Re: Panasonic Plasma TV LED blinking 12 times
Success.
I fitted a replacement P board and it's all working again.
Shame I replaced the H and DG boards first. I put the originals back in so if anyone needs a H or GD board, let me know.
All the best to all on the Forum who helped to diagnose the problem.
PaulF
Member
Last Activity: 01-30-2014, 01:42 PM
Joined: 01-15-2014
Location: Oakham
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Re: Panasonic Plasma TV LED blinking 12 times
I was thinking along the same lines as you abou injecting a voltage into MC351 pin 4 but was a bit nervous of doing it in case the reason for it being absent at the moment was for protection due to a fault elsewhere, if I inject a voltage I could cause more damage.Leave a comment:
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Re: Panasonic Plasma TV LED blinking 12 times
I think pin 8 of MC701 is the sensing signal for the 15v supply so what I measured could be correct.
It seems like MC701 is not giving the signal to turn on the 15v to the H board, wether thats due to a fault on MC701 or due to it thinking there is a fault elswhere is difficult to know.
Without knowing what all the pins should read it could be difficult to know if things are right or wrong.
I'll have to decide if it's worth risking buying another P board (I've located one for about £60) or havee a trip to the local...Leave a comment:
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Re: Panasonic Plasma TV LED blinking 12 times
Just studied tthe diagram again. I have 15v at TP7. Between pin 8 of MC701 and TP7 are: R367, R351 and and unidentified symbol. Will check through that part of circuit.Leave a comment:
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Re: Panasonic Plasma TV LED blinking 12 times
You could be on to something there. Just checked pin 8 of MC701 and it gets up to 3.2v only. Will lift the board out and check IP351 as you suggested.Leave a comment:
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Re: Panasonic Plasma TV LED blinking 12 times
Typo: Should have been 15v at D and no 15v at SLeave a comment:
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Re: Panasonic Plasma TV LED blinking 12 times
TP2302 does indeed go high to flag the SOS.
I nonitored the G-S voltage of mosfet Q351 with a scope, this never rose above a fraction of a volt during switch on & just looked like noise. This obviousy isn't sufficient to turn the device on hence 15v at D and no 15v at D.
I then monitored pin 4 of MC351 which is marked 15V_ON, which i assume is the signal to turn Q351 on, this remained constantly 0. This in turn comes from MC701.
I am probably at the point now where I am beginning to condider that I'll have to...Leave a comment:
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Re: Panasonic Plasma TV LED blinking 12 times
Doh,
Sorry, will have to get some glasses. even when I saw it in your message I read it as 5 instead of S. Good job there is someone around to put me right.Leave a comment:
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Re: Panasonic Plasma TV LED blinking 12 times
The voltage increases gradually over a couple of seconds and reaches a max of 1.56v which is steady for probably about a second then shuts off. Will do the test again and take better note of what happens. tw2005 I agree with what you are saying, I'll check out Q2301.
I did identify the FET as 25K2510, I just can't seem to find a data sheet for it to see it's spec in case it is faulty and need to find an equivalent.
Thanks for the help guys.Leave a comment:
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Re: Panasonic Plasma TV LED blinking 12 times
Further tests show that I have 15v at TP7 which is upstream of Q351 FET which appears to switch the 15v to P6 pins 1-4. I plan to investigate further at the weekend when I can borrow a probe from work which is small enough to get onto the gate to see if the gate drive is ok.
I have not yet been able to identify the FET from it's number NEC 25K2510.Leave a comment:
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Re: Panasonic Plasma TV LED blinking 12 times
I've done the tests as you suggested and at H3 pins 21-23 & P6 pins 2-4 the voltage only rises to 1.56v max before it is tripped off. Looks like it could be the +15v from the P board? I assume this voltaage is reference to the chassis ground?Leave a comment:
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Re: Panasonic Plasma TV LED blinking 12 times
Thanks for the reply, yes you are absolutely right about the boards. I'll do the checks you suggested and hope I can trace the board where the fault is. Thanks for the link to the manual, it's a great help, was trying to use a manual for a similar set but had an A board instead of the H & DG boards which is why I replaced them both.
If it's the P board I can get a replacement but want to be sure before I go ahead, looks like I've already replaced 2 unnecessarily.
Thanks again for taking the trouble to help.Leave a comment:
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Re: Panasonic Plasma TV LED blinking 12 times
I've just replaced the A board (2 boards to be exact TNPA4177 and TNPA4226) and the problem is still the same, ie 12 blinks. Any ideas where the problem can be now?Leave a comment:
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Re: Panasonic Plasma TV LED blinking 12 times
Following checks on the speakers & wiring I have ordered a replacement 'A' board.
Are there any adjustments required following fitting of this board? i have most basic test equipment eg. multimeters, oscilloscope etc.Leave a comment:
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Re: Panasonic Plasma TV LED blinking 12 times
Thanks for the info Tom66.
Good job I asked, thought it was the power board.
I'll investigate and post my findings.
Much appreciated.Leave a comment:
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Panasonic Plasma TV LED blinking 12 times
My Panasonic TH-50PX70B TV has developed a fault indicated by the red LED blinking 12 times. I have searched the internet and the blinking LED fault codes seem to differ between models. From some comments on this forum I think it is most probably the power board.
If a can be sure it is this board I would be happy to replace it. it would be even better if I could repair it.
Does anyone have any more info on this model or can give me some pointers on tests to identify where the problem is. -
Re: New Members - please post your introductions here
Just want to introduce myself as a new member.
Name: Paul
Age: 55 ish
I am an electrical engineer by trade working in renewable energy, currently I design & develop new electrical and electronic products.
I am self taught in electronics, embedded firmware and PC software and will have a go at anything like most Engineers.
I like tinkering with anything electronic particularly if it involves fixing something.
In my spare time I do a lot of repair work on vintage aircraft electrical...Leave a comment:
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