Vizio E420-A0 LCD TV Repair Experience

[bluetrepidation]

Long time lurker here. I've been subbed to Dave's You Tube channel since April 4th 2009. I wanted to share a recent repair of a Vizio E420-A0 TV.

Symptoms:
- When powering on the power LED would light up.
- Black screen
- No back light
- No audio or popping
- Zero image on LCD when looking with a flashlight
- Pressing the power button to turn the TV off would result in nothing. The power LED would still be on. Only unplugging the unit would reset it to the off state.

Diagnostics:
Power supply first....
- 5.2 volt standby rail was ok.
- When powering up the main 12 volt rail comes up as normal.
- When jumping the 3.3v power on signal over to the LED back light pin the back light would flash momentarily while there was no PWM to command the brightness.

Moving to the mainboard....
- Checked the electrolytic caps on the board. Each cap seemed to have an appropriate voltage except a few at the top left of the board. These rails seem to be powered on by a MOSFET near the power plug.
- Jumped the MOSFET to force it on. Other caps became hot but still no image.
- MediaTEK CPU was warm to the touch.
- Flash chip was seeing it's 3.3 volt rail like it should.
Maybe the firmware has become corrupted and no longer can boot?

Since a new mainboard is $28 including shipping I went ahead and ordered one. In fact the board I needed was not in stock so I went with one for a TV with a bigger screen and an additional HDMI port (PN: 3647-0812-0150). Once installed the TV is back up and running.

So here is a question... From a build quality standpoint what make/model TV would you purchase today? Or are all of these things just a throw away item these days?

Thanks,
A.J.

[tec5c]

Not sure if the same policy applies in America, but I recently bought a TV with extended warranty. The policy here is if the set fails during the extended warranty period you have the choice between a) replace the TV with the current model b) replace TV with any other TV from any manufacturer of equal value c) get store credit for the original price you paid d) get all of your money back.

I am not sure if this is just the policy of the store where I bought my TV from or if it's standard.

My preference is Japan made Panasonic sets. While these are quite rare nowadays, they are beginning to get them back into the market.

[nanofrog]

Sadly, they are generally considered disposable by their respective manufacturers. Repairs are board swaps rather than diagnosing and repairing the actual fault; unless you're an EEVBlog forum member that is. 

Even the most expensive models from Samsung for example have ended up as eWaste (also resulted in very pissed off owners).   

[bluetrepidation]

Thanks for the reply guys. I'll keep my eyes out for a made in Japan set for sure. I'm not one to purchase the extended warranty since I tend to just deal with broken things myself.

A.J.

[BMack]

I work on a lot of TVs at my shop. Panasonic plasmas were my favorite. LEDs I really like Sharp and LG but for different reasons.

Sharp has a really good picture and a robust Delta power supply(Delta also supplies some Vizio models, usually the higher end). The nicest Sharps are sold as the Pioneer Elite.

LG I like because the picture is very good BUT the parts inside are crap, that's how they are very reasonably priced. Also the LG parts are normally really cheap, I've bought complete kits for under $30.

Samsungs always have this weird motion effect that you can't turn off, I just don't like them. They're really easy to diagnose, which is nice.

Vizio has a few series that suffer a LOT of bad panels. A lot of those panels are made by Sharp but it's not a panel Sharp puts in any of their Sharp sets.

BTW, the current Panasonic LEDs have a LG panel.