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

[ngth82]

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

Hi Thomas ,

Any luck with the tv?

Hi Moreno83 -

As luck would have it, I found a nearly identical and fully functioning TV (a TH-42PX75U) on the local ad site here and bought it for $100USD today -- about the same price as chancing it with a replacement A-board off of eBay. I haven't taken the back cover off of the new TV yet, but as far as I can tell from looking through the vent holes, the parts appear to be the same.

With that said, I think I want to continue with trying to get a replacement A-board or fix the A-board for the broken TH-42PE7U.

Out of curiosity, does anyone have any experience in debugging the A-board? I'd like to get down to the component level debugging, if possible.



Thank you for the help so far guys. I really appreciate it.

-Thomas

[Moreno83]

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

Nice! Thats a cheap tv.

Could you try and replace the A board from the replacement tv? Just so we know that that was the fault. ( Everything points to it... ).
Trying to find the fault on the A board is very hard! You need the schematic and just follow the voltage lines until it stops. It can be a simple fault as a EEPROM....

[ngth82]

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

Nice! Thats a cheap tv.

Could you try and replace the A board from the replacement tv? Just so we know that that was the fault. ( Everything points to it... ).
Trying to find the fault on the A board is very hard! You need the schematic and just follow the voltage lines until it stops. It can be a simple fault as a EEPROM....

That was my initial thought as well. I'll have to find some time to do that. I'm currently leaning towards selling my broken TV, or taking a gamble and just purchasing an A-board if i find one for dirt cheap. The replacement 42" TV works. Lol.. i'm not entirely wanting to take it apart at the moment though .

Now with regards to the busted A-board... I found the service schematics from this site. That's the easy part. I'm thinking one of the BGA devices may have blown. If that is the case, that would be prohibitively costly to replace (and increasingly difficult to find replacement parts, especially if it is a custom device.)

[ngth82]

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

Hi Guys -

Just following up. I was able to trace the issue back to the IC1100 component. I worked from the beginning of the attached slide deck until the problem was discovered.

The PANEL_STBY_ON signal from IC1100 does not assert high to the base of Q4015, Q4014 does not turn off, and no output voltage (2.5V) is seen at Connector A5/D5 pin 20. (See Slide 47 of the attached PDF). This is highly indicative that the A-board is the problem (and confirms our suspicions from earlier).

Now, i'm curious if anyone has any experience in repairing A-boards that can give me any pointers or additional suggestions before i purchase a new part for IC1100? I can replace the part just fine as i have the soldering equipment and I worked with fine pitch parts many times during my engineering career.

The device has the marking:

Panasonic
MNZSFD7G
735P72CD
P P42


Looks like I found the part online for a few bucks from: http://www.utsource.net/ic-datasheet...2-1887922.html

Are there any resellers that are more reputable over another? Obviously not a Digikey or a Mouser site

[ngth82]

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

Nice! Thats a cheap tv.

Could you try and replace the A board from the replacement tv? Just so we know that that was the fault. ( Everything points to it... ).
Trying to find the fault on the A board is very hard! You need the schematic and just follow the voltage lines until it stops. It can be a simple fault as a EEPROM....

Hey Moreno83 --- i ended up replacing the A-board. Yes, it was the issue!