Vizio VW42LFHDTV10A Dies after a few minutes

[hrabbot]

I've got a Vizio VW42LFHDTV10A that has two issues (maybe related?). The first issue is that it sometimes will not power on the backlight. An on/off cycle or two always causes it to come on.

After it's powered on successfully, it will function normally for between 10 and 30 minutes, then spontaneously powers off (and LED vizio logo goes completely dark). The sound dies also. The TV cannot be powered back on until the power cord has been removed and replaced. When I remove the power cord, then immediately reinstall it, the logo glows amber like normal, and it can be turned back on. If the TV hasn't cooled off since the last time it spontaneously died, it will not stay on very long at all after the unplug/replug remedy.

I opened the case, and inspected the components visually. I did not see any visibly bulged, leaking, or popped caps, and didn't notice any burned components or signs of heat or arc damage. I had to put it back together so that I could have my living room floor back, and didn't do any more in-depth poking around. After the initial discouragement, I've now regained my drive to fix this thing.

I haven't been able to find any threads talking about this same behavior, and I'm wondering where to begin diagnosing. I have a Southwire 11060S multimeter, which seems like it would be enough to check things out.

Thanks!

[hrabbot]

Re: Vizio VW42LFHDTV10A Dies after a few minutes

Any thoughts? I've found that a cooler indoor temperature seems to make it stay alive longer.

[cliff_hootarski]

Re: Vizio VW42LFHDTV10A Dies after a few minutes

Have you looked at the caps on the inverter boards? Also not being able to turn the TV back on unless you unplug it, indicates to me a main board problem. Vizio had a problem with voltage regulators on the main boards.

[CapLeaker]

Re: Vizio VW42LFHDTV10A Dies after a few minutes

Put some heat (hair dryer) on the main board and see if you can make it act up faster.
Since more heat makes it shut down faster, it isn't capacitor related. So my bet is on the main board for now on what you are describing. Heat and cool (can of air upside down) the EEPROM IC. See what you get.

[hrabbot]

Re: Vizio VW42LFHDTV10A Dies after a few minutes

I'll take a look at it again, but I didn't see any swollen caps. Any tips on finding info on the regulator problem?

[hrabbot]

Re: Vizio VW42LFHDTV10A Dies after a few minutes

Put some heat (hair dryer) on the main board and see if you can make it act up faster.
Since more heat makes it shut down faster, it isn't capacitor related. So my bet is on the main board for now on what you are describing. Heat and cool (can of air upside down) the EEPROM IC. See what you get.

Nice! That's a good idea. I didn't realize bad caps wouldn't be affected by heat. Is there a IC number I should be especially looking at? I haven't found much info on this particular TV.

[CapLeaker]

Re: Vizio VW42LFHDTV10A Dies after a few minutes

bad caps ARE affected by heat. The heat lowers the ESR value, so when you heat a bad cap up, it will work as long as it stays warm. But this is exact the opposite what you are describing.

Got no idea on what the IC number is. You didn't post any pictures. Post a high resolution, straight shot picture of YOUR mainboard. Then we can find the EEPROM.

[CapLeaker]

Re: Vizio VW42LFHDTV10A Dies after a few minutes

Look if your main board has a U29. Its a 16 pin IC, next to the LVDS connector.

[hrabbot]

Re: Vizio VW42LFHDTV10A Dies after a few minutes

16 pin U29 - yes. MB pic attached.

[hrabbot]

Re: Vizio VW42LFHDTV10A Dies after a few minutes

I've got a zillion little stick-on raspberry pi heat sinks, think I should strategically stick those on some components?

[cliff_hootarski]

Re: Vizio VW42LFHDTV10A Dies after a few minutes

Try suggestion in post #4 on U29, see if it changes symptoms.

[hrabbot]

Re: Vizio VW42LFHDTV10A Dies after a few minutes

air cooling with a tiny fan seems to have lengthened the run time. Unfortunately, I'm having a hard time finding that component.

[cliff_hootarski]

Re: Vizio VW42LFHDTV10A Dies after a few minutes

Has the sticker with VW42LF WUN printed on it.

[hrabbot]

Re: Vizio VW42LFHDTV10A Dies after a few minutes

Has the sticker with VW42LF WUN printed on it.

Sorry, what I meant was that I'm having a hard time sourcing a replacement. Probably just going to swap the mainboard.

[cliff_hootarski]

Re: Vizio VW42LFHDTV10A Dies after a few minutes

Test those voltage regulators first, might be a cheap fix.

[hrabbot]

Re: Vizio VW42LFHDTV10A Dies after a few minutes

good call. You talking about the large 3 leg ICs?

[CapLeaker]

Re: Vizio VW42LFHDTV10A Dies after a few minutes

air cooling with a tiny fan seems to have lengthened the run time. Unfortunately, I'm having a hard time finding that component.

Look here:
http://www.shopjimmy.com/catalogsear...=VW42LFHDTV10A
$15 and they have some available.

[cliff_hootarski]

Re: Vizio VW42LFHDTV10A Dies after a few minutes

Check U44,U17,U21 and U22? all LVDO(low voltage drop out) voltage regulators.
Check their voltage while the TV is operating properly vs when it shuts down.
We need the voltage on all three legs. Please report it this format:
Uxx (Also part number written on the chip)
operating not operating
Pin 1 x.xxvolts x.xxvolts
Pin 2 x.xxv x.xxv
Pin 3 x.xxv x.xxv
Positive DC probe to the chip, Negative DC probe to chassis.
That eeprom chip $15 at Shopjimmy.
(board number 3642-0412-0150)

[hrabbot]

Re: Vizio VW42LFHDTV10A Dies after a few minutes

Finally got it taken apart again and got these voltages. I'm assuming Pin1 on these is leftmost when the large solder tab is oriented upward.

Listed as Operating voltage first, after-failure voltage second.
U44:
Pin1 8.31V 0V
Pin2 9.57V 0V
Pin3 11.47V 0.15V(bleeding down)

U17:
Pin1 2.10V 0.00V
Pin2 3.36V 0.01V
Pin3 5.16V 0.35V(bleeding down)

U21:
Pin1 0V 0V
Pin2 1.26V 0V
Pin3 2.50V 0V

U22:
Pin1 2.08V 0.00V
Pin2 3.34V 0.00V
Pin3 5.20V 0.00V

Hope this contains some useful data.
Thanks.

[hrabbot]

Re: Vizio VW42LFHDTV10A Dies after a few minutes

Interestingly, U22 has voltages on all 3 pins while the TV is plugged in but not turned on (approximately as in the operating state). After failure, they are 0 as noted.