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Things to check if your flashlight doesn't work.

  • cyclist Moderator Sunday, January 16, 2011 6:55 PM Reply
    Thank you to nakamoomin/Tom for making this post on CPF, if you're reading this and object to it being on DX, please let us know.
    Its only been put here in case the whole forum where you posted this gets deleted, as it has already been changed to members only.

    Also, thanks to UltraMagnus for helping out.

    These so-called budget lights are great value, but both have been “twitchy”. The first (Romisen RC-F4) had an issue with its switch being unreliable. The second (MTE “P7-D”, 5-mode) had a flickering issue. I’m sure others have problems with budget lights, and therefore I’ve made this tiny troubleshooting guide. Feel free to comment as I am a noob with regards to LED flashlights (except for a Luxeon I bikelight I designed and built for an engineering project in university a few years back).

    OK! Here goes!

    img src: http://farm4.static.flickr.com/3604/3397776193_f9e84074e9_o.jpg

    my lights

    These are the lights I will use today (I also have a DX Pig-light, but I’ve never had any issues with it, so recon these are maintenance-free, ha ha), the Romisen RC-F4 and the MTE “P7-D” (5-mode).


    1) Check the batteries!
    If output is dim, but there is no flickering issue, the battery is a likely culprit. Some voltage-regulating circuitry may also flicker when the voltage drops, but this is rare. Remember: If your light uses more than one battery you need to be EXTREMELY careful not to mix-and-match batteries of different capacity or voltage. If you suspect that one of the batteries are dead (sometimes even brand new ones are dead) remove them and get them checked. This goes for all lithium-based batteries, primaries as well as rechargeables. Consider purchasing protected cells as well.

    2) Check the LED

    img src: http://farm4.static.flickr.com/3543/3397852647_da4a2cb8a5_o.jpg

    Visually inspect the LED to see if it shows any sign of being “burnt” (discoloration, dark spots). This should be visible through the lens.

    3) Check the solder-points and contact-points

    img src: http://farm4.static.flickr.com/3593/3397891395_07beeb9ffa_o.jpg

    Visually inspect the solder-points by removing the head. If this is not possible remove the bezel and extract the glass and reflector if possible. Some heads are glued (such as the MTE “P7-D”) but it may still be possible to access the LED/pill by removing the bezel/lens/reflector. Be very carful not to touch the reflector. It is polished and aluminium is soft. If you don't know what you're doing cleaning it is likely to ruin it! Wipe the lens when you reassemble. If everything seems all right, continue troubleshooting using the steps regarding flickering/switch issues.


    1) Clean the internals of the light
    Use compressed air or “tap and blow” to make sure no metal shavings/debris from the manufacture of the metal parts is caught inside the tube.

    2) Check the contact between body and tailcap/switch-assembly

    img src: http://farm4.static.flickr.com/3458/3398710206_f9ed098301_o.jpg

    Remove the tailcap and use a paper-clip or otherwise suitable piece of metal and make contact between battery negative and the body. Make sure you make the contact on a part of the body that is not anodized. If the flickering stops, this may indicate a “bad” switch or bad contact between tailcap and body. Use a pair of needle-nose pliers (or a pair of sturdy tweezers) to tighten the switch-assembly (turn clockwise). If the switch-assembly is tight in the tailcap, remove it (counter-clocwise) to inspect.

    img src: http://farm4.static.flickr.com/3592/3398720714_e446292879_o.jpg

    Some switches are “open” (MTE “P7-D”) while others are “closed” (Romisen RC-F4). If your switch is of the “closed” type, it will hold the switch within a container that is inserted into the tailcap. If it is “open” the tailcap itself will form the container.

    img src: http://farm4.static.flickr.com/3664/3398659792_426d248b92_o.jpg

    For “closed” switches, tighten the inner seal (see picture), reassemble and test. If no improvement is seen, continue with procedure for “open” switches.
    For “open” switches, remove the parts and check for contact. Use a fine-grain sanding-paper (400 grit or higher) to clean the contact surfaces for solder-flux and other impurities.

