Chinese Bose speaker, PCB tracing - Page 1
Forum section: electronics / repair

author: superpatosainz
author_rank: Contributor
timestamp: March 08, 2016, 02:27:44 am
content: Hello world!I've been trying to do the world's most classic repair (right after the leaked cap): a broken microUSB port.I have a Chinese Bose soundlink (portable speaker) replica, and surprisingly(?) its microUSB port came loose.It's been sheared apart by somebody else who tried to repair this, and the PCB scratched as a side effect: Thing is, I don't have enough experience to trace this PCB effectively (it's practically single-sided, the other side just has a couple of traces that I think have nothing to do with the charching circuit). My intention is to solder-hack two USB power wires into wherever the microUSB ports dumped energy: but I cannot just find where to tap into the PCB to supply 5V. Can I please get some help from you pros?Top right connector goes to a 3.7V LiPo cell, bottom right is where the microUSB port used to be.Thanks!

author: MyHeadHz
author_rank: Regular Contributor
timestamp: March 08, 2016, 07:13:24 am
content: Is it supposed ti be where the grey area is in the bottom-right? It is ahrd to tell from the picture, but it looks like some serious damage to a few traces.If that's correct, you would probably be better off just soldering on another microUSB port, wired directly from the ends of the traces (at the nearest component- skipping the partial traces). There seems to be enough of the traces gone that you might have trouble reverse-engineering that bit to figure out which wire goes where. do you have a picture of a good board as a reference?

author: superpatosainz
author_rank: Contributor
timestamp: March 08, 2016, 09:45:30 am
content: Quote from: MyHeadHz on March 08, 2016, 07:13:24 amYes, bottom right. The guy who tried to to this before me had dremel'd the area where the microUSB port lied (the madman!).Unluckily, I have no picture of the "good board" and there's no service manual since this is a chinese product, not the original. This is where the biggest difficulty with this repair lies.As a clue, the LED to the left of where the port used to be lighted up when it was charging.

author: Philfreeze
author_rank: Regular Contributor
timestamp: March 08, 2016, 10:27:05 am
content: Cou you make a top down picture of the bottom right of the board?It would be helpful to actually see the traces without obstructions.And do you know if this device was able to transmitt something via USB?If not then the LED just left to the now gone USB port is probably connected between GND and VCC (over an R) right?

author: superpatosainz
author_rank: Contributor
timestamp: March 08, 2016, 09:34:04 pm
content: Quote from: Philfreeze on March 08, 2016, 10:27:05 amHere are a couple better pics, including bottom side:microUSB was used for power only.

author: Aodhan145
author_rank: Frequent Contributor
timestamp: March 08, 2016, 11:47:54 pm
content: Quote from: superpatosainz on March 08, 2016, 09:34:04 pmYou may be in luck then. Try finding a know 5V and ground point and try applying power but if there are other traces damaged this could be a bad idea..

author: superpatosainz
author_rank: Contributor
timestamp: March 09, 2016, 01:33:54 am
content: Quote from: Aodhan145 on March 08, 2016, 11:47:54 pmWell here's my problem: I can't find where the microUSB dumped power to, so I cannot apply power to points that are unknown to me, hence this thread and my cry for help at tracing this.

author: desy2820
author_rank: Contributor
timestamp: March 09, 2016, 02:46:46 am
content: I'd suggest finding datasheets for the various ICs, especially the ones for the LiPo charging system. You want to identify the power and ground pins, then try tracing them on the PCB. Hopefully this will lead you somewhere near the USB connector.I hope this helps.

author: sleemanj
author_rank: Super Contributor
timestamp: March 09, 2016, 03:35:09 am
content: Last picture, 5 pin connector on the bottom, what are the silkscreen markings. Looks like GND and PWR there to me.

author: superpatosainz
author_rank: Contributor
timestamp: March 09, 2016, 09:39:25 am
content: Quote from: sleemanj on March 09, 2016, 03:35:09 amThere's also a 3V3 rail there, but, I don't see why it'd make sense to supply the charging 5V to just some buttons on a front panel (that's where the connecter goes to).

