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Fuse for webcam + fingerprint reader?

Posted: Sat Mar 25, 2017 5:27 pm
by ricard
While replacing the screen on my T400, I accidentally got the metal wire connecting the two lid latches on the wrong side of the plastic film emanating from the webcam, which caused it to stop working. Even after putting the wire back behind the film, the webcam won't work, it doesn't show up in lsusb - and incidentally neither does the fingerprint reader which I assume is also an USB device.

In fact my lsusb is rather sparse:

Bus 002 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
Bus 008 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub
Bus 007 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub
Bus 006 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub
Bus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
Bus 005 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub
Bus 004 Device 002: ID 0a5c:2145 Broadcom Corp. BCM2045B (BDC-2.1) [Bluetooth Controller]
Bus 004 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub
Bus 003 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub

My guess is that I've shorted the USB bus supplying the camera and the fingerprint reader. Does anyone have a clue as to where the corresponding fuse might be located on the motherboard? Or if I've made the right diagnosis to start with? An lsusb from a similarily spec'd machine would be helpful (the type number is 2768-CTO, the screen is 1280x800 and it has as mentioned both a fingerprint reader and a webcam).

Incidentally, I've tried replacing the webcam but it didn't make any different.

Re: Fuse for webcam + fingerprint reader?

Posted: Sun Apr 02, 2017 5:52 pm
by 4uk4a
You need to check the fuse F16 - it is responsible for the camera.
See: http://forum.thinkpads.com/viewtopic.ph ... 81#p756353

Perhaps the scheme will help, p.29

http://docslide.us/documents/lenovo-t40 ... v-142.html

Re: Fuse for webcam + fingerprint reader?

Posted: Sun Apr 02, 2017 11:46 pm
by ricard
Thanks. The real problem now was finding F16, but eventually I found a reference to a T61 on another forum (can't remember which one now), which also mentioned where the fuse was located - near the LCD connector on the underside of the motherboard. Turns out it is in a similar location in the T400, so located the fuse, and yes, it is open circuit.

I could jumper it I suppose but I think I'll replace with a new one it to avoid further issues if a short appears again.

Thanks for the schematics. How do these things actually surface? It appears even Lenovo doesn't repair motherboards, only replace them if something goes wrong. So the motivation for them to supply schematics to anyone would seem rather small.

BTW, I found this reference to how to get at the bottom of the motherboard without having to remove everything on top of the board:

https://superuser.com/questions/992222/ ... vo-t400-la

I would add that there is a cable from the USB connector on the right hand side of the machine that needs to be detached too. I couldn't actually get the internal connector through the appropriate whole in the chassis to completely remove the bottom case, but it doesn't really matter as it's possible to get at the bottom of the motherboard anyway by just pulling as much of the cable (10 cm or so) through as possible.

Re: Fuse for webcam + fingerprint reader?

Posted: Mon Apr 03, 2017 2:45 pm
by 4uk4a
Hi,
Perhaps you will be interested in doing a comparison(click on the picture):
http://thinkwiki.de/T61_Sicherungen

I think that you are looking for this:
https://goo.gl/rDzjwb

For soldering it is better to use this or something like this:
http://landelet.it/shop/img/p/3/3/9/339 ... efault.jpg

Schemes can be bought (5-10 euros), but I'm looking for Russian sites, for example for T400:
http://remont-aud.net/pda/load/noutbuki/306-143-3

Re: Fuse for webcam + fingerprint reader?

Posted: Mon Apr 03, 2017 3:48 pm
by rkawakami
Getting a little off topic...
ricard wrote:Thanks for the schematics. How do these things actually surface? It appears even Lenovo doesn't repair motherboards, only replace them if something goes wrong. So the motivation for them to supply schematics to anyone would seem rather small.
There are several online sellers of laptop schematics that you can find easily enough, given a logically-structured Google query. You can even find people giving them away if you look harder (being able to read Chinese or Russian helps; or simply use Google Translate). I would say that all of them are violating / ignoring the legal warnings embedded in the documents that state that they are "proprietary" and/or "confidential". My guess is that they were liberated from their associated factories (IBM, Lenovo, Acer, LG, Wistron, ASUS, Quanta; did I miss anybody?) by employees looking to increase their income or maybe they simply gave them away in an attempt to be helpful to us tinkerers out here.

Schematics by themselves are fairly good references, however what makes even more useful is if you can find an associated board view file. This file is a graphical representation of the components that are on the motherboard. It allows for searching by a particular part number and will show how it is interconnected to the other parts on the board. There are a couple of mutually-exclusive file formats (and related programs that you must use) that can provide this information.

Re: Fuse for webcam + fingerprint reader?

Posted: Mon Apr 03, 2017 4:58 pm
by ricard
Thanks guys, great tips there.

Re: Fuse for webcam + fingerprint reader?

Posted: Thu Apr 13, 2017 5:01 pm
by ricard
Ok, so just a follow-up to complete this thread. Instead of buying a fuse off eBay, I opted for a more local electronics reseller, partly because of shorter delivery times and partly because I didn't want to take any risks with a fuse, feeling more comfortable with a component from Schurter than some far east noname brand.

The package for the SMD fuse incidentally is an 0603.

Replaced the fuse by first cleaning off the old solder using desoldering braid, then put a minute amount of solder on one pad, carefully placed the fuse, reheated the pad with the solder, then soldered the other pad. Powered up, and the camera now showed up in the BIOS which it didn't previously. Mounted everything back together, started Linux, ran cheese and the webcam came up nicely. Queue sigh of relief ... apparently my fingerprint reader still doesn't show up in lsusb, but I've never used it so it may never have worked ... not worrying about that now anyway.

Thanks again for all help!

(I really like my old T400 by the way. The fan is super quiet and my HGST 500 GB 5400 RPM hard drive is too. The 16:10 format gives me a good font size compared to the more modern 14" 16:9 screens. Pity the T400 was the last one Lenovo made in that format).