Christmas lights repair + schematic explanation - Noobie - Page 1
Forum section: electronics / repair

author: fagouma
author_rank: Contributor
timestamp: December 13, 2017, 12:11:28 pm
content: Hello to the community.As i am in the search of new experiences with electronics repairs, i decided to fix some christmas lights. As i am noobie, i can always learn sth from as silly as this.Facts : - lights work of AC. No AC to DC converter or box with "modes".They plug directly to mains power. (Greece = up to 250volts)- They are "socket style", meaning you can connect more lights (if u have) in the "tail", cuz there is a socket.- I get full volts at the "tail" socket, but no lights at all.- I draw a simple schematic in order to explain to me how i should measure and what.It shows how they are connected. I have areally cheap multimeter until Dave shows on youtube a sub 50 dollar suggestion. Then maybe i could buy one in that price range.Schematic:https://www.dropbox.com/s/wqrqux81hawlw3x/Screen%20Shot%202017-12-13%20at%2013.44.14.png?dl=0

author: Kilo Tango
author_rank: Regular Contributor
timestamp: December 13, 2017, 01:45:50 pm
content: The cct you have drawn shows a line bridging out the LEDs this means they will never work, so check your cct.Without something across the small socket the LED's will not light, should there be a controller there ?. How many LED's are there ?, only 5 ?.learning on things that plug into the mains is really not a good idea.DVM. if you are going to measure mains voltages you need one that is safe for the voltages you are measuring.Ken

author: fagouma
author_rank: Contributor
timestamp: December 13, 2017, 02:03:30 pm
content: Quote from: Kilo Tango on December 13, 2017, 01:45:50 pmThank you for your answer.Here's the new schematic.https://www.dropbox.com/s/rhp7i49py04s7ru/Screen%20Shot%202017-12-13%20at%2015.56.16.png?dl=0Does it make a difference?The lights are not 5 obviously. There are more, like 90 to 100. I did 5 just to show the connection.I know it's not a good idea but it's knowledge nonetheless.Edit : They are not led lights. They are incandescent small lights. You know, with a tiny wire inside them.

author: Kilo Tango
author_rank: Regular Contributor
timestamp: December 13, 2017, 02:36:38 pm
content: Your diagram still doesn't make sense, sorry, it still appears to bridge out most of the bulbs. Is this line going direct to the add on socket perhaps ?. For current to flow there has to be a complete circuit between the mains live and neutral. Your diagram suggests that the live ( NOT +) feeds the bulbs and stops at the socket and the neutral ( NOT -) feeds the bottom of the socket only, so the current can't flow round thro the bulbs and back to the mains neutral.If the bulbs are the type that screw in, the way to fix them is to unscrew all the bulbs and check their resistance with your meter, and keep going until you find the blown one ( or 2).They are not very safe and not allowed in the UK, because if you unscrew one bulb and touch the contacts you will get a full mains shock.Ken

author: fagouma
author_rank: Contributor
timestamp: December 13, 2017, 03:04:10 pm
content: Quote from: Kilo Tango on December 13, 2017, 02:36:38 pmThanks again for your reply. This is the way they are connected. For sure. I just found them and thought to give it a go.I know what you mean about the connections. The lights are connected like this in a circular way. And the third wire starts from the mains socket and goes straight to the "small socket" .They are not the type that you can screw in. The lights are permanently connected with their leads.Assuming i remove one or two, what value of resistance i should see? Really big like an open circuit if it's burnt and really small if the light is alright? Would "continuity mode" work?Edit: That's why i wrote to the Subject "schematic explanation". Cuz i couldn't understand myself this connection the lights have.

author: Kilo Tango
author_rank: Regular Contributor
timestamp: December 13, 2017, 03:58:55 pm
content: Hi, if that's the way they are connected they will not work, as I said the current can't flow round the circuit, there is a hole !. Something missing ?.Resistance mode or Continuity. Continuity means how well does it conduct or the inverse of resistance !.If you measure the resistance it should be fairly low for a working bulb and high for a blown one. However some of these had a resistance built into the base so a blown bulb didn't stop the string from lighting.Trouble is if you cut in to get to the bulb terminals, that will damage the insulation and so its not safe to use afterwards. To learn its OK, just be aware that they can't be safely used afterwards. sticky tape is not a suitable replacement for an insulator, wire ends can poke thro.Ken

author: fagouma
author_rank: Contributor
timestamp: December 13, 2017, 04:34:54 pm
content: Thank you for your answers Ken. I' ll see what i can do.

author: PA4TIM
author_rank: Super Contributor
timestamp: December 13, 2017, 09:49:14 pm
content: QuoteContinuity is a function that looks if there is a low resistance connection between 2 points. Not the inverse of resistance. That is called conductance and measured in siemens (or the old term: mho)For the rest, I have no clue what you want with those lights. Your schematic with LEDs will not work (also not with lightbulbs) the circuit is open and you short the lights.

author: ArthurDent
author_rank: Super Contributor
timestamp: December 14, 2017, 08:58:13 pm
content: Recheck the wiring to see if it is actually like this attached diagram.