Panasonic Viera TC-L32U22 no picture

[Redrum]

Re: Panasonic Viera TC-L32U22 no picture

got it: power off (unplugged), standby (plugged in wait a few seconds), power on (press power, wait for the "click" and the backlight glow).

Understand state changes.

I'll take a few more thorough measurements later today...

Jim

[Redrum]

Re: Panasonic Viera TC-L32U22 no picture

OK, I have managed to convince myself of one thing. I don't understand the power distribution scheme or mechanism, so I don't understand what's going on, what controls what.

I had assumed that the PS board produces the 12v which IC4800 converts to AVDD13.7V and DVDD2.5V. I had further assumed that PANEL_VCC_ON and VDD25_EN are the respective enable lines to allow IC4800 to generate the voltages.

I am assuming (for now, by inferring from the block diagram) that PANEL_VCC_ON controls AVDD31.7V and VDD25_EN controls DVDD2.5V.

So, the measurements:

Nothing at plugged in and power off.

The power on sequence - press power button - a few seconds - click - a second, back light comes on.

None of the voltages are present until the click. At/after the click:

Tcon12 (pins 12, 13, 23, 38, 37) = 12.0V <expected>
AVDD13.7 (pin14) = 0.5V <expect higher>
DVDD2.5 (pins 32, 33) <expected, note that this occurs after click, at backight>

logic lines:
PANEL_VCC_ON = 3.0v <logic true for the 13.7 panel voltage?>
VDD25_EN = 3.0v <logic true for backlight maybe?>

so, my conclusion, again, not knowing the mechanism or, if this is even why the display does not turn on is this:

With 12v to the IC, and the logic true turning on the 2.5V, why isn't the other logic true turning on the 13.7V (measured at IC pins)

I could not find the SOS on the schematic although it is shown on the block diagram.

Finally, in the interest of cause and effect. This TV worked fine, then travelled 4 hours on the NYS Thruway, then plugged in power on, did I see the screen initially? Don't remember. That is why I initially thought to open up and reseat connectors, which I did.

This has been fun, but I am close to buttoning up the body and take it to the morgue.

Jim

[nomoresonys]

Re: Panasonic Viera TC-L32U22 no picture

OK, I have managed to convince myself of one thing. I don't understand the power distribution scheme or mechanism, so I don't understand what's going on, what controls what.

I had assumed that the PS board produces the 12v which IC4800 converts to AVDD13.7V and DVDD2.5V. I had further assumed that PANEL_VCC_ON and VDD25_EN are the respective enable lines to allow IC4800 to generate the voltages.

I am assuming (for now, by inferring from the block diagram) that PANEL_VCC_ON controls AVDD31.7V and VDD25_EN controls DVDD2.5V.

So, the measurements:

Nothing at plugged in and power off.

The power on sequence - press power button - a few seconds - click - a second, back light comes on.

None of the voltages are present until the click. At/after the click:

Tcon12 (pins 12, 13, 23, 38, 37) = 12.0V <expected>
AVDD13.7 (pin14) = 0.5V <expect higher>
DVDD2.5 (pins 32, 33) <expected, note that this occurs after click, at backight>

logic lines:
PANEL_VCC_ON = 3.0v <logic true for the 13.7 panel voltage?>
VDD25_EN = 3.0v <logic true for backlight maybe?>

so, my conclusion, again, not knowing the mechanism or, if this is even why the display does not turn on is this:

With 12v to the IC, and the logic true turning on the 2.5V, why isn't the other logic true turning on the 13.7V (measured at IC pins)

I could not find the SOS on the schematic although it is shown on the block diagram.

Finally, in the interest of cause and effect. This TV worked fine, then travelled 4 hours on the NYS Thruway, then plugged in power on, did I see the screen initially? Don't remember. That is why I initially thought to open up and reseat connectors, which I did.

This has been fun, but I am close to buttoning up the body and take it to the morgue.

Jim

Guess its possible that the move knocked loose a connection, maybe try plug and unplug all connections a couple times.

[Redrum]

Re: Panasonic Viera TC-L32U22 no picture

Guess its possible that the move knocked loose a connection, maybe try plug and unplug all connections a couple times.

Yea, that's what I originally thought but I did reseat all connections. After that all of this testing has taken me down this rabbit hole where I know what I am seeing isn't right, but not sure if I am seeing the smoke or the fire.

Jim

[nomoresonys]

Re: Panasonic Viera TC-L32U22 no picture

Very strange that it worked fine til the move, wonder if it might have gotten a slight crack in the screen.

[Redrum]

Re: Panasonic Viera TC-L32U22 no picture

Very strange that it worked fine til the move, wonder if it might have gotten a slight crack in the screen.

but at this point I am not seeing any voltages leaving the a board and going to the screen. I usually think cause and effect (broken due to transport), but perhaps it was coincidence.