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From: rabbit killer on 26 Jul 2010 23:23
why the hell does my flashlight go dim, but when I knock it hard it gets
bright again? What can I do to fix this? I don't understand what's going
on here...
From: Tom Biasi on 26 Jul 2010 17:03

"rabbit killer" <siccusproprius(a)gmx.com> wrote in message
news:i2kqt6$b95$1(a)news.albasani.net...
> why the hell does my flashlight go dim, but when I knock it hard it gets
> bright again? What can I do to fix this? I don't understand what's going
> on here...

The bulb is getting less voltage than it needs.
Most likely cause is contact resistance.
Clean every place contact is made.
Battery ends, spring to battery, bulb to battery, switch contacts. A pencil
eraser works on most of it. If the switch is sealed you don't need to worry
about it.
Also check where the reflector rim touches the contact and make sure the
bulb is tight.
Did I miss anything guys?

Tom


From: pimpom on 27 Jul 2010 03:30
Tom Biasi wrote:
> "rabbit killer" <siccusproprius(a)gmx.com> wrote in message
> news:i2kqt6$b95$1(a)news.albasani.net...
>> why the hell does my flashlight go dim, but when I knock it
>> hard it
>> gets bright again? What can I do to fix this? I don't
>> understand
>> what's going on here...
>
> The bulb is getting less voltage than it needs.
> Most likely cause is contact resistance.
> Clean every place contact is made.
> Battery ends, spring to battery, bulb to battery, switch
> contacts. A
> pencil eraser works on most of it. If the switch is sealed you
> don't
> need to worry about it.
> Also check where the reflector rim touches the contact and make
> sure
> the bulb is tight.
> Did I miss anything guys?
>
Only the possibility that the OP was trolling.


From: Michael Black on 27 Jul 2010 10:41
On Tue, 27 Jul 2010, pimpom wrote:

> Tom Biasi wrote:
>> "rabbit killer" <siccusproprius(a)gmx.com> wrote in message
>> news:i2kqt6$b95$1(a)news.albasani.net...
>>> why the hell does my flashlight go dim, but when I knock it
>>> hard it
>>> gets bright again? What can I do to fix this? I don't
>>> understand
>>> what's going on here...
>>
>> The bulb is getting less voltage than it needs.
>> Most likely cause is contact resistance.
>> Clean every place contact is made.
>> Battery ends, spring to battery, bulb to battery, switch
>> contacts. A
>> pencil eraser works on most of it. If the switch is sealed you
>> don't
>> need to worry about it.
>> Also check where the reflector rim touches the contact and make
>> sure
>> the bulb is tight.
>> Did I miss anything guys?
>>
> Only the possibility that the OP was trolling.
>
Huh?

The original problem is pretty common, and I sure remember knocking
flashlights about in order to get them working again.

Flashlights are simple, and have virtually no soldered parts. So the
contact between the bulb and the rest of the circuit is merely pressure
contact, the switches are often on a similar level.

Those can suffer, maybe the worse because of the current drain of the
bulb.

LED flashlights don't suffer because they aren't put together with
pressure, and there's no surge as the bulb first receives current and
heats up.

Michael

From: ehsjr on 27 Jul 2010 10:56
Michael Black wrote:
> On Tue, 27 Jul 2010, pimpom wrote:
>
>> Tom Biasi wrote:
>>
>>> "rabbit killer" <siccusproprius(a)gmx.com> wrote in message
>>> news:i2kqt6$b95$1(a)news.albasani.net...
>>>
>>>> why the hell does my flashlight go dim, but when I knock it
>>>> hard it
>>>> gets bright again? What can I do to fix this? I don't
>>>> understand
>>>> what's going on here...
>>>
>>>
>>> The bulb is getting less voltage than it needs.
>>> Most likely cause is contact resistance.
>>> Clean every place contact is made.
>>> Battery ends, spring to battery, bulb to battery, switch
>>> contacts. A
>>> pencil eraser works on most of it. If the switch is sealed you
>>> don't
>>> need to worry about it.
>>> Also check where the reflector rim touches the contact and make
>>> sure
>>> the bulb is tight.
>>> Did I miss anything guys?
>>>
>> Only the possibility that the OP was trolling.
>>
> Huh?
>
> The original problem is pretty common, and I sure remember knocking
> flashlights about in order to get them working again.
>
> Flashlights are simple, and have virtually no soldered parts. So the
> contact between the bulb and the rest of the circuit is merely pressure
> contact, the switches are often on a similar level.
>
> Those can suffer, maybe the worse because of the current drain of the bulb.
>
> LED flashlights don't suffer because they aren't put together with
> pressure, and there's no surge as the bulb first receives current and
> heats up.
>
> Michael
>

Spot on, except for the thing about LED flashlights.
You're probably sensible enough to buy *good* ones.

The cheap ones I've seen sure do, but not because of high
current. Some of them use a solder ball (blob?) to
contact the battery + terminal, and a crappy spring at
the other end. Dissassembly, cleaning, sometimes stretching
the spring, and sometimes adding to the solder ball restores
operation. For a while. :-)

Ed
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