Hello

My first post here.
I have a Philips Soundbar FB1 with no power. After disassembling I checked the power source, which is ok and delivering 24v to the mainboard.
On the mainboard itself (Richsound, B918) I found at least one damaged component (marked).

Some sort of a step down converter. Labeled: LA3484A.
Closer look through the microscope:


I already ordered a simmilar one EUP3484A and desoldered the damaged chip, because I had a lot of continuity readings with the multimeter on several Caps, directly after that Chip and around the bigger Chip below (first image, "ITE"), which is some kind of HDMI controller I guess.
I still have the continuity readings with the multimeter and wondering if this could be normal or maybe a short somewhere else.
I'm not pro so there is a lot of guessing.

What would you do now? Just replace the burned converter and try it or is there definetely somewhere else a short when some Caps on the board are ok and some in a specific area seems short?

Unfortunaltey I have no power supply to inject voltage, neither a thermal camera to find heatspots.

best regards
Lennart

 

Hi,
If you have the datasheet for the i.c. Before fitting the new i.c. Check the pads to see if there are any shorts to ground ( 0V ) with your ohm meter.
Good luck..........

 

You cannot measure capacitors in-circuit without knowing what else is connected to them. For a proper test, the capacitors need to be removed from the circuit board.

 

Hello Lennart,
Did you manage to fix your FB1 in the end?
On my board, U1 outputs 5 V and the output capacitors show no short circuit on the ohm meter. I suspect your FB1 may have had a component short that caused U1 to burn out.
My FB1 has a similar issue — I noticed the 3.3 V rail rising to about 3.58 V, but I still can’t identify which regulator is responsible for it. I’d appreciate it if anyone can help locate it.
Best regards,
Eric