Samsung Soundbar Q900T Cuts Off if Volume above 30

[Storyteller12]

I have this soundbar and when I turn it on it works until I turn the volume above 30.
Then the display show “PROT” protection and shuts off.

I can turn it right back on and it works until volume hits 30 again.

There is a little static on the surround speakers so I unplugged them but still have same problem. I tried unplugging all speakers also and when volume goes above 30 it shuts off.

I can turn the volume above 30 if nothing is playing but as soon as I play something it shuts off.

It will play fine for hours with volume around 20-25 without any issues.


I will upload pics of the boards later.

I see there a several “UB6470” ic chips under thermal pads with heatsink. But can’t find any data sheet to verify if there good.

Any help is appreciate trying to troubleshoot.

[Th3_uN1Qu3]

Re: Samsung Soundbar Q900T Cuts Off if Volume above 30

I think it's too new for your issue to be thermal - worth investigating the power supply. Is the power supply internal or does it use a power brick?

[Storyteller12]

Re: Samsung Soundbar Q900T Cuts Off if Volume above 30

Hi,
It has a internal power supply. I did probe a little but it had steady 14v standby and 19v on.

I do have another soundbar I believe with the same power supply I can try.

I’ll let you know how it goes.

Thanks

[Storyteller12]

Re: Samsung Soundbar Q900T Cuts Off if Volume above 30

Ok. I swapped power supply from a q90r with exactly power supply and same problem.

The only service manual I found was for a HW-C450 and it mention the power supply like you said and the audio amps for the protection circuit to kick in. Since it’s not the power supply I’m assuming it’s the audio amp chip I mentioned in my first post. But dont know how to test them and there are 8 total. Don’t want to just replace them randomly

[Storyteller12]

Re: Samsung Soundbar Q900T Cuts Off if Volume above 30

I did some more digging around on google and found a service manual on a hw-h750 with a similar amp ic.

I'm not that familiar with audio so hoping someone can assist in troubleshooting with the schematics I found.

Thanks in advance.