Results 1 to 10 of 10

Thread: Power problem on led light strings

  1. #1
    Join Date
    Dec 2013
    Location
    Kenai, Alaska
    Posts
    72
    Post Thanks / Like

    Default Power problem on led light strings

    Iím going on 5 years with about 200 Color-Rite led light strings that are used on my wire frame figures that I have built. Last year I noticed that a handful of strings were not as bright as the other strings on the figures. (This was especially noted on the blue led bulbs in the strings ÖÖ these strings allow you to interchange bulbs of various colors). I replaced the strings and everything was fine. In diagnosing my problem strings I noted that the voltage output was 1.75 volts. I then tested some new strings I have and found that they output anywhere from 2.70 volts all the way up to 3.0 volts. Since all the bulbs still work on the 1.75 volt strings (they are very dim) Iím wondering if my male 120 volt plug (picture attached) has some how allowed this to occur while trying to drop the voltage down to the desired 2.7 - 3.0 volt output. If so, I would rather replace the plugs (but I havenít found anything yet online that might work) rather than replace the entire strings when in reality the led bulbs still work. Not to mention the time it takes to unwrap and rewrap the wire frames and the cost of new strings.

    Any suggestions would be appreciated.

    Thank you.
    Attached Images Attached Images

  2. #2
    Join Date
    Oct 2014
    Location
    Sauk City, WI USA
    Posts
    1,085
    Post Thanks / Like

    Default Re: Power problem on led light strings

    Your plug is most likely not the problem. It mostly likely just has a fuse in it with no other electronics. Most LED strings have a "blob" that is where the change from AC to DC is done. Inside the blobs will be either a bridge rectifer setup or a resistor of some kind. The power is usually passed along to LEDs with each one taking a piece of the voltage until there is none left. That blob is set up for the number of LEDs that are in each string. Long strands of lights (like yours) might have multiple blobs that control that part of the string.

    Where did you measure the output voltage? If you change the resistor or the bridge rectifier, you can adjust the amount of voltage. The AC plug probably is not involved.

  3. #3
    Join Date
    Dec 2013
    Location
    Kenai, Alaska
    Posts
    72
    Post Thanks / Like

    Default Re: Power problem on led light strings

    I would agree with you that the AC portion of the plug most likely is not the problem. The AC plug not only is fused as you suggested but when I disassembled it today I was able to access the ďblobĒ as you described which was located inside of the AC plug housing. (see attached photo) I measured the voltage right where the ďblobĒ connects to the wire for the lights and that is where I was getting 1.70 volts on the poorly performing led strings. Iím not sure what Iím looking at in the photo Iím guessing that I have some type of resistor set up. There really isnít much to this board. Is it possible to build one or modify my bad boards?
    Attached Images Attached Images

  4. #4
    Join Date
    Dec 2012
    Location
    Hudson MA
    Posts
    3,702
    Post Thanks / Like

    Default Re: Power problem on led light strings

    That is a half wave bridge rectifier. The blob is a capacitor. The corrosion is one potential problem. However, I suspect you have a bad socket somewhere in the string.


    2019 - Just moved into a new home (yet another change of plans). Will be dim but not dark. Too much to do at the new place to leave time for a show.
    https://www.youtube.com/channel/UCyX...ttrsZNARkUce0Q

  5. #5
    Join Date
    Dec 2007
    Location
    Maryville, TN
    Posts
    241
    Post Thanks / Like

    Default Re: Power problem on led light strings

    Corrosion is the first thing to fix. Clean it off using soap and water using a toothbrush.

    Let it dry for several hours then reassemble and check the output voltage again.

    Dennis
    Inventor of the "LED Keeper"

    My Videos [URL="http://www.vimeo.com/Dennischerry"]www.vimeo.com/Dennischerry[/URL]

  6. #6
    Join Date
    Dec 2013
    Location
    Kenai, Alaska
    Posts
    72
    Post Thanks / Like

    Default Re: Power problem on led light strings

    I'm not sure that my picture did justice to the problem I'm trying to figure out. I believe what you think is corrosion is actually white silicon that was used by the manufacturer to seal up both ends of the board as it was placed in the plastic housing. It has been tough to remove all of that from the ends of the board. When I look at the board under the magnifying glass, I don't see any corrosion of the board. Just white silicon.

    If I did have a bad socket in my strings, I guessing that would be had be rather time consuming to find. But hey, at least I'm still learning in this process.

    Thanks for all of the replies.

  7. #7
    Join Date
    Dec 2012
    Location
    Hudson MA
    Posts
    3,702
    Post Thanks / Like

    Default Re: Power problem on led light strings

    You can use a needle probe at each socket to see if you get the desired voltage progression. One probe stays at the plug and the other probe is moved from socket to socket. A large change indicates the previous socket needs to be cleaned.


    2019 - Just moved into a new home (yet another change of plans). Will be dim but not dark. Too much to do at the new place to leave time for a show.
    https://www.youtube.com/channel/UCyX...ttrsZNARkUce0Q

  8. #8
    Join Date
    Dec 2013
    Location
    Kenai, Alaska
    Posts
    72
    Post Thanks / Like

    Default Re: Power problem on led light strings

    That sounds reasonable. I'll start checking the wire frames this week that have the problem strings and see if that does the trick. I've got 40 frames to sort through and report back once I have a chance to check the voltage as you suggested.

    Thanks for the suggestions.

  9. #9
    Join Date
    Dec 2016
    Location
    Anchorage, AK
    Posts
    297
    Post Thanks / Like

    Default Re: Power problem on led light strings

    That is indeed a half wave rectifier. The diode is the only active component. I find at work that if the resistors and that type of capacitor look undamaged, it is the active component that has an issue. I would replace the diode. You could unsolder it and get the Part# off of it and replace (Probably starts with 1N100?) If I knew the max current supported I could reccomend a part. I could mail you one if not available in your area, as your not far from me. Or send me the board and I will replace it for you. I'll PM my address.

    FYI blue leds ususally have the lowest lumen (brightness) output compared to the other colors, if you look at the specs.
    Last edited by aknflyer; 09-24-2019 at 02:06 AM.

  10. #10
    Join Date
    Dec 2013
    Location
    Kenai, Alaska
    Posts
    72
    Post Thanks / Like

    Default Re: Power problem on led light strings

    Thanks for the offer. I sent you a PM.

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •