Mechanical rattle from SB3

[verbatone]

Hi, I figured this forum section would be the best place to post this...When certain bass notes are hit, I get a nasty rattle from the SB3. I hooked up my function generator to the amp and it's right around 75Hz which is the worst. I can generally fix the problem by sticking a thick piece of paper between the plastic case and the plastic screen for the display near the top left edge. That tends to make the bulk of the vibration rattles go away.

It's not too bad when your across the room from it, but when you are next to the SB3, it's rather irritating.

Anyone have an idea for a fix? I haven't opened up the SB3 yet, and I'm wondering if there's any good internal solutions for this.

I've went to some lengths to exterminate rattles in my old 60's console that it's on, and this is pretty much the last rattle to get rid of.

[seanadams]

It's easy to open if you have the right tools - you need a torx t-10 screwdriver. The most likely culprits I could think of would be the 3300uf cap or the cables that go to the two antennas. I have never heard of this being a problem before - I could check here with a microphone, but if it's a cable routing or part placement issue then it probably would not show up the same way on a different unit.

[verbatone]

Thanks Sean,

Hmmm, really seems like a plastic rattle. We have a set of torx drivers in the lab at work (I'm an electro-acoustics/audio engineer), but I wanted to check here before opening the unit. I'll check it out. If it's a cap or cable, I'll let you know. I'll try snugging the screws up and see if that helps first.

If another unit has the same problems as mine, you wouldn't need a microphone to observe it, the harmonics of the vibration are very audible and correlated with the bass envelope. Initially I thought it was the preamp my SB3 is sitting on cause it was so loud, but it turns out when I lift the SB3, mechanically isolating it, my whole setup no longer rattles.

Pin pointing the rattle took a bit, but once I held the upper left corner of the display tightly, the rattle ends. So the piece of paper just forces distance and pressure between the display face and the plastic housing, which seems to limit the rattle. Unfortunately this looks bad, so I'm trying to figure out if there's an internal solution.

My bezel is coming off too, which I'm going to fix with double sided 3M tape, so that probably gives you an idea of the era my device was manufactured.

[seanadams]

In any case it sounds like you may want to contact support and request a replacement front panel. The adhesion problem was fixed a long time ago. I suppose the case may not be torqued down properly, but that seems less likely to me to cause a rattle. The screwdrivers we use are calibrated, but maybe there was some deformation of the plastic bosses or something.

[verbatone]

Doh, brought home a t10 torx and it doesn't fit the screw heads. I'm I missing something? Doesn't much matter, I'll take the SB3 to work and we have the full array of torx drivers.

Looking at the unit up close (and in person), the upper left of the display screen can actually be pulled away from the plastic housing by about 1mm rather easily. The upper right side can't though. Seems like something isn't right. Maybe when I get to the inside I'll see something.

What's the torque on the drivers? 6,8N? We also have calibrated torque drivers in the lab.

[seanadams]

I don't know what we calibrate them to - reasonably hand tight is all it needs. I'm quite sure they're T-10 though.

[verbatone]

Sean, so you were half right, the internal torx are t10, but, at least on my unit, the outer screws are t8. But that doesn't really matter (so why do I point it out you ask!!)

Anyway, I took the screen off played a particularly bad song and most of the buzz went away.

So I took the SB3 completely apart and saw there were two leaded electrolytic capacitors in the back. One of them was the 3000uF you mentioned and another was a smaller near the daughter board which routes power/spdif/audio/etc. That one was touching the daughter card. So I moved it away and sorta mucked with the wifi cables. Anyway, something made a difference internally cause without the faceplate, the unit is dead quite.

I put the faceplate back on and it buzzed again. So I took it off and looked widthwise across the top and there's a slight co-planarity issue. So I stacked up some thick tape around the top left corner of the screen where it fits inside the plastic housing. Now it's quiet and the tape can't be seen!

Thanks again for the help! Best forum ever!

[seanadams]

Interesting. I will have a closer look and see if any change to the design or the assembly procedure is in order.

BTW, the thing the microphone is good for is not so much to confirm that it's making a noise, but to pinpoint the source.

[verbatone]

Agreed, a good uni-mic would get the job done. I'd be interested in any results you find, although I can see how this might be low on the list of priorities. Take care.