Subject: Re: [Shop-talk] led flashlight troubleshooting

From: Battmain <[email-masked]>
Date: Tue, 24 Dec 2013 14:27:47 -0800 (PST)

I have one, also from China. On mine, which uses three batteries, it has to do
with the cheap metal. Sometimes it is the contacts at the bottom of the LED
assembly or the base that the assembly contacts, sometimes, it is at the
spring end.  At the spring end, the stopper/insulator, whatever you want to
call it, moves, and that either causes a short or no contact at that end.
Taking it apart and reassembling will work until the next time is moves from
the spring pressure. 

Regards,
Brian

>________________________________
>
From: John Niolon <[email-masked]>
>To: shop-talk <[email-masked]>
>Sent: Tuesday, December 24, 2013 5:11 PM
>Subject: [Shop-talk] led flashlight
troubleshooting
> 
>
>recently bought 4 of these little led flashlights and
was well pleased...
>
>http://www.amazon.com/BBQbuy-300lm-Flas ... flashlight
>
>I found them again from another vendor (both in china) and ordered more to
>give to friends at Christmas... well the last 4 came and not a one of them
>worked... vendor gave a refund and I started tinkering... I have juice to the
>led assembly in the business end of the light...but no light... anyone know
of
>a way to test led assemblies... it's only about 1/2" in diameter and
totally
>sealed (it seems) any suggestions ???
>
>thanks
>john
>
>(snip)
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Archive: http://www.team.net/archive

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From: "Arvid Jedlicka" <[email-masked]>
Date: Wed, 25 Dec 2013 08:40:09 -0600

I do not have that specific flashlight but have experienced intermittent and 
DOA with other small imported flashlights.

In all of my cases it was related to the way the PCB that the LED mounts to 
returns current to the battery. The PCB is a circular affair which has a pad 
in the center of it that presses against the center battery\battery holder 
post. This provides one side of the circuit. The outer diameter of the 
circular PCB also has pads on one side of it. Think single sided PCB, not 
two sided or with plating on the edges of the PCB, but only on one normal 
flat side of the PCB. These pads on the flat part are suppose to contact a 
"ledge" in the the metal body of the flashlight. This ledge provides the 
return circuit and also prevents the PCB from falling into the body of the 
flashlight.

The current flow is "battery -> pad in the center of the PCB -> LED and 
related current regulating circuits -> pads on the flat outer diameter of 
the PCB -> ledge on flashlight body -> flashlight body -> switch in the cap 
on the end of the flashlight body -> spring in the switch\cap -> other end 
of the battery.

In all cases my failures were related to the PCB being a very poor press fit 
into the flashlight body and the outer diameter pads not contacting the 
ledge. If I would press on the lens to push the PCB into the body they would 
light up. Note that "press ..." did not actually cause the lens to move any 
discernable amount. All is seemed to do was press the outer diameter 
contacts down hard enough to actually press against the ledge and work.

The pressing incantation seemed to permanently fix some of them but for 
others it was 'only worked while pressed'. Needless to say those that would 
only work if I had my finger on the top of the lens were classified as "did 
not seem to fit the spirit of useful flashlight design" and were trashed.

Yours may have much better construction techniques.

Arvid

[email-masked]

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From: Jimmie Mayfield <[email-masked]>
Date: Wed, 25 Dec 2013 13:29:57 -0500

On Tue, Dec 24, 2013 at 04:11:00PM -0600, John Niolon wrote:
> recently bought 4 of these little led flashlights and was well pleased...
> 

For some reason my email client munched on the URL so I couldn't look
at the lights in question but the first thing to check (after polarity, etc)
is that the various pieces that screw together are making good electrical 
contact since most flashlight designs use the body as one of the conductors.  

Unscrew everything, and rub the ends back and forth a few times on some 320 
grit sandpaper then use some steel wool to lightly scuff up the threads.
That'll give you good electrical contact when everything is screwed back
together.

Another thing to check is that the leads to the LED weren't severed when the
reflector was installed at the factory.  This happened with a couple 
flashlights I bought off ebay.  It's a simple fix if you have a soldering iron
and some ~18-20ga wire.

-- 
Jimmie Mayfield  
http://www.sackheads.org/jimmie         email: [email-masked]
My mail provider does not welcome UCE -- http://www.sackheads.org/uce
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From: Dave C <[email-masked]>
Date: Wed, 25 Dec 2013 11:03:30 -0800

I guess I have been lucky so far; I purchased seven of these a couple of 
months ago over two different orders; no real problems yet.  The first 
batch had a very tight lens focusing ring; on the second batch the ring 
was  loose.  Otherwise they work fine.  I put some silicone grease on 
the threads and put one in each vehicle. Great little lights for three 
or four bucks, if they work.

> http://www.amazon.com/BBQbuy-300lm-Flas  ... flashlight

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