    img src: http://farm4.static.flickr.com/3432/3398733304_75989f44c1_o.jpg


    3) Check the contact between body and pill.
    Do the paper-clip test as described previously. Vary the pressure on the battery. If the flickering is reduced/stops when pressure is applied, this indicates a contact problem between the pill and the body.
    Get access to the pill by removing the head or by removing the bezel/lens/reflector. Remember to NOT touch the "shiny" parts of the reflector with your bare hands (or anything greasy)

    img src: http://farm4.static.flickr.com/3633/3397936553_9484783d9a_o.jpg

    Check if the pill is tight by using a pair of tweezers/needle-nose pliers and twist it clockwise. If it is tight there may be a problem with the wiring, which requires advanced repair (perhaps to be covered in another thread).
    Reassemble and you're done.

    img src: http://farm4.static.flickr.com/3608/3398754918_53a03fb7ba_o.jpg

    I hope this is helpful. I searched these forums for help on my MTE “P7-D” as it was nearly unusable when I got it (heavy flickering) and there was no easy check-list for troubleshooting these lights. Here it is! Feel free to comment!

    Flashlight issues~https://tinyurl.com/bw2d3pd
    DX Return Policy/Warranty~https://tinyurl.com/yb7dpg3s
    New customers read this ~ http://tinyurl.com/3kcyfqm
    Tracking site ~ http://www.17track.net/en
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    mod edited (cyclist) on 1/16/2011 at 7:35 PM
  • chrisandhiace Monday, January 17, 2011 3:24 AM Reply
    Great stuff!....one other problem I've had (numerous times) is poor / sporadic contact between the circuit board negative outer ring and the pill itself
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  • DrJones Monday, January 17, 2011 1:08 PM Reply
    While that is valuable information, it's a bit questionable to copy texts/images from elsewhere without asking the authors beforehand. "if you're reading this and object" is not really the legitimate procedure...
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  • TNprime Tuesday, January 18, 2011 4:55 PM Reply
    Dr Jones, great contribution to this helpful thread. GREAT! What is so 'questionable'? Are you new to the internet? Do we have to follow MLA procedures?

    And OP honestly thanks for posting even IF the boys and girls at CPF didnt know you used their info, I know you were being altruistic in posting and passing along this advice. You helped me solve a problem I have been having and never would have thought to look for a place such as CPF.
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    post edited by TNprime on 1/18/2011 at 4:56 PM
  • DrJones Tuesday, January 18, 2011 6:13 PM Reply
    You're welcome, I always like to contribute. :)

    No, I'm not new to the internet, I use it since the days of NCSA Mosaic.
    You seem to think the internet is a world where everything belongs to everyone.
    (All your information are belong to us? :)

    And it's worth noting whom you thank for that helpful information: not the author who spent hours writing it...
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  • TNprime Tuesday, January 18, 2011 7:21 PM Reply

    from the OP....
    "Thank you to nakamoomin/Tom for making this post on CPF, if you're reading this and object to it being on DX, please let us know. "

    and DrJ, I too have been around since the days of 300baud dial up bulletin boards and such, remember placing the phone into the modem? even so, and regardless, re-read my post.

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  • DrJones Sunday, January 23, 2011 8:32 AM Reply
    I said "...whom you thank..."
    There's a difference between thanking the author or thanking someone who thanks the author, and that even in a way that the author probably won't even receive those thanks.

    Yep, a 300 baud acoustic coupler was my starter drug, too.

    I re-read your post as you suggested... MLA is about citing articles, not about copying them. I guess you didn't refer to that though. What do you think did I miss in your post?

    Do you really think it's ok that any forum/website may copy any post/article/images from any other forum/website without asking? CPF is not Wikipedia.

    Copying an article without asking/permission is against common sense.
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  • popoyaya Tuesday, January 25, 2011 2:04 AM Reply
    One day this will be a civilized and co-operative planet and all knowledge will be freely available to all!
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  • sheepish Top 10 Forum Poster Tuesday, January 25, 2011 5:19 AM Reply
    Why is that CPF thread members only?
    Remembering 30 years.
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  • DrJones Wednesday, January 26, 2011 4:01 AM Reply
    As far as I know, a mod moved it to the budget-light forum, because it refers to budget lights, and that sub-forum is member-only.
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