Panasonic TH-42PE7u - no blink code, no video, no audio

[ngth82]

Hello everybody!

I have a Panasonic TH-42PE7U 42" Plasma TV that died yesterday. The unit was manufactured October 2007. When turn the power on, I hear a few clicks - I'm assuming this is the relays energizing. When I press the power button on the front of the unit, the red LED is solid red and does not blink. The remote does not work - the unit does not respond to turning it on, or off. If I press and hold down the power button for a few seconds, I hear the relays click (off?), then back on a moment later.

Anyway, I was able to find the TH-42PE7U service manual from this site. I removed the back panel and checked the following so far:


Power Board - TNPA4221 AK
1. Verified that 120V was coming in on the line across P9.
2. Verified that fuses F401, F402, F403, PR401 and PR601 are intact.
3. Verified that probe location ZH150 (at diode D420) shows a peak voltage of about ~390V when I initially plug the unit in, then goes down to ~160V and maintains that voltage.
4. Q406 does not show a dead source between the source/Gate, drain/gate, or source/drain.
5. PR401 shows continuity.
6. I measured P11 and P2... Vsus = 0V.
7. I tried measuring across P11 and P2 again with the wires to SC2 and SC11 disconnected. This yields Vsus = 0V.


This TV does not have a blink code at all. I was hoping for *some* quick indication with the LEDs, but no dice. Where do I go from here? Any help would be greatly appreciated.

Thank you,
Thomas

[ngth82]

Re: Panasonic TH-42PE7u - no blink code, no video, no audio

I forgot to mention that i went through the Power State Diagrams in Section 9.3 - Fuses F401, F402, F402, PR401 and PR601 were verified to have continuity.

I figured, i should follow Section 9.4 - No Picture. The state diagram indicates that I should look for the SC board LED (D6583 - green) and SS board LED (D6253 - green), but these both do not illuminate. It appears that I also am missing +15V on connectors P6 and P12

[Moreno83]

Re: Panasonic TH-42PE7u - no blink code, no video, no audio

The "No picture" is only when the tv is on. The tv is not on , its in standby.

Did you try to change channels with the buttons on the tv? So turn on the tv and then use source/menu etc.

[ngth82]

Re: Panasonic TH-42PE7u - no blink code, no video, no audio

Good morning Moreno83 -

Yes, i have tried using the buttons on the front of the TV - channel changes still show a black screen. The same goes for pressing the input selector button.

The "input" OSD in the upper left does not show up at all - the plasma display is not getting power.

[Moreno83]

Re: Panasonic TH-42PE7u - no blink code, no video, no audio

Goodmorning/Afternoon!

Does the tv turn on with a green led or is it always in standby mode with a red led? Im suspecting a bad mainboard but ill wait for the other guys to jump in.

[ngth82]

Re: Panasonic TH-42PE7u - no blink code, no video, no audio

Hi Moreno83 -

When operating normally, the TV does not have a green LED on the front panel -- it's always been red. Either it's "off" when the TV is off, or it's "red" when the TV is on.


-Thomas

[ngth82]

Re: Panasonic TH-42PE7u - no blink code, no video, no audio

Can someone please help?

@Moreno83 - you suspect a bad mainboard -- which board identifier are you referring to?

Thank you.

[Moreno83]

Re: Panasonic TH-42PE7u - no blink code, no video, no audio

Hi Thomas ,
The tv is not turning on , my opinion is thats either the powersupply or the mainboard. ( A board ).

Do you get a blink code when you remove the SC20 cable and turn the tv on ?

[ngth82]

Re: Panasonic TH-42PE7u - no blink code, no video, no audio

Thank you Moreno83. I'll check that section and see what I can deduce.

-Thomas

[Moreno83]

Re: Panasonic TH-42PE7u - no blink code, no video, no audio

Sorry , my knowledge is not that great as others on this forum. I don't know this tv , the panasonics that i repaired are from 2008 and later and have a green led when turned on.

Just logical thinking tells me that if the PS was bad , you would get a blinking led. Bad SC board also gives a blinking led ( normally ).

The fact that you don't have any Vsus voltage at all and no sound makes me think that the tv is in standby mode and does not turn on. ( which activates Vsus/picture ). Does the tv respond to the remote? ( for example power button on remote ).

[ngth82]

Re: Panasonic TH-42PE7u - no blink code, no video, no audio

Hi Moreno83 - I understand. I do appreciate the tips thus far though. Thank you.

