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Jack
Jack, Technician
Category: TV
Satisfied Customers: 8343
Experience:  40 years experience as audio,video repair and installation tech
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Any idea what goes bad on the A boards in panasonic plasma

Customer Question

any idea what goes bad on the A boards in panasonic plasmas?
Submitted: 1 year ago.
Category: TV
Expert:  Jack replied 1 year ago.
Hello , thanks for the request .
Could be a number of things depending on the problem you have now .
What is the blink code for this problem ?
Customer: replied 1 year ago.
My problem is identical to the post I found here: http://www.badcaps.net/forum/showthread.php?t=30268
When the TV was given to me it had a swollen 220v/1400uf cap (one of the large ones on the power supply) which I have replaced.
I have no blinking lights, the screen lights up but remains black when I power the TV on, and I get no response from channel changing or menu buttons. Also the fans do not spin.
Internally, the green lights are on the large boards on each side, and I get 5v on P25 Pin 9 like I should.
I have reflowed the A board in an infrared reflow oven and it didn't change anything, so it's not a lead free solder/cold solder joint problem.
I've found replacement boards on ebay where the sellers are getting the cores and replacing the faulty part - so we're back to the original question... what actually goes bad? is it the IC that has the firmware? is there a particular FET or diode that likes to blow?
Expert:  Jack replied 1 year ago.
Yes , back to the original question and also back to the original answer ; could be a number of things and I simply don`t have that info .
Those guys most likely are or were Panasonic employee and have inside info .
Whats the board number ?
perhaps I can find something in the database I have access to .
Customer: replied 1 year ago.
TNPH0793 is the part number of the A board, with a suffix of AB for the revision.
I do component level repair on amplifiers for a living, so knowing what problem component to look for based on the symptom is something that gets picked up over time and experience. I was hoping the same theory applied to this field of repair.
anyhow, if you can find anything that points to which part actually goes bad I will be happy to consider the original question satisfied.
thank you!
Expert:  Jack replied 1 year ago.
Cannot find anything specific about the main board but there something I was thinking here .
Right now you assume that the main board is the culprit or you are certain of this ?
Without that blink code it is difficult to be specific but there is a voltage that may cause the problems you have now if missing .
Check on connector A25 for 15 volts just beside the 5 volts , that voltage is also standby and should be there .
You did not mention about that and that 15 volts get sub-divided in various voltages for the main board
Customer: replied 1 year ago.
I see connector P25 not A25, which is the one where pin #9 was 5v standby and while on. I probed all the wires on that plug in standby and while on and couldn't find voltage.
If it helps, when I plug the power cord in i hear 2 relay clicks and then a few seconds later 1 more.
There are probe points on the power supply, is there a diagram to show which points should have which voltages so I can test further?
Expert:  Jack replied 1 year ago.
Hello , was out when you repliedSorry , I need to correct something here , there is 15 volts at P25 when the tv is on but the standby F15 volts is at P6 >> A6 on main boardThe P6 is on the power board and where it connects on the main (A) board it turns into A6 so it is the same and should have a pin with 15 volts .Click the link here ; https://www.dropbox.com/s/fr7x5mauho96ub2/2015-07-09_1412.png?dl=0
Expert:  Jack replied 1 year ago.
Check that link above and also , here is the service manual for this ;https://www.dropbox.com/s/x86zrj2de0iqfqk/panasonic_tc-p46g10_chassis_gpf12du_sm.pdf?dl=0 Give it a minute to open and then you can download it to your pc
Customer: replied 1 year ago.
I just checked the manual. 15v is only supposed to be present while powered. I checked the correct pins and i'm getting 15v. This puts me right back to where I started, knowing the problem is with the A board - but not knowing which component tends to go bad on it.
Expert:  Jack replied 1 year ago.
Then you did not look at the link I gave you or looked good enough at the manual .There is a 15 volts that is switched (as I said above ) and a standby 15 volts called F15 , that F15 is needed by the main board.Look again or look at this link ;https://www.dropbox.com/s/d8divorxkwwm4rn/2015-07-09_1542.png?dl=0
Expert:  Jack replied 1 year ago.
Then you did not look at the link I gave you or looked good enough at the manual .There is a 15 volts that is switched (as I said above ) and a standby 15 volts called F15 , that F15 is needed by the main board. Look again or look at this link ; https://www.dropbox.com/s/d8divorxkwwm4rn/2015-07-09_1542.png?dl=0