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Ferrite Bead Impact on PCB Board

12/10/2015 10:44 PM

Dear Friends,

I Have removed ferrite bead from the PCB whose supply is 12 VDC.

The system is working fine for now. can anyone tell the impact of this in future.

I am assuming that the system can function without ferrite beads.

Request your advice.

Regards,

M.Boopathy

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#1

Re: FERRITE BEAD Impact on PCB Board

12/10/2015 10:49 PM

Don't eat the bead.

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#2

Re: FERRITE BEAD Impact on PCB Board

12/10/2015 11:29 PM
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#3

Re: FERRITE BEAD Impact on PCB Board

12/11/2015 12:55 AM

The bead is usually there to suppress high-frequency electrical noise. It might affect the EMI/EMC profile of the equipment and cause more interference to nearby equipment or it might be in the circuit to dampen some high frequency oscillation leading to excessive noise on the output or it might be there to eliminate ringing in logic circuits so now the circuit will not operate correctly or it might be unpredictable although everything may be working fine now, a temperature change might affect the circuit just enough to cause erroneous operation.

I guess it would be too much to ask to get a schematic of the circuit and show which bead was eliminated or even a photograph of the circuit board and we might even be able to deduce the reason the designer spent time and money to put it in there in the first place.

Be sure to remove the grounding prongs on all your power cords. The equipment will still probably operate just fine without them, most of the time.

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#13
In reply to #3

Re: FERRITE BEAD Impact on PCB Board

01/20/2016 12:37 PM

"... there are things that we now know we don't know. ..." e.g. there are circuits whose output or input would appropriately be input or output to peak-pulses or even µ-level frequency bands or just function or function a lot better without such presented there

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#4

Re: Ferrite Bead Impact on PCB Board

12/11/2015 9:23 AM

The ferrite bead is there to filter unwanted and harmful noise out of the circuit.

Depending on where the device is used it may become very unstable without the filter.

Most computer and high speed electronic devices have components that are triggered at .3 to .7 volts which makes their circuitry very sensitive to any/all induced voltages greater than .3 volts.

If the device is controlling a critical process your removing the ferrite bead could result in a runaway condition that might be fatal.

If it is just a toy or personal device doing so will not present any danger to the user but the device will most likely not perform at a satisfactory level.

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#5

Re: Ferrite Bead Impact on PCB Board

12/12/2015 12:19 PM

I am fascinated as to know why someone, who has not a clue for what a/any component is used for, simply removes it and then asks us here why it was there.....

The word "moronic" does not even start to describe it!!

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#9
In reply to #5

Re: Ferrite Bead Impact on PCB Board

12/14/2015 11:08 AM

It is better called *ignorance* -- and the questioner is here for an answer.

As has already been mentioned, (we don't know where in the equipment the "bead" is installed) this was probably added to meet EMC requirements, not a functional matter at all, but a legal one; "Can we sell it?"

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#10
In reply to #9

Re: Ferrite Bead Impact on PCB Board

12/14/2015 11:27 AM

A "clever" Newbie would do it very differently, he would ask for example:-

"What does this Ferrite bead do on this PCB? Why is it there?"

Not take it off and then ask.......

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#6

Re: Ferrite Bead Impact on PCB Board

12/12/2015 9:08 PM

This sounds like a misapplied sandblasting technique--"impact of ferrite beads".

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#7

Re: Ferrite Bead Impact on PCB Board

12/13/2015 5:37 AM

The ferrite bead is a bidirectional high frequency AC blocker. It is seen as an added inductance, so very sharp-fast rise time signals are attenuated. Larger ferrites are good for lower frequencies.

Most common use is to block the odd-order harmonics from switching power supplies from entering the powered equipment - which wants pure DC.

Switchers make abrupt square waves, and as you know a square wave is the infinite sum of all odd order harmonics

These harmonics can reach broadcast frequencies and interfere with reception in fringe areas - adding noise to the received sound or signal. In addition, many countries require radiated noise to be below a statutory level - US = FCC rules, because 50 million radiating sources raise the noise floor. Short wave reception is bad in cities for this reason

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#8

Re: Ferrite Bead Impact on PCB Board

12/13/2015 5:54 PM

I Have removed ferrite bead from the PCB whose supply is 12 VDC.

Why?

I am assuming that the system can function without ferrite beads

Again, why are you removing a part from someone else's circuit board, especially when you don't know the potential effects?

....

Put it back, it's there for a good reason (warranty for a start, but you have already voided that when you modified the board).

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#11

Re: Ferrite Bead Impact on PCB Board

12/14/2015 11:33 AM

I've been working as an EMC engineer for over 30 years, a second career from which I'm now mostly retired. In my experience, whenever I saw an added ferrite (or had to add one) it was often a desperate measure at complying with a legal limit on radio interference (EN 55022, say or FCC Part 15) without which the equipment could not legally sold. In the US, noncompliance could subject users, sellers, shippers or manufacturers to hefty fines for each non-compliant unit on the market.

See, for example, https://transition.fcc.gov/eb/News_Releases/DOC-263862A1.html

Best leave it in there -- or run the EMC test with it installed and with it removed to see if the ferrite is really needed. Even if other users of the radio spectrum are clueless, there are in the US many competent technicians and engineers in the business of providing radio communications -- and tens of thousands of Amateur Radio operators (I'm one) who can and do detect, locate and report sources of interference

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#12
In reply to #11

Re: Ferrite Bead Impact on PCB Board

12/14/2015 2:57 PM

The ferrite bead is there to prevent visitation by HLS, in order to enforce FCC rules. It also prevents your hair from standing on end while using your cellular device.

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