Panasonic TX-40CX400B - 17IPS20 - DULLSCREEN+ON/OFF/ON/OFF fault

[shepp]

Hi guys this has just come to me and im not too sure were I should be checking voltages etc.....Vestel board hahaha

I seem to have a voltage bouncing around but not sure if im checking in the right place see attached photo

the set powers up, the hmdi channel info comes up, then after a couple of minutes it will freeze then switch off and on again, its gradually got worse the more I do it......i.e the screen stayed on longer when it 1st started checking it

there is no signs of burning any where or shorts on the board

I have circle where the voltage is bouncing around, and also were there is a suspicious area in which the diodes read 0 both ways(not removed as of yet though)

wanted to check the voltage properly 1st

MAIN BOARD PINS
1= 23v[25V ON] 7=
2= 8=0
3= [3.26V ON] 9=0
4= [3.26V ON] 10=0
5= 11=12V
6=12V [11.9 ON] 12=12V

the ones that are blank are reading mV and moving around

Now all of a sudden the backlight is flickering a lot, but before I even took the cover off the set it looked very dull

[Andrew F. Ali]

Re: Panasonic TX-40CX400B - 17IPS20 - DULLSCREEN+ON/OFF/ON/OFF fault

Replace the PSU.....

[shepp]

Re: Panasonic TX-40CX400B - 17IPS20 - DULLSCREEN+ON/OFF/ON/OFF fault

Replace the PSU.....

hahahaha thanks for that amazing advice - not quite what I was posting on here for though

im more of a component kinda guy especially when the PSU is like £40

[Andrew F. Ali]

Re: Panasonic TX-40CX400B - 17IPS20 - DULLSCREEN+ON/OFF/ON/OFF fault

hahahaha thanks for that amazing advice - not quite what I was posting on here for though

im more of a component kinda guy especially when the PSU is like £40

OK, shepp...OK....If the diodes appear faulty....lift one end and re-test...then worry about voltages......from your questions I misinterpreted as you not having any knowledge...SORRY. my bad....

[shepp]

Re: Panasonic TX-40CX400B - 17IPS20 - DULLSCREEN+ON/OFF/ON/OFF fault

Pulled the biggest diode off today and it has gone 0 both ways, in the attached Pic of the 2 diodes.

the transformer in which they are connected is the 30068375 transformer not sure what that does but if its to do with the LED backlight then it would make perfect sense

[dick_barton]

Re: Panasonic TX-40CX400B - 17IPS20 - DULLSCREEN+ON/OFF/ON/OFF fault

When you replace the diode use the same type. That is, if its an ultrafast Schottky diode then replace with likewise.

[shepp]

Re: Panasonic TX-40CX400B - 17IPS20 - DULLSCREEN+ON/OFF/ON/OFF fault

Yes Ultrafast one.. MUR460G - £2 off ebay so ordered it.....then found the same ones on RS for 0.34p ....typical

[R_J]

Re: Panasonic TX-40CX400B - 17IPS20 - DULLSCREEN+ON/OFF/ON/OFF fault

Is this close? The values etc. do look different, but it might be similar
It seem a lot of mfg's use the board and stuff it differently

[shepp]

Re: Panasonic TX-40CX400B - 17IPS20 - DULLSCREEN+ON/OFF/ON/OFF fault

Is this close?

EXCELLENT Thank you

[shepp]

Re: Panasonic TX-40CX400B - 17IPS20 - DULLSCREEN+ON/OFF/ON/OFF fault

Right .... so ive changed the Diode and the screen is nice and bright now, but its still switching off rather quickly, it powers up, I press menu, scroll and then it freezes and switches off then powers back on and so the cycle begins

[shepp]

Re: Panasonic TX-40CX400B - 17IPS20 - DULLSCREEN+ON/OFF/ON/OFF fault

Is this close? The values etc. do look different, but it might be similar
It seem a lot of mfg's use the board and stuff it differently

some components are not on this schematic? is this correct? I cant find C283 C284 and I have no 5v Q212?

some things not quite adding up

[R_J]

Re: Panasonic TX-40CX400B - 17IPS20 - DULLSCREEN+ON/OFF/ON/OFF fault

This schematic is most likely for a different mfgr. Its the best available at this time, if parts are different or missing on your board, go by your board not the schematic. Many times they use the same pc board for different models ie 32" -50" and add or change parts accordingly
This is 17ips20 - (R2) <----
If its made for Panasonic, Hitachi, Vestel or anyone else its made to that mfg's specs Do search for this board using images and see the different configurations

[shepp]

Re: Panasonic TX-40CX400B - 17IPS20 - DULLSCREEN+ON/OFF/ON/OFF fault

ok sound advice, I dont think I read your original post properly before, my bad, problem now is figuring out why its rebooting, voltages look the same on the pins of the schemes anyway apart from there doesnt seem to be any 5v any where

this is gonna be one of them where I may have to guess which board is faulty and at this moment Im thinking it could be the Main Board not the PSU, but Its a vestel so its highly likely to be the PSU.......im getting the meter back out to investigate further, ill see if I can find any thing else out that might help someone to help me....or maybe find the fault hahahaha :-D

[R_J]

Re: Panasonic TX-40CX400B - 17IPS20 - DULLSCREEN+ON/OFF/ON/OFF fault

Is this the 5 volts standby you are missing? try and follow the line back, it must lead to a regulator ic or diode and then check if its supply is working, I can't see the main board even turning on without 5 volts standby

[shepp]

Re: Panasonic TX-40CX400B - 17IPS20 - DULLSCREEN+ON/OFF/ON/OFF fault

Is this the 5 volts standby you are missing? try and follow the line back, it must lead to a regulator ic or diode and then check if its supply is working, I can't see the main board even turning on without 5 volts standby

Q212 for the 5v isnt even on the board its empty check pic no.2 right bottom corner of yellow box

and I cant find any 5v signals, found a 3.3 and 12v and 24v, think the 3.3v is for the backlight control and thats it, im gonna run through the testing again tomoz and post results just in case they have changed

[shepp]

Re: Panasonic TX-40CX400B - 17IPS20 - DULLSCREEN+ON/OFF/ON/OFF fault

right so its blinking 4 times twice, then when it reboots it blinks 3 times then 7 times

in standby I seem to lose the 24V off pin 1 and get 1.8v on pin 2

attached is the blink code info that I could find, any ideas anyone, im not familiar with the terms on the sheet, so is P-board is PSU and A-Board Main and also what is SU, SD, SC, SS-Board?

[R_J]

Re: Panasonic TX-40CX400B - 17IPS20 - DULLSCREEN+ON/OFF/ON/OFF fault

It may not use 5 volts for standby, it may use the 12 volts as standby? Standby must be working or you would not have a blinking led and any codes. The 24 volts will shut down in standby
I dont have that manual
NOTE: Those codes are for a PLASMA TV, This is an LCD tv correct?

[shepp]

Re: Panasonic TX-40CX400B - 17IPS20 - DULLSCREEN+ON/OFF/ON/OFF fault

ok thank you

[R_J]

Re: Panasonic TX-40CX400B - 17IPS20 - DULLSCREEN+ON/OFF/ON/OFF fault

Being that it is actually a Vestel produced tv I dought the Panasonic codes will apply

[shepp]

Re: Panasonic TX-40CX400B - 17IPS20 - DULLSCREEN+ON/OFF/ON/OFF fault

will any 17IPS20 PSU work or have I got to look to match the other number on the board?