I was experimenting with my universal laptop adapter (Meind 100W) and when I switched it to 34V mode (while official max is 24V) the capacitor (25V) popped (the top opened and some white fibers spread over the nearby parts).
The capacitor is glued to the board and is not easy to remove. When using the adaptor it slowly heats now.
When under load the output voltage of the adapter drops (and probably recovers after some seconds), so I have to set it to voltage that is higher than needed.
Questions:
- Is it safe to continue using that adaptor? Can it degrage further with time or it will remain stable?
- How to unglue the damaged capacitor from board?
- Should I use some additional safety measures (for example, external capacitor connected to output) to reduce the risk? (I'm not going to just buy another adaptor)
Answer
Most likely the popped capacitor is causing stability issues (output going up and down as you described).
It should be replaced with a part with comparable voltage, ripple current, ESR and life ratings. Failure to choose an appropriate cap will likely result in the cap failing prematurely.
A properly protected power supply should not be damaged from a blown output capacitor. I wouldn't recommend operating it until the cap is replaced.
It seems odd to me that the power supply is capable of self-damage. With 25V caps the max output ought to be below 20V.
I would use a sharp utility knife to cut the part from the glue, then desolder it and replace it. Make sure you note the polarity.
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