Please help me identify this component (BD1)

[RocknRoll]

Hi

Last night, I connected my Creative SoundBlaster Jam BT headset to charge and I heard a pop sound accompanied with the smell of a burnt component. I opened up the headphone to find the circuit shown in the attachement. It seems to be a protection circuit but I have no idea. Would you be able to help me find out what this component is so that I can repalce it ? It seems to have been labeled as BD1 which is next to another component that is ESD1.

I am assuming both ESD1 and BD1 are diodes. However, when I used the diode test function on my multimeter and ESD1 showed nothing. It did show a stable 200kOhm resistance though.

Any help would be appreciated.

Best
Jai

[fzabkar]

You should check the other side of the PCB for damaged components. Also confirm that your charger is outputting the correct voltage.

[RocknRoll]

Sorry, I realized that I was not being clear. BD1 had completely burned hence there is nothing there (I wiped it with a tiny bit of IPA). There is nothing unusual on the back the of the circuit. It appears that BD1 is the only element that completely burned.

Best wishes
Jai

[fzabkar]

Here are internal photos from the FCC web site:

https://fccid.io/IBAAVPGH0300/Internal-Photos/Internal-Photos-2479160

The damaged component does not appear to have a stripe, so it may not be a diode.

There appears to be another BD0 (or BD8?) part connected to VBAT- (near switch S1 on the other side). Try measuring that.

There is also a BD2 (or 6D2?) near J1.

I suspect that BDn are EMI Suppression Ferrite Beads:

https://www.mouser.com/new/wurth-elektronik/wurth-we-cba-ferrite-beads/

There are other ESDn components adjacent to each switch. Measure those.

Here is the datasheet for the main IC:

CSR8635, Cambridge Silicon Radio Limited, Bluecore single-chip Bluetooth ROM audio solution:
https://www.openhacks.com/uploadsproductos/csr8635-datasheet.pdf

[abdulbadii]

Might be diode bridge

 TVS diode for ESD protection might be labeled/abbreviated ESD, it is a kind of Zener diod

[Colt45]

My money is on ferrite bead too.

[pgo]

Hi,
if it is a ferrite bead as suggested (and I agree) then it is unlikely to be the component that actually failed.
Ferrite beads are low resistance in the first place so shorting does not result in excessive dissipation and going open would not self destruct.
Failure is usually an indication of a gross overload elsewhere.
U2 appears discoloured and it may have overheated. Is it a power regulator/charger IC - the markings are unclear.
bye

[RocknRoll]

The markings on the U2 chip are "428RT K609". It is this eeprom: https://www.mouser.co.uk/ProductDetail/STMicroelectronics/M24128-BRDW6TP?qs=%252B9pWl1iD4MX%2FyDoVWB%2FXxA%3D%3D

I also have a burning suspicion that something else caused this but not sure how to go about troubleshooting.

How important is the ferrite bead, can I just short it ?

[samnmax]

The ferrite can be bridged if nothing else is damaged, but it is very unlikely. First you should make sure that the circuit that BD1 was powering is not shorted. Measure resistance between ground (shielding of the micro USB connector, for example) and the remaining pad of BD1, which seems to go to C28. If this rail is shorted, there's no point in bridging BD1.

[RocknRoll]

Today I borrowed my friends thermal camera to have a look at what is going on. I bridged BD1. I plugged the headphones into a usb port for charging and it immediately started heating up like crazy. The infrared camera showed a bright red spot on the eeprom chip outlined above. I think it is the eeprom chip that is gone :/

Now the question is, can I just replace this eeprom to fix everything or there is some firmware that might be stored in this eeprom which would have to be burned into the chip? What is the purpose of this eeprom, is it for remembering paired devices etc (it is only 128k)?

Many thanks for this amazing discussion everyone.

[fzabkar]

The application diagrams on pages 68 and 69 of the datasheet show that the serial flash IC is powered from a 1.8V supply generated by the 1V8 SMPS block within the CSR8635 IC. The supply for this block comes from either VBAT or another internal 3V3 LDO regulator whose source is the USB VBUS.

In short, it appears that the main IC is dead.

[RocknRoll]

Thank you for this. What do you mean by the main IC ? Do you mean the eeprom chip?

[fzabkar]

CSR8635.

[RocknRoll]

Many thanks. Your technical expertise is much appreciated.

[RocknRoll]

I actually have a quick question. Will replacing the main chip recover function or will I need to burn a firmware into the BT chip ?