Thomson 55UA7706 LCD TV startup problem?

[budm]

Re: Thomson 55UA7706 LCD TV startup problem?

Thanks for the follow-up.

[SMPS]

Re: Thomson 55UA7706 LCD TV startup problem?

topic locked

Zener has a 18V value. If this zener breaks, then also FSFR1700 fails and need to be replaced, no empti place here! Although it may seem to work even without this zener it not work without a zener.
Now this TV works again.

[SMPS]

Re: Thomson 55UA7706 LCD TV startup problem?

Yes, this is weird but - I was measured this maybe tens of times and compared to others and this is clear that this zener is defective. I dont know why? Also, first time I have this fault but lets see when new IC is in place and also new zener.

I have now 17V, 18V and 24V SMD zeners too. I think that maybe I`ll try then 18V here?

[Diah]

Re: Thomson 55UA7706 LCD TV startup problem?

well till now i never faced Glass Ziner defect. buy any value glass ziner and compare the test with diode mode. LOL

[dick_barton]

Re: Thomson 55UA7706 LCD TV startup problem?

The data sheet for the IC says VAR (Autostart Reset Pin Input Voltage) = MAX VLcc
VLcc on the data sheet says maximum 25V

So it's possible that the zener may be somewhere around that value.

https://cdn.badcaps-static.com/pdfs/...04400a7892.pdf

[SMPS]

Re: Thomson 55UA7706 LCD TV startup problem?

I finally got new PSU chip and now is still only one problem - this damaged zener.

Like as I say some time ago, I was measured all components which located near this FSFR1700XSL chip and clear is that this D404 (some kind of zener) is damaged BUT - how can I be sure what value zener this must be?
I draw this part of PSU zircuit and measured all little SMD parts, this circuit is below and there is also componets values which I measured.

Now - how I can calculate this D404 value? Or rather what does this value depend on, on which should I proceed? There is no this kind of zener circuitry in FSFR1700XSL datasheet.
If I choose an incorrect zener - I am afraid thst this ends badly to new FSFR1700 chip?

Therefore - how I can choose correct value zener?

[budm]

Re: Thomson 55UA7706 LCD TV startup problem?

Your post #21:
"This 24V comes to inverter board from psu pin no. 10 (marked red). And yes, I have 22.92V before but after disconnect/reconnect this 14pin cable, I dont have this anymore, also, no standby."
Are you now saying you do not even has standby Voltage?

[SMPS]

Re: Thomson 55UA7706 LCD TV startup problem?

OK.
I once thought that I marked with a dot, not a comma... My country also have a comma for this kind of separation, but I get previously resented that I used a comma and tried to prevent now

Anyway I need to figure this zener value out now and new inverter or ICs. I drew a diagram but i will only get the component measuring device tomorrow or the day after tomorrow, so if i get it done maybe it will give some overview to find out the value of the suitable zener. OK, lets see

[Diah]

Re: Thomson 55UA7706 LCD TV startup problem?

aha... mV was easy to write 0.41 any way ..so now you have of sure zener defect and back light strings defect. i would say start first by replacing the BL and when you got the correct zener will be easy to you for further trouble shooting in case there were more issue

[SMPS]

Re: Thomson 55UA7706 LCD TV startup problem?

before we got lost.... lets follow yours POST
this is your first POST.

Look next answer

after i asked you to disconnect 24V socket and plug in again.. you wrote at POST No 8

Yes, I wrote this but there is +41.45mV , not 41.45V. There is over 1000x lower value this +56V rail.

the inverter turned on and the 56V exist but low 41.45V.
it mean you have LED back light issue or Inverter issue. that's all before you went to play at HOT AREA... BTW i think your measurement to the zener Diode wrong... you need with Ohm testing that read resistance at one direction only.

