Nhật Tảo is a busy market so the best time to go there is in the late morning or early afternoon on weekdays or Saturday because some shops might close on Sunday.
These electronic components are made in China partly. So the price is really cheap!
If possible, go with someone who speaks Vietnamese, which is good for bargain and translation. The shops will accept Vietnam dong (VND) only and in cash.
Where is it?
Here is the map: https://goo.gl/maps/Ufa5XZ9wmR42