Vizio vt420m sound issue

[Cyklopz]

The above TV will work OK for a while, 10-60mins or so. Eventually, it will develop
+ an issue with sound where the sound seems to get broadcast twice kind of like an echo. The issue will slowly build up worse and worse. At these times I also see a slight flickering of the video but otherwise the video seems fine. I see on this refurbished main board there is some brown discoloring on the audio header (and the plastic looks slightly melted). Any ideas on how to troubleshoot this issue? I've checked the power coming from the power supply board and all lines looked right from there.

Image attached.

Thanks.

Cy

[Cyklopz]

Re: Vizio vt420m sound issue

Additional tests, tried different sources/inputs with same issue on all.

Cy

[CapLeaker]

Re: Vizio vt420m sound issue

someone had either changed or resoldered U409. I can't see the numbers on it, but looks like it could be the audio IC. That's where the discoloring came from.

Edit: 402WP = EEprom. So it had a EEprom replacement.

[budm]

Re: Vizio vt420m sound issue

Which one of these is your main board?
http://www.shopjimmy.com/catalogsear...q=Vizio+vt420m

[Cyklopz]

Re: Vizio vt420m sound issue

My model uses this main board type:

http://www.shopjimmy.com/vizio-cbpf9...main-board.htm

CP

[budm]

Re: Vizio vt420m sound issue

So you already replace the main board, right? What was the original problem with the old board? At this point the power supply will not cause echoing sound problem, that will be something in the sound processor section.
U602 is the Class-d amplifiers for driving the speakers.
Pictures provided by SHOPJIMMY.

[Cyklopz]

Re: Vizio vt420m sound issue

The original problem with the set was the picture would start to get some artifacts over time and the system would eventually reboot itself. I sent the board in for swap/repair (it was swapped for a rebuilt board). The video seems OK now but the audio is having issues. I noticed the brown smoke mark on the audio header and was of course curious about it. No caps appear bad on the main board or the power board.

Anything I can try to check with a meter or pics I can take to try to help troubleshoot?

CP

[budm]

Re: Vizio vt420m sound issue

That CN403 is not connected to audio circuit.
Show us the pictures of the whole back side of the TV.
I think the board you got has problems, i hope it is still under warranty.

[tipitup]

Re: Vizio vt420m sound issue

I have always had this same sound problems with my vt420M, mine happens more when I am playing a dvd. About 34 minutes into it it stars with the sound stuff. Now I have no sound but everything else works great. I'll not hijack this tread with that problem, just confirming a similar problem as this guy.

[aaronwt6]

Re: Vizio vt420m sound issue

Is u409 the eeprom chip as stated above. I've always thought U405 was the eeprom on these? It's a 48 pin TSOP chip NAND128W3A2BN6. I know it's what typically has the panel manufacturer sticker on it and can be swapped between boards to change what panel they will work with. I wasn't trying to hijack the thread either but if U409 is the eeprom I'd prefer to change that when I get one in that's stuck on the Vizio logo screen. Several models use this board.