Then is only possible that inverter itself is bad, this OZ9998, all other semiconductors is good. And If you need I can take picture this zener measurements - virtually https://i.ytimg.com/vi/GwRyAGgpbPg/maxresdefault.jpg but I have 1000ohm resistor and adjustable supply, if I now get new THT zeners from manufacturer packaging I get good results - for example, same setting, 3.6V zener I get very close (to name value) results (if you need how close - how many I measure?), If I get 15V zener then I get also very close results, also 12V and this other zeners which located near FSFR1700XSL give me result 18.028V for example. This broken one gives me 0.0009V reading and 0 ohm (multimeter reading) but if this really helps, I can measure until to 0.001ohm resolution but - do this help?
continuity test/diode test gives me also short "peep" signal, both sides.

What DMM I using now? Fluke 110 and UNI-T UT139E, there is virtually no difference, only second show me 1 count more.

Once again, this very low +56 rail...this is only tens of millivolts - and this sends me from the beginning.

Today morning I re-measured again new LED strips and sure that new ones is good, all LEDs lit.
87.7V is one group voltage (18 LEDs).
If this helps also I can post picture my DIY tester (circuit is here: https://www.drive2.ru/c/513423827611419614/ ) but if this LED lit then there is no errors. Old LED stripes which located at this moment inside a panel, they are definitely broken because they lit very weakly.


E: maybe my writing skill barrier is really high but I mean milli-Volts at there 41.45milli-Volts, not Volts

[Diah]

Re: Thomson 55UA7706 LCD TV startup problem?

before we got lost.... lets follow yours POST
this is your first POST.

Inverter board can get from the main power supply as follow voltages:

+24V (I have there +22.66V)
+56V (I have 0 (zero)V)

after i asked you to disconnect 24V socket and plug in again.. you wrote at POST No 8

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

so the inverter turned on and the 56V exist but low 41.45V.
it mean you have LED back light issue or Inverter issue. that's all before you went to play at HOT AREA... BTW i think your measurement to the zener Diode wrong... you need with Ohm testing that read resistance at one direction only.

[SMPS]

Re: Thomson 55UA7706 LCD TV startup problem?

1) The pictures of the boards are very poor, I cannot read the pin label (the oin names are printed on the bottom side of the board) of the connector of the power supply board that goes to the LED driver board.

Yes, below is new, do they help?

2) Were you getting 24V to the LED driver board? And now you don't since you start playing with FSFR1700XSL and D404?

This 24V comes to inverter board from psu pin no. 10 (marked red). And yes, I have 22.92V before but after disconnect/reconnect this 14pin cable, I dont have this anymore, also, no standby.

3) The 24VDC is generated by FSFR1700XSL so the circuit was working. I do not understand why you start messing with the FSFR1700XSL.

Because (also question 4) ) one technician suggested to measure C401 22uF/50V voltage and there is 1.6V, they told that I must check this part of circuit, I then measure this SMD components and find this zener conducted both ways, soldered it off and checked with a zener tester - same result, 0.0009V zener voltage.

4) As you can see that D404 is connected in parallel with resistor. So when you check D404 off the board, does it show conduction and low resistance (<10 Ohms) in both directions.

See previous.

5) Right now you need to get the FSFR1700XSL working again before going back to troubleshooting the backlights issue, or just buy a new power supply board assembly that match the number on the barcode sticker, not the blank PCB part number..

I dont know this zener real name value - if I order new FSFR1700XSL and if there is this broken zener...i dont think that this new IC helps, they also fail probably.

6) Where is the pin that is supposed to have 56V?

In inverter board, pin 11 to 14 is marked 56V, in PSU, pins 12 to 14 is marked as 60/120V, 11 is not connected (see 1. (PSU connector) and 4./5. picture (inverter connector).
Pictures 2 and 3 is LED stripe connectors from inverter board.

Last 2 pictures is PSU FSFR1700XSL circuit top and bottom view

[budm]

Re: Thomson 55UA7706 LCD TV startup problem?

1) The pictures of the boards are very poor, I cannot read the pin label (the oin names are printed on the bottom side of the board) of the connector of the power supply board that goes to the LED driver board.

