[SOLVED] DC Jack Cable Too Short

[omnichad]

This replacement laptop DC jack cable is too short by about an inch. Does anyone know what the loop in the middle of the cable does? I'm sure it could be EM noise reduction or something along those lines.

If I cut that plastic brick out of the middle to get rid of the loop, it might fit. What would you do? Looks like the customer will be without their laptop for several more days waiting on eBay otherwise.

 

[Slaters Kustum Machines]

You could extend the new one with part of the old one if you are good at soldering. With shrink wrap you wouldn't even know it happened.

 

[jbartlett323]

Its a ferrite core, and it is indeed there to lower interference from the power line. Removing it can have... unexpected... consequences. But may not see any difference at all. I wouldn't remove it personally, I would either extend it as said above, or get another.

 

[omnichad]

if you are good at soldering.

Not at all. I have desoldered and replaced dc jacks directly on the motherboard, but it is not a pleasant experience. Combining two wires would be like magic to me.

 

[Slaters Kustum Machines]

In that case, get a different cable. I'd offer to extend it for shipping charges, but by then you could have a new cable.

 

[omnichad]

Its a ferrite core.

That was definitely my first thought, but it looks so much like plastic that I wasn't sure.

Either way, the ferrite core doesn't fit in the slot of the original, so it looks like I'm off to eBay. If I could unwind the cable and put it around the smaller ferrite core on the original, I might have enough length. But they glued the wires into the motherboard side of the connector, so they aren't coming back out.

 

[omnichad]

In that case, get a different cable. I'd offer to extend it for shipping charges, but by then you could have a new cable.

I found one on eBay that looks exactly like the OEM cable. With Priority Mail I might have it Saturday. I was trying to expedite it, so I ordered the part before I got home and got the laptop open. That might be the last time I do that.

 

[Porthos]

I was trying to expedite it, so I ordered the part before I got home and got the laptop open. That might be the last time I do that.

Yup.

 

[Matthew Bradley]

Why not just repair the old one? Looks like you have some disconnected wires from the DC jack end.

 

[omnichad]

Why not just repair the old one? Looks like you have some disconnected wires from the DC jack end.

Broken wires, actually. Plastic inside the connector is cracked too. Part is not expensive enough that I would ever risk re-using the original on one of these repairs.

 

[Markverhyden]

Broken wires, actually. Plastic inside the connector is cracked too. Part is not expensive enough that I would ever risk re-using the original on one of these repairs.

Out of curiosity did you order the part based on the OEM part number?

 

[Moltuae]

That was definitely my first thought, but it looks so much like plastic that I wasn't sure.

They're often housed in a plastic case.

We tend to refer to them as ferrite beads in electronics. The purpose is usually to prevent the cable acting as an antenna, either as a receiver of interference or as a transmitter of interference. In power cables it's usually the latter effect we're trying to suppress, especially when working with switched-mode power supplies, which can generate a lot of high frequency harmonics.

Often you can remove ferrite beads and there will be no apparent issues, especially if the original cable had none. However, if you're replacing an internal cable with a ferrite bead you should always ensure the replacement cable has a similar ferrite bead, not only to prevent operational issues but also to keep the equipment electromagnetically compliant. In many cases, interference suppression devices such as ferrite beads are there to help equipment conform with mandatory regulations such as CE and FCC compliance. Removing a single bead, in some cases, could possibly render a device non-compliant.

Watch the first few minutes of this video if you want to see how effective a simple ferrite bead is at filtering high frequency interference:

 

[omnichad]

Out of curiosity did you order the part based on the OEM part number?

The listing I ordered from had the correct OEM part number, but I ordered based on the laptop model number. What I received was way out of spec with the OEM part shape and length.

And that's only because I hadn't disassembled the laptop yet - I had only an hour to hit the one-day shipping deadline and I was 30 minutes away from my bench.