trying to repair my daughters night light

Thread Starter

me217

Joined Apr 23, 2016
13
hey everyone first post here, still learning about circuit boards. I'm after a bit of help repairing my daughters night light. 3 of the 9 LEDS are flickering when its on.



the labelled LEDs 1-3 are the green ones which are flickering.


the one the screwdriver is pointing to is LED 1.
the other LEDs are Red and Blue. they all work fine but the Green flickers or sometimes doesn't even work. the power comes to that board from another board which just has some caps and resistors on it. if needed i can put up a picture of it. but I'm almost certain that isn't at fault.
 

GopherT

Joined Nov 23, 2012
7,983
@me217
Touch a soldering iron to the two solder pads of the Green LED and the 0 (zero) ohm resistor next to it. Then touch the soldering iron to the three pads of the transistor Q1 which controls the green LED.
 

Thread Starter

me217

Joined Apr 23, 2016
13
are
@me217
Touch a soldering iron to the two solder pads of the Green LED and the 0 (zero) ohm resistor next to it. Then touch the soldering iron to the three pads of the transistor Q1 which controls the green LED.
are you thinking there is a bad connection in the solder? i'll give it a shot as soon as the iron heats up.
 

Thread Starter

me217

Joined Apr 23, 2016
13
just gave it a shot. no luck, i also forgot to mention that the numbers are the order from worst to best as far as flicker goes. number 1 flickers quite badly two not as much and 3 not much at all.

EDIT: i was wondering if its a voltage drop. also they don't seem to flicker until they hit full brightness, as they fade on and off in sequence. i have heard that different coloured LEDs require more power then others. Would green require more then red and blue.
 
Last edited:

GopherT

Joined Nov 23, 2012
7,983
The LEDs are still good if they are lit. There is a bad connection somewhere upstream. If the bad connection is under the black glob of black epoxy, then you may as well buy a new night lite.
 

Thread Starter

me217

Joined Apr 23, 2016
13
The LEDs are still good if they are lit. There is a bad connection somewhere upstream. If the bad connection is under the black glob of black epoxy, then you may as well buy a new night lite.
yeah, its not locking good. the other board receives 6VAC which directly runs a motor and then is converted to DC for the LEDs. would the oven reflow trick be worth a shot?
 

GopherT

Joined Nov 23, 2012
7,983
yeah, its not locking good. the other board receives 6VAC which directly runs a motor and then is converted to DC for the LEDs. would the oven reflow trick be worth a shot?
Yes but watch it closely. No need for smoke alarms ringing at thus hour.
 

SLK001

Joined Nov 29, 2011
1,513
yeah, its not locking good. the other board receives 6VAC which directly runs a motor and then is converted to DC for the LEDs. would the oven reflow trick be worth a shot?
Not after the IC is "globbed" over with epoxy. The expansion of the epoxy can rip the bonds off their pads.

Actually, a better high-resolution picture of the backside of the board (the "green" side) would help with the diagnosis.
 

Thread Starter

me217

Joined Apr 23, 2016
13
well its "fixed" now. and i use that term very loosely. i rewired it so it just stays on solid blue. i got a feeling that the transistor right near the power input is faulty. after cooking it. as it flickers on and that's it. ah well. win some you lose some. thanks everyone for the advise
 

takao21203

Joined Apr 28, 2012
3,682
The efficiency isnt good.

The advertised product most likely will pulse LEDs
Even some USB output converters can be hacked. For more than 5v !
Without the usb socket these are small.

But they cant do 40v or 60v. Its about the limit what is safe, like the voltage used for the analog telephone system.

For real illumination you need a larger solar cell and probably a lithium battery. These solar lights from shops are just dots, and the cheap ones will suffer from rusting after a short time. Theres a lot of trash in the shops..
 

hp1729

Joined Nov 23, 2015
2,304
just gave it a shot. no luck, i also forgot to mention that the numbers are the order from worst to best as far as flicker goes. number 1 flickers quite badly two not as much and 3 not much at all.

EDIT: i was wondering if its a voltage drop. also they don't seem to flicker until they hit full brightness, as they fade on and off in sequence. i have heard that different coloured LEDs require more power then others. Would green require more then red and blue.
The blue requires a higher voltage. Nothing special about the green. How is your confidence on buying and changing LEDs and transistors?
 

Thread Starter

me217

Joined Apr 23, 2016
13
The blue requires a higher voltage. Nothing special about the green. How is your confidence on buying and changing LEDs and transistors?
I would probably better off building a new board. Then trying to repair this one. I'd like to. I wonder if I could use some RGB LESs and have them go through the colours
 
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