8W 70mA LEDs Flickering - Stroboscope Effect: Possible Reasons, Troubleshooting, and Solutions

Hello, two LEDs (8W, 70mA) shone well until they started flashing like a stroboscope 1-2 times / sec. As I was not used to just throwing it away, I undressed one. No fumes can be seen. What could be the reason for such flickering?

To start with, replace the electrolytic capacitors, very often their aging and poor quality are the cause.

Ok, we'll check. Really malicious Chinese - they put in two 2,7uF / 400V electrolytes. Where did they get that value from?

The mains voltage after rectification can reach 355 V with the permissible fluctuations in our sockets.

The R3 resistor does not look fresh at all

strfind wrote:

The R3 resistor does not look fresh at all

Right, I noticed the heat until I soldered the capacitors, which have some low values, but they should be ok.
I stripped the second bulb with the same flickering and the same smd resistor is burned (!). Fortunately, I have one more functional - it easily undresses - it is 4.7 k ohm (smd 472). Is this a high voltage resistor because when I soldered a classic 4.7 k resistor it burns right away ????

How did the colleague choose the correct value of this resistor? I have a slightly different bulb and also a burned resistor on the choke. It flashes like a strobe.



The patient was a bulb with a motion sensor bought in Biedronka with a capacity of 6.5 W for 16 zlotys, of course already alive and shining. The resistor was chosen by trial and error (at higher resistances of 50 k?, it flashed more slowly). The resistor located directly behind the bridge rectifier in parallel with the choke should have a value of 1.8 - 2 k? (I tested such values and the bulb works correctly - it reacts to movement). It may be useful to someone who will have a similar fault.

I will join the topic because I have the same problem with LED DOMODO 12W bulbs. From what I see after photos, the electronic circuit is almost identical.
Symptom: The light bulb worked over two years without any problems. Now after switching on, there are a few seconds good, but later we have a stroboscopic effect, after which after a few minutes the bulb "surprises" normally for a few dozen or so seconds, after which we have the stroboscope again and again.
What has been done:
both electrolytic capacitors were replaced, ie 8.6?F / 400V per 10?F / 350V and 2.2?F / 250V at 2,2?F / 400V. Replacing the capacitors did not change the system operation at all. Then the soldering of all electronic components was corrected but to no avail. Each single LED was checked - all functional.
I do not have a "burned" element - a resistor - as in the photo of the author.
Could the JD9504sa system be the cause?
No element is heating up more than others. I do not know where to look for the cause.
Like a hot soldering iron, I will touch any element with the JD system, for a moment everything returns to normal, just as I touch the hot soldering irons of this circuit, everything is OK. Of course, for a few minutes.
I do not know where to look for a problem.

Ps. For me, the resistor on the gland is 300k? (304)

@ BC109B
Next or?

Personally, I suspect a JD9504sa scalout or smd ceramic capacitor (I do not know the original value), but none of the components bear visible traces of mechanical damage, over burns, etc.

I have seen this diagram, except that I have a lamp that is out of order.
In general, integrated circuits are used for exchange. In several LED bulbs, after replacing these systems, the bulbs regained their efficiency.