8800NL - high pitched noise

[gatekeeper]

Charlie,

Well done!

I've had no incentive to undertake the kind of remedial action you've taken because I don't operate my 8800NL in VDSL mode as yet and don't have the noise problem to which jrawle originally alluded. But had I been enduring the noise I'd have eventually done exactly what you've done.

An additional thing I'd have done would have been to apply a dab of suitable hard-setting adhesive to the base of L18 eg. 2-part Araldite, once its quietest position was found, to more firmly couple it mechanically to the circuitboard. Most adhesives are electrically non-conductive. If coupling it more firmly to the board were to worsen the noise, however - which is always possible - then maybe stuffing a small, thin, resilient piece of non-conducting material, eg. foam rubber, into the base of the choke would do the trick. The idea would be to dampen and dissipate the HF resonance.

Did you check to see whether any other chokes/inductors were similarly precariously mounted? For example, I've noticed that, in the photo, L4 is about an inch away from L18.

[analogue]

A little blob of glue from a hot glue gun on the offending choke will complete the repair.

[WaypointCharlie]

With high frequency signals flying about I didn't want to risk doing anything more than necessary to get rid of the horrible noise, although that part of the circuit does look like a relatively low frequency power inverter.

The other chokes are mounted closer to the board. Perhaps L18 is supposed to be fitted closer, or there may be a reason for leaving the legs long (e.g. cooling), but it does leave them prone to 'singing'. Anyway, it seems to be fixed.

8800NL_fix2.jpg

[gatekeeper]

From the picture it looks like it's already closely coupled to the board. Also, we can now see that the choke uses a fairly broad gauge of copper wire but in a very small diameter. This must be putting the coil under more mechanical tension than normal, causing adjacent turns to momentarily touch when the coil's in use (when a varying current's passing through it), producing the 'zinging' noise. It seems that your adjustment relieved that tension, or separated the turns, sufficient to stop the 'zinging'.

If all the zinging L18s are like this, ie. are already close to the board, then some minute repositioning of the choke, plus a blob of glue as suggested by analogue, is all that's needed.

Doubtless, there'll be some affected users who'll not want to take this DIY route for fear of invalidating the warranty, but at least they'll now know that it's fixable.

Anyway, once again Charlie, many thanks for pursuing the matter, finding the solution, and then informing us.

[jrawle]

I just happened to look back at the forum today and saw these posts. It's great that you have identified the problem and managed to fix it. It also proves it is an internal component of the router that produces the noise, and not the power supply, or some sort of external interference in people's particular setups.

My router isn't bothering me in its current location. If in the future I want to locate it elsewhere, meaning I can hear it again, I'll certainly give the fix a go. Thanks for posting!