Portable Lamp Repairing - Optical switch

Thread Starter

Rata3000

Joined Mar 20, 2019
6
Good day!
I'm trying to fix a portable lamp. It is powered by means of a USB-C cable. It has a battery and a photoelectric switch. The light is provided by a 54 LED units strip.
Lamp info:
https://flos.com/products/table/bon-jour/bon-jour-unplugged/#full-overlay-product-popup

The lamp fell off and hit the floor. After that, it does not turn on the LEDs

I have opened it and tested with a multimeter. I cannot get anything clear. There is 5V voltage difference between battery connectors and also between light plug pins. Still, the light won't turn on.

The LED strip turns on when a 9V current (from a different source) is applied. When a 5V-2A power from a mobile phone charger is supplied it does not turn on. How can I know what voltage is needed?

Please, find attached pictures.
How could I begin with to localize where the problem is?

Thanks a lot in advance!

IMG_20190321_011300.jpg IMG_20190321_011402.jpg
 

oz93666

Joined Sep 7, 2010
737
The lamp is listed as 2.5W , which is quiet low , so in this case the manufacturers figures may be correct ....

The leds should consume about 2W , so if you have meters , measure the current and voltage when leds are fed with your 9v supply ... current x voltage is power , if the supply is 9V a good current is 200mA ...
 

Thread Starter

Rata3000

Joined Mar 20, 2019
6
The lamp is listed as 2.5W , which is quiet low , so in this case the manufacturers figures may be correct ....

The leds should consume about 2W , so if you have meters , measure the current and voltage when leds are fed with your 9v supply ... current x voltage is power , if the supply is 9V a good current is 200mA ...
OK!
With labeled 9V power supply current measured in multimeter is 410mA.
Measured 9V-power-supply voltage is 11,7V
Gives a 4.6 W power.
 

Thread Starter

Rata3000

Joined Mar 20, 2019
6
The battery gives 3.7V
The USB cable gives 5V
Looks light the LED needs around 9V to turn on... How can this be possible? Could it be a voltage converter "somewhere" in the circuit board?
Sorry, a Civil Engineer here... not that much into electronics (yet...).
 

TrmickCO

Joined Oct 9, 2016
72
Anytime a device has a hard impact and stops working, I'm looking very closely at loose joints and using my continuity tester. I agree, it is strange that it now has higher power requirements after a a hard impact.
 

Thread Starter

Rata3000

Joined Mar 20, 2019
6
Some corrections and further info:

-LED strip turns on around 6,9V. Maximum voltage applied with my 9V power source is 8,5V and current is 230mA (around 2W).
Previous measures were inaccurate.
-U3 is
TPS61500
High Brightness LED Driver with Integrated 3-A, 40-V Power Switch

http://www.ti.com/product/TPS61500
@sghioto -- you were right!
-Voltage on the LED connection socket is ~4.5, not enough to turn on the lights.
My guess: there is something wrong with the optical switch so it doesn't send the signal to the U2 microcontroller to turn on the lights.
What do you think? How could I find the malfunction?
 
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