author: Aodhan145
author_rank: Frequent Contributor
timestamp: March 09, 2016, 07:09:20 pm
content: It must generate the 3.3v rail from the usb so the 5v rail should be the only one you need to power.

author: superpatosainz
author_rank: Contributor
timestamp: March 09, 2016, 08:50:54 pm
content: Quote from: Aodhan145 on March 09, 2016, 07:09:20 pmThing is: where is this 5V rail? It sure isn't the PWR pin (I checked with my multimeter) (nor any other pin there).My understanding is that there's a charging circuit that charges the LiPO cell which later goes to a voltage regulator that provides stable 3V3. I need to tap into this charging circuit.

author: sleemanj
author_rank: Super Contributor
timestamp: March 09, 2016, 10:10:29 pm
content: What is the large 4 pin connector on the back side of the board that sort of looks like a USB-A Female?

author: superpatosainz
author_rank: Contributor
timestamp: March 09, 2016, 10:43:17 pm
content: Quote from: sleemanj on March 09, 2016, 10:10:29 pmIt's exactly that. But it's for reading data from a flash drive. The former microUSB port was used for charging.

author: Philfreeze
author_rank: Regular Contributor
timestamp: March 11, 2016, 10:02:33 am
content: Link to picture because I am too lazy to upload ithttps://www.dropbox.com/s/tht2ln9lmm2rwxk/repair.png?dl=0Does this make sense?

author: superpatosainz
author_rank: Contributor
timestamp: March 11, 2016, 10:21:35 pm
content: Quote from: Philfreeze on March 11, 2016, 10:02:33 amI do understand what you wrote.That resistor you thought was 0 Ohm is actually 8 Ohm, may be lower but probably that's because of my probe placing.So should I tap into your orange circles for +5V? And what about ground? Do you think both USBs share the same GND?

author: Clear as mud
author_rank: Regular Contributor
timestamp: March 13, 2016, 12:11:29 am
content: It looks like most things on that board share the same ground. The largest fill areas on both top and bottom are ground planes, and most of the vias in them are there to stitch together the top and bottom ground plane. You can see one side of the LED is hooked to the ground plane, one side of the large capacitor BC1 on the top side of the board, the marked GND pin on the five-pin connector, the ground pin and the shield on the existing USB connector, as well as other things are all connected to that same ground plane.You said the USB B port is for a flash drive, so it is intended only to provide power to the flash drive, not to accept power input there. Depending on how they did the power switching, the device might still work and charge if you apply 5V power there, but it would be better to fix it with a new micro-USB port like you were planning. I think that both transistors, at top right (Q3) and at top left (Q1) are for power switching and/or anti-backfeed functions.My best guess is that the micro-USB port had its ground connected directly to the common ground plane, and its +5volt pin connected directly to the anode of the large diode at top-right, D1.

author: Philfreeze
author_rank: Regular Contributor
timestamp: March 14, 2016, 10:48:22 am
content: Quote from: Clear as mud on March 13, 2016, 12:11:29 amI think Clear as mud is right (mainly because it perfectly coexists with the tracing I did).the anode (right side) of D1 is connected with one pin of Q3 (top-right one) and then also with the open pad of R23 (top one). The bottom-right pin of Q3 is then connected to my orange line wich has a thicker trace and all that.To fix it I would probably use the free pad of R23 (probe it to see if it is really connected to the diode first) and the upper pad of R8 which is connected to GND.

author: senso
author_rank: Frequent Contributor
timestamp: March 14, 2016, 02:58:18 pm
content: I would say that it would connect the +5v to the right of the diode, and gnd is anywhere you like it.It was mounted in those "half" holes, thats why it sheared, usual chinese design to save 1mm of pcb.

author: superpatosainz
author_rank: Contributor
timestamp: March 14, 2016, 11:28:19 pm
content: Quote from: Clear as mud on March 13, 2016, 12:11:29 amWorked like a charm! Thanks! (In hindsight it seemed very obvious... oh well, it's 20/20)(Kudos to everyone else who chimed in! Really appreciated it)

author: superpatosainz
author_rank: Contributor
timestamp: March 14, 2016, 11:30:24 pm
content: Quote from: senso on March 14, 2016, 02:58:18 pmGotta love those markets of scale.