What is this item found on a PCB? - Page 1
Forum section: electronics / beginners

author: upl8
author_rank: Contributor
timestamp: April 14, 2019, 07:36:09 am
content: Found this attached to the PCB of a Tivo. It has small holes in the middle of the case and loose balls inside. It was face-down with only the white paper backing showing from above. The only identifier on it is W09.

author: Psi
author_rank: Super Contributor
timestamp: April 14, 2019, 08:04:38 am
content: My guess is moisture absorber/ desiccate.

author: rstofer
author_rank: Super Contributor
timestamp: April 14, 2019, 08:21:13 am
content: Maybe it provides weight.

author: ataradov
author_rank: Super Contributor
timestamp: April 14, 2019, 08:23:11 am
content: Weight was my first guess, but TiVO is a set top box like thing. I doubt it needs any additional weight.But if this was on the remote, for example, then it is probably a dummy weight to make it feel more balanced.

author: upl8
author_rank: Contributor
timestamp: April 14, 2019, 08:35:30 am
content: It only weighs 1.5 grams. As ataradov said, the Tivo is like a set top box. It has a 3.5" hard disk in it, so no need for an extra 1.5 grams. The balls inside aren't attracted to a magnet, but they easily pick up a static charge.

author: sleemanj
author_rank: Super Contributor
timestamp: April 14, 2019, 10:25:35 am
content: My guess is a spill detector, maybe changes colour or something when the balls get wet.

author: Psi
author_rank: Super Contributor
timestamp: April 14, 2019, 10:27:35 am
content: can we see more photos front different angles and also see a shot of it on the pcb?

author: upl8
author_rank: Contributor
timestamp: April 14, 2019, 11:24:02 am
content: Quote from: sleemanj on April 14, 2019, 10:25:35 amI poured some water over it. The face that was visible when it was attached shows some black now, but I'm not sure it's permanent.Quote from: Psi on April 14, 2019, 10:27:35 amSome more photos attached. Unfortunately the PCB is gone. My Dad pulled it apart and asked me if I knew what it was. The "Top" photo is what you would see when looking at the PCB. The holes were facing down towards the PCB. The "Size" photo shows the residue from the glue that was holding it to the board. The five small holes are in the circle in the middle.

author: Psi
author_rank: Super Contributor
timestamp: April 14, 2019, 12:09:14 pm
content: It also reminds me of insect bait/poison.

author: upl8
author_rank: Contributor
timestamp: April 15, 2019, 10:56:57 am
content: The top turned white again after it dried, so not a spill detector.

author: iMo
author_rank: Super Contributor
timestamp: April 15, 2019, 11:34:40 am
content: Looks like activated charcoal (carbon) in form of balls.Absorbs smell of B and C movies

author: CJay
author_rank: Super Contributor
timestamp: April 15, 2019, 12:30:26 pm
content: Ah, all these educated people and none have realised it's an implementation of the CD-ROM CAV disc balancing system referenced in the patent link below for PCB balancing to ensure level flight and accurate aim in repair shops in the even of the board being designatedFailedUnderContinuousTesthttps://patents.google.com/patent/US6061325A/en

author: mikeselectricstuff
author_rank: Super Contributor
timestamp: April 15, 2019, 12:38:30 pm
content: Seems to have some PCB-trace like patterns on the surface - were there PCB tracks under it?If so it could maybe some kind of humidity or maybe motion /shock sensor. Are the balls conductive?

author: Bud
author_rank: Super Contributor
timestamp: April 15, 2019, 01:26:56 pm
content: Why would a goddamn tv streaming box would need a humidity or motion sensor.

author: mikeselectricstuff
author_rank: Super Contributor
timestamp: April 15, 2019, 01:39:49 pm
content: Quote from: Bud on April 15, 2019, 01:26:56 pmHard disk warranty claims

author: Psi
author_rank: Super Contributor
timestamp: April 15, 2019, 01:44:58 pm
content: It couples to 3 capacitive touch pads on the pcb and provides a random number seed.Effected by the position/stackup of those black spheres as well as humidity.

author: mikeselectricstuff
author_rank: Super Contributor
timestamp: April 15, 2019, 02:08:17 pm
content: Quote from: Psi on April 15, 2019, 01:44:58 pmWhy would they not use timing of user remote buttons and/or network activity for random seeding ?

