Help identify ferrite bead on a sound card

Hi,

ferrite beads are not useful for audio frequencies.
Thus I rather guess they are used in the power (including GND) path.
Maybe it is used to connect A_GND with D_GND.

In either case it is used for HF frequencies in the high MHz.
And the circuit will probably work if the ferrite bead is replaced by a piece of wire. (for sure it is recommended to install a ferrite bead).

Ferrite beads are rather low impedance at DC (low milliOhms), and they may go up to several 100 Ohms at many Megahertz. They are no precision devices, they are not critical.
So as long as they can carry the DC current you need .... you may chose a bead with some tens of Ohms at high frequencies.

Klaus

Ferrite beads at audio I/O connectors are most likely there to keep EMC standards, no necessarily required for repair.
You can select ferrite bead by size. Most manufacturers don't have more than 2 or maximal 3 different ferrite materials for beads on leads, you can choose the material with highest impedance.

KlausST said:

Hi,

ferrite beads are not useful for audio frequencies.
Thus I rather guess they are used in the power (including GND) path.
Maybe it is used to connect A_GND with D_GND.

In either case it is used for HF frequencies in the high MHz.
And the circuit will probably work if the ferrite bead is replaced by a piece of wire. (for sure it is recommended to install a ferrite bead).

Ferrite beads are rather low impedance at DC (low milliOhms), and they may go up to several 100 Ohms at many Megahertz. They are no precision devices, they are not critical.
So as long as they can carry the DC current you need .... you may chose a bead with some tens of Ohms at high frequencies.

Klaus

Click to expand...

Thank you so much for your kind reply

you are right this component would probably have a very low impedance at audio frequencies anyway...

I will go to digikey and choose a ferrite with similar dimensions and something like 50 to 100 ohm at 100 mhz

all the best

Nuno

FvM said:

Ferrite beads at audio I/O connectors are most likely there to keep EMC standards, no necessarily required for repair.
You can select ferrite bead by size. Most manufacturers don't have more than 2 or maximal 3 different ferrite materials for beads on leads, you can choose the material with highest impedance.

Click to expand...

Thank you so much for your kind reply

Indeed looking at the frequencies this devices are rated to they are almost a short at audio frequencies...

I will go to digikey and choose a ferrite with similar dimensions and something like 50 to 100 ohm at 100 mhz

all the best

Nuno

Do you know if the parts were not populated by OEM or depopulated by someone for sure?


If so, circle the pads and attempt to duplicate the partial schematic. For audio the main purpose is to reject AM signals from getting demodulated into audio or SMPS ripple filter near 1 MHz, high impedance 805 parts maybe with > 500 mA

Below is 8 kohm at 100 MHz LC resonance and 0.7 ohm at DC, so you can compute the LC values.

D.A.(Tony)Stewart said:

Do you know if the parts were not populated by OEM or depopulated by someone for sure?


If so, circle the pads and attempt to duplicate the partial schematic. For audio the main purpose is to reject AM signals from getting demodulated into audio or SMPS ripple filter near 1 MHz, high impedance 805 parts maybe with > 500 mA

Below is 8 kohm at 100 MHz LC resonance and 0.7 ohm at DC, so you can compute the LC values.

View attachment 190744

Click to expand...

Hi!
Thank you for the help

They have been tore alright... pictures of this sound card on the internet clearly show them
7 ferrites, some pads went along with them .. fortunately the vias seems to be intact and they only connect on the back
I have no idea why... this component doesnt have any copper or precious material.. maybe someone needed them for something else
I really would like to bring this little bugger back to life, there are also a few traces broken on the back

OMG I found the schematics online on VOGONS




Amazing I love the internet
I will take a look and maybe I will have some clear picture now

EDIT: They seem to be .850 to 1 microHenry

I am reading they are all 47 uH, but no details were give. They would be the same size as 1/4 resistors, but you can also choose 805 SMD packages.
No idea on DCR values.

D.A.(Tony)Stewart said:

I am reading they are all 47 uH, but no details were give. They would be the same size as 1/4 resistors, but you can also choose 805 SMD packages.
No idea on DCR values.


View attachment 190775

Click to expand...

Thank you Tony

I have read on VOGONS that one of them was tested to .850uH and on some schematic it was stated 1uH
It is very confusing, my skill level usually falls back to replace capacitors and resistors...

So 47uH will make it 30k ohm at 100 mhz... that's rather high no ? I have not seen such component on digikey...

Z = 2 * Pi * 100mhz * 47x10-6 ... am I wrong ?

I just have the feeling that if i dont replace it with the right value there will be noise on the audio output... and yeah this is a SOUND card

thank you

It is not a ferrite bead (FB) but it is used to comply with FCC Part B to reject IDE logic transition noise up in the 100 MHz range so that when external linear power amps have non-linear effects with RF, the demodulation interferes with the audio signal.

The datasheet has a BOM , or "bill of material" for this shown in >/AS100-L-M S100DM2.pdf file near the end, p6-12, as I showed.

It says it is an epoxy thru-hole 47 uH inductor, and L is the reference designator (REF DES) for inductor. Guess what it is for ferrite bead? It could be identified as FB# or could be L . The 1st example I found in their documents was in the ALS100 folder is shown below.

( except I could not read the .doc files made by Adobe Framemaker)

It will work with a jumper on the SMD pad, until you get some inductors.

In fact, it is the only BOM in your link of manuals with an L5, many others have L1 to L4 of 10 uH.
FB's are cheaper lossy ceramic materials with a mix of metal, magnetic and dielectric to simulate a lossy inductor with fairly low R but much looser tolerances.

Considering my background , and others here (read) and yours, why would you doubt my previous answer compared to your online search?

I too love these Win95 vintage audio synth cards. Win95 from Packard Bell had a huge suite of useful features, speakerphone, modem, VOIP, phone auto message folders, custom voice messages, MIDI music synth, and DC coupled electret mic inputs with no pop sound or DC offset instead of the cheap AC coupled types now.