Christmas light controller board fried.

Thread Starter


Joined Nov 27, 2019
Hi. I’ve only just joined this forum. After a bit of advice. I was just unpacking all the Christmas lights and remembered I accidentally broke the other half’s favourite lights ( 15 years old ) used the wrong power supply 12v instead of 6v. Was kicking myself. The controller pod smelt lovely immediately after. I have opened it up to have a look but not sure what to check.. one of the transistors had lost a corner But only 1, I dont get any lights on.
the set has has a string of stars that are made of bi-colour LED’s, each star phases from one colour to the other slowly.
every other one is the same. Red/Blue. Green/yellow. Red/Blue...etc.
I could probably just join all the wires together and make them static but that’s boring.
are there any kits or anything to replicate this or a way to repair?
I have attached photos of the controller.
any help would be greatly appreciated.


Joined Jul 11, 2016

bad design (bad PCB, -package/-case design) . . . or too high mains voltage

" 1W assuming 80°C de-rates to 1W-(80-25)·8mW≈560mW → /500mV≈1A output current " = " it's unlikely that the transistor is a bad choice"

Your image 3 shows integrated controller (the black epoxy pad) - if it's fried You're done with it


Joined Aug 21, 2008
Do you have a digital multimeter or similar instrument? If so you can check the transistors to see whether there is an undesirable short or open.

That transistor is very inexpensive -see the datasheet provided by ci139 in his post above, so you could just replace all four of them and see if that fixes it. If that doesn't solve the problem, toss the board because there is nothing else you can replace, except the controller itself, which is an option. Buy a new one and hook it up in place of the old one. Try to match up the power supply voltage and the number of LEDs.


Joined Mar 10, 2019
That black "blob" on the bottom of the board suggests there is some small micro or logic chip under it, controlling the flashing or on/off of the lights. It looks like a 8 pin (possibly 6 pin) type of chip
If it was designed to run at 6V (possibly at 5V for the chip), and you put in 12V, odds are high that "chip" is blown, and no way to repair it unless you know what it is.


Joined Jan 21, 2019
Another board easily replaced with a small microprocessor. I’m guessing it has 4 channels of switching.

replace it with a microprocessor with PWM fades you need. I would add a regulator to the circuit so it can take about 6-15v. You could even add a button and add a program feature so it can click through different patterns or speeds.

4 channels each controlling the 4 colors. If it’s just transitioning at same time it could be done with 2 channels. I believe the S8850 is a general purpose PNP doing highside switching to the LED strings by color.
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