author: Psi
author_rank: Super Contributor
timestamp: April 15, 2019, 11:07:36 pm
content: Quote from: mikeselectricstuff on April 15, 2019, 02:08:17 pmdunno, i'm just trying to think up as many ideas as i can.

author: Brumby
author_rank: Unknown
timestamp: April 15, 2019, 11:13:45 pm
content: Quote from: mikeselectricstuff on April 15, 2019, 01:39:49 pm... or spilled beer detector?

author: Psi
author_rank: Super Contributor
timestamp: April 16, 2019, 12:05:11 am
content: It looks the same as this thing from inside a HDD, just a different plastic packagehttps://youtu.be/5pP2tcsCnrk?t=85I stand by my first guess

author: xavier60
author_rank: Super Contributor
timestamp: April 16, 2019, 02:37:36 am
content: spherical activated carbon beads from this manufacturer can be 0.7mm average diameter,http://www.kureha.com/pdfs/Kureha-BAC-Bead-Activated-Carbon.pdf

author: windsmurf
author_rank: Frequent Contributor
timestamp: April 16, 2019, 03:34:10 am
content: So that must have come out of the hard drive in the Tivo?

author: upl8
author_rank: Contributor
timestamp: April 16, 2019, 10:10:42 am
content: Quote from: mikeselectricstuff on April 15, 2019, 12:38:30 pmHe doesn't remember seeing any tracks under it. I don't think the balls are conductive, they stick to the side of the case if you shake it (static).Quote from: Psi on April 16, 2019, 12:05:11 amYes, I think your are right. Even the texture of the balls looks the same under magnification.Quote from: xavier60 on April 16, 2019, 02:37:36 amSize looks about right.Quote from: windsmurf on April 16, 2019, 03:34:10 amI asked him today. Not from inside the drive, but it was attached to the PCB on the drive. I didn't know this until today.So it looks like this might be a desiccant and/or filter attached by the HDD manufacturer. Found an image that looks very similar.Thanks all for your suggestions, I think the mystery is solved.

author: mikeselectricstuff
author_rank: Super Contributor
timestamp: April 16, 2019, 11:25:15 am
content: Quote from: upl8 on April 16, 2019, 10:10:42 amthey would stick regardless of conductivity

author: upl8
author_rank: Contributor
timestamp: April 16, 2019, 03:27:05 pm
content: Quote from: mikeselectricstuff on April 16, 2019, 11:25:15 amIs that because the balls are contained in an insulating case?

author: Ranayna
author_rank: Super Contributor
timestamp: April 16, 2019, 08:31:31 pm
content: An air filter was what came to mind first, seeing those pictures. With the added information that this came directly from the harddrive and not somewhere else in the recorder, that is confirmed in my opinionYou may be aware or not (a surpising amount of people are not), that most harddrives cannot be airtight and no harddrive has a vacuum inside. The heads need a cushion of air to float over the surface of the disk. Having the internal and external presure equalized is important for most harddisk. On almost every harddisk (except of course Helium filled ones) you will find a breather hole somewhere. This is the first time i see an external filter though. I'm sure there is also an internal filter, otherwise just removing the PCB might break the disk.Do you know the model of disk? Now i'm curious

author: upl8
author_rank: Contributor
timestamp: April 17, 2019, 09:35:06 am
content: Thanks. Yes, I was aware that the heads float on a cushion of air. Amazing devices.The drive is (or was) a WD3200AVVS-63L2B0. I can't find any photos showing the filter.

author: Ranayna
author_rank: Super Contributor
timestamp: April 17, 2019, 11:27:13 am
content: If I remember correctly, it has been a long time since I tore down a WD harddisk, for that style of case the filter is stuck on the inside of the lid, just where the clearly visible breather hole is. I was not able to find a picture of the lid though.It certainly was not attached to the interface PCB of the harddisk. Maybe there was some kind of extra attached filter, but that would not be something that is fitted by Western Digital.

author: Ranayna
author_rank: Super Contributor
timestamp: April 23, 2019, 10:43:15 am
content: Somehow that topic nagged meSo, at work I found a similar 250 GB Western Digital Harddrive in the junkbin. The lid is the same as yours (or at least looks the same)One removed label and 7 screws later I had the confirmation: That little clear plastic box filled with small black spheres is stuck on the inside of the lid beneath the two (one is covered by the label) breather holes. I cannot provide photos at the moment, but the filter looks exactly like the one you posted.