and replace it directly onto the switch PCB. Although I'm not 100% sure that the dimensions of this switch match the PCB. You need to double check that.
 

Marco Polo

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Yeah, the conclusion that it was the switch itself was bothering me, these things usually don't behave this way, at least not in my experience.

I took the switch apart again and tested the switch unit for continuity and sure enough I couldn't get it to fail. The whole switch assembly is a "sandwich" consisting of tje retaining ring, which presses a spring against a steel washer, which presses against the switch contact. The whole thing looks like a recipe for crappy electrical contact.

I couldn't get solder to stick to the washer (I didn't expect it to) but I did add some to the big end of the brass spring. I also lightly sanded the washer to remove any surface oxidation or dirt that might have been contributing to the problem. Then I reassembled the switch, taking extra care to ensure that the switch tabs would make firm contact with both tailcap and steel washer.

So far, it hasn't acted up, I guess due to the spring base taking up more room and making things fit tighter. Adding solder to the spring has the added benefit that the spring can no longer be pulled through the retaining ring.

Thanks for the Fasttech link, that looks like it will work. For less than $1.50 it couldn't hurt to get one next time I order from them.

eta: Eh, looks like I'm going to be ordering a new part. Stupid switch just won't work properly. Oh well.
 
Last edited:

Marco Polo

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Well, I replaced the switch on my 520nm and it was still acting up. Damn it, what could be wrong with this thing?

Decided to do a more thorough inquiry at that point so pulled out module/heatsink, removed heatsink, then front tube and checked wires/joints, all ok. Removed pill and noticed it came out too easily. I usually tighten it in with channel locks, so it should have given me a bit of resistance. Also noticed that the battery contact board on this one is recessed compared to the others, so made the positive contact (solder blob) taller just in case. I made extra sure to turn down that pill this time and then reassembled the unit.

So far have not had any further issues with the unit. I really wonder if the pill was too loose and I would expect that to cause intermittent breaks in the circuit. I had the pill out when I worked on it last (fixing a weak solder joint), so maybe I forgot to properly tighten it when I put the laser back together.

The replacement switches from SL are better than the ones the hosts come with anyway, because the spring is soldered in and in general there seem to be less potential for connection issues due to loose parts. Replacing the original switch crossed my mind on those grounds a while ago, but was less of a priority. In any case the lasers are in good shape and I got a good refresher in troubleshooting, so am satisfied all around :)
 




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