FL3 is most definitely filtering -12V.
FL4 filters LEFT audio.
FL5 for +12V.
FL2 could be for RIGHT audio, but I did not check from another picture from backside of the PCB.

Are you sure? The line for +12V seems very very thin compared to -12V, unless -12V handles high amperage.

So, since the components in question are filters, why don't you just check connectivity with a multimeter? Find a dead one and you know the culprit - or not.

I seem to have a bad contact there. All filters are around 60~80ohms (this unimeter is lame). But FL3 is showing no connection.

Pretty sure. Here's how I came into this conclusion, do tell if I have something wrong.

I did google the header pinout and first picture of SCB-55 and my quick glance of things shows the +12V/-12V pins are 18/22 and those copper traces go through filters FL5/FL3 and diodes D2/D1 to capacitors and to what looks like voltage regulator ICs. Definitely power supply stuff. However the picture was a bit grainy so it was not so clear. I could have googled for another picture 😀

Pins 20 and 24 are right/left audio.

If FL3 is broken the analog portions (such as op-amps, I don't know if DAC needs it, haven't checked) don't get negative supply voltage so both audio channels could be silent.

If the filters are are big as in the pictures I have seen then it can easily break if it gets a some kind of bump or shock when you handle the card.

For testing purposes I would just use a wire to bypass FL3 and see if the card works, if it does then just replace it.

Also here is a juicy 8MP photo of the SCB-55 without any L/R patches 😀 (click on it to eventually get the full-res version)

keropi wrote:

(click on it to eventually get the full-res version)

W00t? No fullsize embedding that some people love to do?

I don't have anything to add to the discussion, at this point. I replaced FL3 on an SCB-55 a few years back, which is the -12V line, as Jepael mentioned. Bridging the connection has been discussed before as well, for cases where the filter is entirely missing. It sounds like you may just have a broken or cracked solder joint?

These surface-mounted line filters are obviously a weak point of the the SCB-55 design. I would suggest not breathing on them, or giving them sideways glances, lest they simply fall right off.

I have removed the damaged filter. The only substitute i can order is this one : http://export.farnell.com/tdk/acf451832-103-t … t=ACF451832-103

Which does not look like the original 🙁
Bit what can you do. I am thinking of replacing all of them, but that is quite pointless.

^ did you try with a temporary connection? does the card work again?

I didn't. I couldn't find my LAN cable wires i have somewhere 😒
I will try tomorrow. I should connect the first and third pin (not the middle)?

Stojke wrote:

I didn't. I couldn't find my LAN cable wires i have somewhere 😒
I will try tomorrow. I should connect the first and third pin (not the middle)?

Yes, only connect the outer pads. the middle one is ground.

Here is the patch work : SCB-55 Jumpered
Sound is back, and better than ever 😀
Seems that the contact was loose when i tried it first, because now the sound is much better.

Does the filter have any major impact? I ordered two (just in case) to replace it, but to me it seems that there is no need?

great!
the filter is there for a reason: to prevent electrical noise getting in the card... it's not essential but this is a sound device and having less noise is always better. I would replace it anyways

Replaced the filter with a new one, works like new 😀
Was a little trouble getting it to balance on the middle of all 3 pads, but in the end i got it.

Hi all, i know this is very old topic but it fits my case and i'd like to know if Stojke that has solved his problem is still online 😀 , i cannot see the snap of his patch work cause it's too old ....
So i need some help, scb-55 is like new but no sound , first af all, just to start: should i measure the filters while still on board or should take them out ?
and does it cause problem if i shortcut on the board to bypass the filter ?
Thanks a lot 😀