No, it's not normal for Bitmains PSU since you are using a Chinese PSU I don't know how this PSU works.
Usually that kind of issue it's due to leak or maybe have broken capacitor if you have a multitester that could read capacitor from your PSU you can check those broken capacitors.
The multimeter that I use looks like this
![](https://ip.bitcointalk.org/?u=https%3A%2F%2Fi.imgur.com%2FZEh2Djx.png&t=662&c=zHvh2YEn_WGA9Q)
You can replace that broken capacitor with the same value.