LED Strip CB - blue always on, even turned off

Thread Starter

urootsr

Joined Mar 31, 2020
3
Hello,

I dont know what the problem is, I think something is broken (short circuit).
If I turn the LED‘s of, blue is on. If i turn it on, everything works (can change the colours etc), but blue is always on. Only green or red not possible.

can you help me finding the problem?C7B96BD7-CC4C-49C4-8417-C524B6CCECB8.jpeg
 

Reloadron

Joined Jan 15, 2015
5,501
If I had to guess, which I am guessing, it looks like a MOSFET drives each LED output. My guess is either a shorted MOSFET or a MODFET constantly gated on for some reason. Bottom of the image on the right above the terminals. Those 3 components look to be the MOSFETS driving the RG & B leds.

Ron
 

Thread Starter

urootsr

Joined Mar 31, 2020
3
Thank you for your answer!
I tested with a multimeter and I think you are right;

I want to buy new mosfet, but I have no Idea which one.
Looked at ebay and found the name „sot-23“. But n-channel or p-channel, 4,3 A or 5A? My LED-Stripe is 10m with 2 inputs.
 

Reloadron

Joined Jan 15, 2015
5,501
In the past I played around with some 5050 LED strips which were common anode 12 volt. Since they were common anode I used an N Channel MOSFET on a breadboard. I used FQP30N06L MOSFETs which are just every day logic level mosfets but were in a TO220 case, not surface mount. This is what my setup was.

5050 LED String.png

You don't need much as to current and inthe above, while it worked fine, it was severe overkill.

Ron
 

Wolframore

Joined Jan 21, 2019
1,748
Smd XORB is Chinese copy of AO3400A

1585672052229.png

1585672323403.png

The one in the middle of the picture suspected bad... not impressed with the design or soldering. No inrush limit to gate.

your video confirms that one is one big short!
 
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