The TV does not respond to the remote (power, channel, volume, etc)

I'll have to try and remove the SC20 cable that you suggested a day ago and see if that makes any difference. I haven't tried to disconnect anything between the "D" board or the "SC" board yet. I'll report back on this.


One question: when do the relays normally click? Do they click when the TV is initially plugged in, or do they click after you have pushed the power button? I don't recall how my TV behaves when it is operating normally -- I'm assuming it should be relays clicking when you press power.

I ask because:
1) I'm noticing that the relays click twice when I plug it in.
2) It doesn't do anything when I press power
3) it clicks (1-click) "off?" when I press and hold the power button for a few seconds.

[Moreno83]

Re: Panasonic TH-42PE7u - no blink code, no video, no audio

So when the power button is pressed the red light stays red , right? When you press the powerbutton on the remote , does the led blink? ( as responding to the remote ).

The relais on the panasonics i know will go " click click " when you press the power button and then the green led illuminates. It will then click again 1 time when its active. It will click 2 times when its detecting a error. ( turns off ).

[ngth82]

Re: Panasonic TH-42PE7u - no blink code, no video, no audio

So when the power button is pressed the red light stays red , right? When you press the powerbutton on the remote , does the led blink? ( as responding to the remote ).

Correct, when i press the power button, the red LED illuminates, and stays red -- no blinks.

When i press the power button with the remote, nothing happens. The LED does not turn on... nothing.

[ngth82]

Re: Panasonic TH-42PE7u - no blink code, no video, no audio

I haven't tried to disconnect anything between the "D" board or the "SC" board yet. I'll report back on this. .

I tried disconnecting the SC20 cable. This did not change the behavior of the TV.

[ngth82]

Re: Panasonic TH-42PE7u - no blink code, no video, no audio

I was tinkering around and disconnected A5 from the TV (all the other cables were plugged back in). The display turned on and was solid white! The power supply's board appears to be "good" I think.


The A5 connector has a 10 bit LVDS bus from the digital video processing block (ic8001) and some control signals (panel_stby_on) that appears to be interesting. I might do some more digging later....

[tw2005]

Re: Panasonic TH-42PE7u - no blink code, no video, no audio

I was tinkering around and disconnected A5 from the TV (all the other cables were plugged back in). The display turned on and was solid white! The power supply's board appears to be "good" I think.


The A5 connector has a 10 bit LVDS bus from the digital video processing block (ic8001) and some control signals (panel_stby_on) that appears to be interesting. I might do some more digging later....

I don't have time right now to have a dig but that is a test procedure on the earlier sets which proves the sustains and P are good. i suspect since this turns on with the main isolated the mainboard could be the prime suspect . But could be D as well.

Not sure how applicable this guide may be but have a read. has also No display/No OSD flowchart too which has the A5 disconnection.

Also buried in there is the A5,A6,A7 also white screen procedure, you may have to follow a few different charts to what's what.
I don't a lot of experience either of these earlier sets more with the newer models with just the A-boards

[ngth82]

Re: Panasonic TH-42PE7u - no blink code, no video, no audio

That is a wealth of wonderful information! I'll try and go through the guide tomorrow. Do you have one specifically for the TH-42PE7U?

Thank you,
Thomas

[tw2005]

Re: Panasonic TH-42PE7u - no blink code, no video, no audio

That is a wealth of wonderful information! I'll try and go through the guide tomorrow. Do you have one specifically for the TH-42PE7U?

Thank you,
Thomas

Nope but that guide looks like it may be on the money as the D-board in yours is the same as

Panasonic
TH-42PC77U TH-42PE77U TH-42PE7U TH-42PX75U TH-42PX77U

It's the A-board that's different and different board number

Now it appears phsically both would bolt in but the problem may end up being cabling looking at the positioning of the connectors. i suspect some of your leads may not reach but you'd have to do a fair bit of studying of pin outs to be sure they were the same if you wanted to experiment using a different A-board.

It won't have all the same features though

there is 2 boards I could find http://www.ebay.com.au/itm/Panasonic...item3cff577c96

At $120 it's in the ball park as I expect a repaired one will be about the same. Moduslinkpts do repairs but don't list yours but i suspect if you made an enquiry chances are they'll still be able to do it.

this one is a little cheaper with offer so you may get it down and 100% feedback on over 2000 items

http://www.ebay.com/itm/PANASONIC-TH...item3cffc0c428

[Moreno83]

Re: Panasonic TH-42PE7u - no blink code, no video, no audio

Im also suspecting a bad mainboard.

[Moreno83]

Re: Panasonic TH-42PE7u - no blink code, no video, no audio

Hi Thomas ,

Any luck with the tv?