12-220V inverter fault diagnostics

[pc.alpujarra]

Hi, I have here 12-220V inverter which starts normally but turn itself off after 3 sec and red dionde on BOARD turns off. The 5V usb output from inverter works fine.
What I tried:
- I followed input power lines up to the board OK
- Fuses are OK
- Checked voltage on biggest capacitor when device on, It went up to 300-350 V (33uF,400V) but drops when red diode starts.

Where to continue?
How to check the big transformator?
Thank you

 

[Harald Kapp]

Welcome to our forum.

This failure could very well be due to overheating of some component and subsequent shutdown of the inverter to protect itself. When the red LED turns off, can you find any exceptionally hot components? Any visible clues for overheating (brown spots on the PCB or on components, bulged capacitors? Any loose parts like heatsinks?

Does this happen even without load?


(!!! caution, there may still be dangerously high voltages even if the output is turned off!!!

 

[morphingstar]

If it only takes 3 second after switching on it looks like an almost short circuit. Can you test the power semiconductors for short circuit? If these are transistors one of the Transistor Base connections may not get sufficient current, which heats up the transistor until it crashes. This could be due to a resistor in the base circuit changing its value. The temperature monitor may prevent the crash if there is enough pause between your trials.
Use an amp-meter with a big range to make sure it does not get damaged when measuring the input current.

 

[pc.alpujarra]

Hi, thank you both for replies. Did more trials.
1. Its not 3s but more likely around 5s - sorry about wrong value
The another strange think is that after start I can hear silent click - click nearly every second until red light on board turn on.

2. did not notice any excetionally hot components or smell.
3. yes it make the same even without the load
4. current on the input 12V cable 0.55A after 5s drops to 0.05 (the usb ouput works now without load) measured on negative lead
5. again I visually checked the big capacitor and when I put something straigh on top of him I can see that he does not have straight top its slightly upward going, no leaks, no cracks
thank you

 

[Harald Kapp]

Sorry, currently I do not have a useable idea. Someone else come to the rescue?

 

[(*steve*)]

Can you post a picture of the capacitor with something flat on top if it so we can judge the amount of bulge it has?