Vizio SV420M has amber light, wont respond to power button or remote

[triplefour]

another day, another broken TV that's got me scratching my head.
i've narrowed it down to the main board. the PSU can be tricked to turn on and the backlights come on and stay on, and the screen is not cracked so it's definitely worth trying to fix.

the symptom is that the mainboard gets 5vstandby and the vizio logo is amber but nothing happens when you push power on the tv or the remote.
the voltage of pson is about 1.5 and does not change at all when power is pressed.
of course we know it needs to receive the 5v from the mainboard to turn on.

oddly, the 12v from the PSU is on as well, but when mainboard is disconnected, it goes away.


i have checked both fuses on the mainboard and they are good and have 12v and 5v on them.

i checked all the voltage regulators and i know im supposed to write them all down here but HONESTLY i double checked them real good and they are all within spec. 1.25+pin1=pin2 on all of them.

ok fine here they are:

U2
L272
G9117
1. 2.05
2. 3.29
3. 5.16

U4
L272
G9117
1. 0
2. 1.24
3. 3.29

U6
L272
G9117
1. 6.86
2. 8.12
3. 12.19

U7
L272
G9117
1. 2.02
2. 3.26
3. 5.14


and the 2 bigger ones

U3
L354
G1804
1. 2.04
2. 3.29
3. 5.13

U5
L354
G1804
1. 2.04
2. 3.29
3. 5.13

did some random poking around and i noticed CE36 has no voltage...is that something to look at?

i read all the threads i could find on this tv but it doesnt look like any of them end in repair to the mainboard, just a replacement.

any help pointing me in the right direction of what to test next would be greatly appreciated.
thanks!

[R_J]

Re: Vizio SV420M has amber light, wont respond to power button or remote

It's a very good chance the eeprom is bad, If you have any freeze spray (inverted can of compressed air) will work, Unplug tv, freeze eeprom ic, plug in tv and try turning on.
The eeprom is usually an 8 pin ic somewhere on the board

[triplefour]

Re: Vizio SV420M has amber light, wont respond to power button or remote

i will try it, but what's the science behind this technique?
oh and how do i tell which IC is the eeprom?

edit: on shopjimmy they list the eeprom and say its u14 but how would i tell if SJ didnt have the eeprom for sale?

[triplefour]

Re: Vizio SV420M has amber light, wont respond to power button or remote

ok i tried freezing the chip, and turning the tv on, but it didnt change anything. also it leaves water on the board...that cant be good, can it?

[R_J]

Re: Vizio SV420M has amber light, wont respond to power button or remote

Sometimes the chip goes bad, who knows what happens inside, but I have used this method many times. In fact I removed an ic, read it and the data was bad and would not verify, freezing the ic I was able to read & verify the data, I then programed a new ic and the tv worked fine.
That little bit of condensation won't effect anything.
Also you need to have the tv un-pluged, then freeze the ic, then plug in the tv as the ic is read when the tv is first pluged in.
The ic will be near the main microproccessor, usually 8 pins, numbers like W25Q128fv or similar are common
This does NOT always work, if the eeprom (spi) chip is totally bad.

[triplefour]

Re: Vizio SV420M has amber light, wont respond to power button or remote

thanks for the explanation. i tried it but it still doesnt work. this does not tell me for sure that i have a bad eeprom tho...how can i be more sure of what the problem is? ive never dumped or programmed the eeprom before...what tools do i need?

[R_J]

Re: Vizio SV420M has amber light, wont respond to power button or remote

In this case the only way to know would be to replace the eeprom, there are small cheap usb reader/programers like the CH341A but you would need a copy of a working eeprom to program a new one.
I know the E371E and the E390-A1 had eeprom problems, I can't say if your board had that issue. but if Shopjimmy offers the chip, its a good chance thats the problem.

[triplefour]

Re: Vizio SV420M has amber light, wont respond to power button or remote

well i might as well try it. i should add the ability to read and write eeproms to the list of things i could try on future tvs anyway even if it doesnt work here.
is there a repository somewhere for these eeprom dumps?

[triplefour]

Re: Vizio SV420M has amber light, wont respond to power button or remote

I still have this TV but never did actually buy the eeprom.

http://www.shopjimmy.com/vizio-sv420...eprom-only.htm

does it come already programmed, or do i have to buy it, and then program it myself?

the board is 100$ and there is only one on ebay


ill ask again as well: is there a repository somewhere for eeprom dumps?

[vinceroger69]

Re: Vizio SV420M has amber light, wont respond to power button or remote

you can check the eeprom dump thread,
https://www.badcaps.net/forum/showthread.php?t=59877
the eeprom will come pre programmed so just solder on the board as should fix your problem if thats whats at fault, if you have a eeprom reader maybe copy the data first and possibly share it in the eeprom dump thread if your willing too.

[triplefour]

Re: Vizio SV420M has amber light, wont respond to power button or remote

thanks for the reply. i ordered the CH341A , and i plan to order the eeprom soon. if it doesnt exist in the dump thread i will try to add it.

just a thought: if i remove the eeprom chip and use the reader to read it, and it reads correctly, doesnt that mean i shouldnt actually replace the eeprom as i will just be wasting my 15$ ?

[vinceroger69]

Re: Vizio SV420M has amber light, wont respond to power button or remote

it may read but who knows if the data is correct on it? you would need a working eeprom too match all the data i guess and if eeprom does not solve your issue you could always re sell it i guess.

[triplefour]

Re: Vizio SV420M has amber light, wont respond to power button or remote

ok i will probably give it a go. and it looks like no one has dumped this eeprom (not in that thread anyway) so i will hopefully have something to add soon.