Where can you buy them ,EMI filters

Digi-Key is a great place to buy them. It is one of the most popular and best places to source components. But there is a minimum shipping charge of like $7. It is fast shipping though,for me 2 days… in the USA. The components themselves are usually 20 cents or something if you buy a few.

If you know what frequency filter it is,then search it by that on the website. 120hz and 240 hz is typical. This means that when electricity is super high frequency,it starts to be converted to heat. Normal dc current is able to flow through with minimal resistance(resistance of current flow). I don’t know much about them,but you definitely want to check some schematic. You can’t really test it to see what frequency it starts to impede current flow(resist=impede).

It also acts as a fuse generally,since those filters are tiny and can’t handle much current. Should a voltage spike or short happen that causes lots of current flow,the filter burns out. You could use a jumper wire instead,since the emi noise probably won’t cause it not to work,but if something happens again on that line,it would damage other components instead of probably that filter alone..