Thomson 55UA7706 LCD TV startup problem?

[SMPS]

Re: Thomson 55UA7706 LCD TV startup problem?

Want to EDIT last post but I cant

OK, last post here - no help and seems like there are not even like-minded people

Anyway, replaced this broken zener with 18V THT component but no change.
If before red standby light came on then now it stays off - broken zener=standby, new zener=no standby and no power.

I cant any information nor google, nor yandex, nor other search engine - why this zener is here? what they do here? What happen if they are too high or too low values or what happen if you leave it out at all? I cant get any information - from FSFR1700 datasheet there also not either even a little similar reference design...

There is not problem this 24V node, nevermind - this TV LED driver need 56V to feed LED stripe, there is 18 LED in one string, there is 4 strings in one stripe, one string need 56V to came on, no 24V , no, this 24V pcb track is maybe 0.5mm wide and there is no change that this current which 144 LED needs can get through this trace.
And this +24V is close enough +22,9V but - can't forget that there must be +56V, much higher current than this 24V and there is very little voltage at this +56V node, this is much biggewr problem I think...but OK, seems like there is no help anyway, some ask picture but no any words afterthat...hope that this "TV-inside picture collection" gives something interesting.

bye

[SMPS]

Re: Thomson 55UA7706 LCD TV startup problem?

Nobody

I searched with different methods to maybe find some circuit diagram or fragment but nothing, in this PSU board is printed also: 40-E461CD-PWD1XG

But google says - no circuit diagram or even fragment this FSFR1700XSL part.
There is multiple PSUs which use same IC but all are little different - and I dont know what zener I can use to replace this D404 (measured, shorted) - there is also D402 and D403 and they are both 18V zeners (measured).

What happen if I connect this D404 place for example 9.1V zener or 12V (i dont have this 18V at this moment and local store does not sell SMDs).
Or can I just series connect two 9.1V one and just try? But if there must be some other (higher/lower) zener value, what is the result?
Most closest circuit I find is 40-E421C6-PWB1XG, there is weird note thereat D404: 79C18V (bzx79c18V?) but why - other zener is marked just 18V, why this exact D404 is marked like recomended model?

[SMPS]

Re: Thomson 55UA7706 LCD TV startup problem?

OK.
Haven't tried it yet but main PSU contains a FSFR1700XLS resonant converter switch https://cdn.badcaps-static.com/pdfs/...f141f56ce1.pdf

Found that there is one zener diode in this circuit part which is shorted, it is not exact circuit like Philco PH48S61DG (service manual page 14) but there may be some reference, this part of this main PSU produces LED driver +56V which I dont have. Hope that this FSFR1700XLS itself is good but I cant see any marking in this shorted zener (D 404 in picture) body, only blue band - what it is?

[Diah]

Re: Thomson 55UA7706 LCD TV startup problem?

no need any relay ..
its save if you unplug the socket of 24V between PWB and LED converter boards.
so keep the socket unplugged.. and measure the 24V to see it come high to 24 or remain 22.92V.

by the way you should hear sound and can see picture on panel with torch ... if no sound or picture.. you can put back the socket of 24V in place.. and just disconnect the panel from T-CON ( just unplug the 2 ribbon cable from T-CON side) and turn on the TV ..check the back light come on or not

[SMPS]

Re: Thomson 55UA7706 LCD TV startup problem?

Sorry for delay.

Image from rear side, at below.

Quick measurement from T-CON fuse shows that this fuse is in good conditions (continuity test).
I haven't done this 24V circuit test yet but I will soon. How long can i turn on the tv without this 24V node? Can it damage the power supply if there is no load in this node longer time?
If I connect a relay between this 24V wire and turn on the relay (from aux power) a few seconds after turning on the TV, will it not damage the power supply itself?
Also, in a moment I can measure this P-DIM. When I get the result, I note here.



EDIT

Results are:

P_DIM +0.430V
Fuse F1 from T-CON, +11,988V (both sides)


Measured at inverter board IN DC MODE:
+56V pins: measured +41.45mV it is not very stable also - here seems something wrong ????????????
+24V pin: measured +22.92V (little low but not very?)
PT pin: measured +0.55mV
BL_ON: measured +3.109V (little low?)
P_DIM: measured +0.4316V
3D_EN: measured +0.62mV

[budm]

Re: Thomson 55UA7706 LCD TV startup problem?

1) Show us the pictures of the whole backside of the TV so we can see how all the boards are connected together.

2) What Voltage do you get on P-DIM?

[Diah]

Re: Thomson 55UA7706 LCD TV startup problem?

You mean this in red circle?

yes this is the F1 fuse. put yours voltmeter black probe on chassis and the red one on each side of it and check do you have 12V.?

[SMPS]

Re: Thomson 55UA7706 LCD TV startup problem?

You mean this in red circle?

[Diah]

Re: Thomson 55UA7706 LCD TV startup problem?

Here it is.

This is inverter board.
I try this method but can you tell me - what is the purpose of this 24V node? 56V seems backlight power (72 LED in one strip, 4 groups 18 LED per group) but for what is this 24V purpose?

EDIT: No image if I illuminate the screen from different angles with a flashlight, I forgot this to mention in the first post.

24V this the led voltage which it converted to high at led converter boards.

you wrote you have 3,3 on BL on.. so i assume the main boards working and send signal power on and bl on..
if there is no image on screen.. you need now to check if you have 12V on the T-CON .. it had fuse on it you need to check both side of the F1
if you have 12V

[SMPS]

Re: Thomson 55UA7706 LCD TV startup problem?

Here it is.

This is inverter board.
I try this method but can you tell me - what is the purpose of this 24V node? 56V seems backlight power (72 LED in one strip, 4 groups 18 LED per group) but for what is this 24V purpose?

EDIT: No image if I illuminate the screen from different angles with a flashlight, I forgot this to mention in the first post.

[Diah]

Re: Thomson 55UA7706 LCD TV startup problem?

first please upload photos over here on yours LED driver boards
use Flash light ( torch ) to see if the screen show any image at dark room...
in case yes you can see some things on the screen.. then while the TV ON. unplug the socket (24V) between power boards and led driver boards and plug it in again fast...see if yours back light flashing on or not.

[SMPS]

Hello.
My first post here.
I apologize for the typos because English is not my native and I haven't learned English in my school years. I have tried to learn it myself but probably I still make many of mistakes because reading written language and trying to communicate are two different things..OK, hope that these mistakes are forgiven

My concern is as follows:

I need help finding a service manual for Thomson 55UA7706 tv. Or - which may be the cause when the TV is in standby mode and the screen stays blank when you try to turn it on (even no backlight flash), I`ll connect new strips but I cant get 56V from BL inverter, there is two chips OZ9998HEGN in this inverter, they seems fine. Inverter board can get from the main power supply as follow voltages:

+24V (I have there +22.66V)
+56V (I have 0 (zero)V)
there is also
3D_EN pin (i think some logic pin?)
P_DIM (dimming I quess?)
PT (I dont know what it is?)
BL_ON I have there +3.06V (backlight ON? logic signal?)

Backlight driver module is: 40-RA6080-DRA2LG
Power supply board is: 81-PE461ED-PL200AA
Motherboard is: 40-NT67HC-MAD4HG
T-CON/ Logic is: ST4851D01-4-C-2
LCD panel is: LVU550SE4L 55E6700-LPE002A

Where else should I look or measure?
Thanks!