Vizio E421VA - no picture

[VividElectrode]

Everyone has been infinitely helpful thus far in helping me diag some sets I have laying around needing repair. Your assistance is MUCH appreciated. Here is another one!

Model: Vizio E421VA
Issue: no pic / no sound

This set will power on. The backlight comes on for about 3 seconds, then goes off for about 3 seconds, then comes back on and stays on. The set is on the whole time, it's just the backlight that cycles once. (May be part of the normal startup, not sure). I can use the power button to turn the set back off, so it's responding to the buttons. However menu, ch, vol, etc produce nothing on the screen. I have tried to cycle through the inputs to see if I am getting sound with no luck, so assuming no sound either.

I have checked all fuses, including surface mount fuses on main board. all are ok. (unless I'm missing one I didn't see. I found F701 and F702). I don't see any visibly bad capacitors or any other visible failures.

Here are pictures of the power and main boards. I'm thinking this is a main board issue but am providing a pic of the power board just in case.

thank you in advance!

[budm]

Re: Vizio E421VA - no picture

Pictures of the whole back side of the TV so we can see all the boards?
Check the T-CON fuse for Voltages?

[VividElectrode]

Re: Vizio E421VA - no picture

Here is a picture of the whole backside of the tv. The T-con has a metal shield soldered to it, so it's someone hard to see, but I'm not having any luck finding a fuse on it. Should I get that shield off there?

[budm]

Re: Vizio E421VA - no picture

You need to remove the shield to see the components on the board.
http://www.shopjimmy.com/vizio-cbpft...1-pc-board.htm

[VividElectrode]

Re: Vizio E421VA - no picture

Alright. I removed the shield. Here are pics of the front and back of the tcon. I still can't find a fuse on it. Am I just missing it or is there no fuse on this one?

Thanks!

[budm]

Re: Vizio E421VA - no picture

OK, it looks like the Voltages are fed into the connector CN4402 without fuses, I see at least 2 input filter caps: C4402, and C4405, so check the DCV on the positive legs of those 2 caps with ref to chassis GND.
There is a ferrite bead FB4401 on the LVDS connector so see what DCV you have on that FB4401.
Very good pictures by the way.

[VividElectrode]

Re: Vizio E421VA - no picture

Thanks about the pix. Would you believe they were taken on a cell phone? haha
Alright:
C4402: 11.93V
C4405: 5.01V
FB4401: 11.88V

[budm]

Re: Vizio E421VA - no picture

OK, you do have Voltages (12V and 5V) to run the board.

[VividElectrode]

Re: Vizio E421VA - no picture

Yes. On the power board output, the 5V pins read 5.0V, the 12V pins read 11.9V, and the 24V pins read 25.0V

[budm]

Re: Vizio E421VA - no picture

Well all the running Voltages are present, so it is either the main board is not sending the signals to T-CON board or the T-CON board is dead even though it is getting the power.
You may want to contact shopjimmy to see if they have seen this problem with this model before.

[VividElectrode]

Re: Vizio E421VA - no picture

Hmm. ok. Any further testing I can perform to pinpoint the issue? Or at least which board is bad? In either case, is it most likely not something that can be fixed easily at component level and would warrant a board swap? I'm somewhat comfortable with SMD soldering.

[budm]

Re: Vizio E421VA - no picture

If you have he scope then you can probe the LVD signals going to the T-CON to see if they are present.

[VividElectrode]

Re: Vizio E421VA - no picture

Ok. I don't have an o-scope but plan on picking one up in the future. so, short of checking for the presence of signals, im pretty much at a board swap stage then? In that case, in your opinion do you think it would be more likely that the Tcon is bad or that the main board is bad? or is it just about a toss up as to which board to try first

[budm]

Re: Vizio E421VA - no picture

OK, I forget to ask you to remove the cable from the main board to the T-CON board and see what will happen, see if the backlights will stay on.
Also try removing the two white flat cables going to the panel to see what happen also.

[VividElectrode]

Re: Vizio E421VA - no picture

There are 2 cables going from the Tcon to the motherboard. the small one on the right side and the larger one on the left. Heres what happens:

Small disconnected, large connected. Won't power on. no backlights.
small connected, large disconnected. Powers on, backlights on.
Both disconnected. Powers on, backlights on.

With both of the Tcon-Main cables still connected, removing one of the ribbon cables to the panel makes 1/2 of the screen go white and the other half black. With the white half being the corresponding side to the disconnected cable. With both ribbon cables disconnected the screen is all black, backlights on.

[fishmonkey]

Re: Vizio E421VA - no picture

I have the EXACT same problem. We had TV come in that didn't power on at all. We ordered new mainboard and now it lights up, goes off, then lights back up and stay on with no video. Tried cycling inputs ... nothing.

[tibimakai]

Re: Vizio E421VA - no picture

It can't be the EEPROM, on the mainboard?
http://www.ebay.com/itm/EEPROM-FOR-V...item3a8450610a

[fishmonkey]

Re: Vizio E421VA - no picture

I tried a new t-con... same problem.

[cypress123]

Re: Vizio E421VA - no picture

Has any one tried the EEPROM for this problem ? I have one with the same issues also, I tried another T-con - no change

[cypress123]

Re: Vizio E421VA - no picture

continuing to probe - I have 0V on FB4401 - I had thought the 12V was the same and didn't check FB4401