2) Were you getting 24V to the LED driver board? And now you don't since you start playing with FSFR1700XSL and D404?

3) The 24VDC is generated by FSFR1700XSL so the circuit was working. I do not understand why you start messing with the FSFR1700XSL.

4) As you can see that D404 is connected in parallel with resistor. So when you check D404 off the board, does it show conduction and low resistance (<10 Ohms) in both directions.

5) Right now you need to get the FSFR1700XSL working again before going back to troubleshooting the backlights issue, or just buy a new power supply board assembly that match the number on the barcode sticker, not the blank PCB part number..

6) Where is the pin that is supposed to have 56V?

[SMPS]

Re: Thomson 55UA7706 LCD TV startup problem?

I think that this maybe is also not good but I have night and my phone cam is not good to make better pictures.

And if I want take a picture to whole pcb, i cant take it very close
There is limit also if I take many shots closer and put them together.



And LED is this: https://www.aliexpress.com/i/33023939915.html

If I search from google all this PCBs (all markings which there is) then I only get different e-store etc, no topics, no information which I need. Some chinese page but maybe tomorrow I try chinese pages.
At this moment there is probably not much to do - I dont know what is this D404 zener value - if I order new FSFR1700 chip I dont know anyway which zener there MUST be - I am 99.9% sure that this is not broken if this TV shipped out to factory, but maybe because I try different zeners today its also my fault now and maybe this IC is also broken because I connect one times more TV to mains and there is now only short standby flash.
Maybe now is really time to throw it away or only new PSU because (this service manual searching led me trought multiple manuals) all TV PSUs nowaday seems very bullshit - tens of different "failsafe" circuits which fail first itself... for why?
At this moment I dont really know anymore - maybe this fault is now gone further now because there is not a way to sort it out - sure that I have very little change to get this model PCBs at my country..
Need to order and even then there is 50/50 change. This psu IC also - I can order it but if there is "failsafe" which lets smoke out this IC to protect this "failsafe" circuitry - what is the point to order and solder. I dont really understand - broken zeners, weird voltages...I have to repair some time ago much valuable PA amps and there is no this kind of "failsafe" things, I was made this year some IR2153, IR2161, IR2156 based smps to my DIYbuilt amplifiers and there is not this kind of "failsafe" there is no problem also if user know what they do...TVs and their "systems"...i dont have a words more

[budm]

Re: Thomson 55UA7706 LCD TV startup problem?

1) Show us where the '56V' pin you are talking about.

2) Can I get good clear straight shots pictures of the whole top and bottom side of the power supply board? Right now your pictures are not clear enough for me to clearly read any prints on the board.

[SMPS]

Re: Thomson 55UA7706 LCD TV startup problem?

OK.
Moment ago I did it - disconnect this black cable to inverter board and connect it back, there is no standby anymore after connecting back.
If I reconnect TV to mains there is only one very short blink in this standby - maybe because I try to replace this zeners today earlier.

Yes, there is no image and yes, i did not connect anything to input (HDMI or nothing) - maybe this is why not sound or nothing.

I have tester to test LEDs, they give me very weak light and I have also new stripes I connect this stripes and they dont give me any light if connected (they are new, also tested before and now too, they are OK (also now), gives me very bright light if connected to tester. Because I have DIY built tester I have 170V open circuit Voltage and if I test this stripe, one string (18 LEDs) gives me 87.7V. Sure that old stripes is broken because they are very weak, only darker room I see some light. And this 56V thing - some technician say that there must be this voltage - maybe they are wrong because they dont have also any service manual. But this 24V goes trought one wire and near the connector there is 2 series connected 47ohm 1206 resistors and this pcb track is also very thin compared to 56V traces and 3 wire. After this resistors 24V goes to 2SD1664 collector, this transistor is also low current - 144 LEDs to drive???

Maybe this original stripes is not broken and really there is some serious problem - I get this TV from friend, there is no money spent of that (only new LED stripe). Friend told me that if I want to tear it to parts then they give this TV to me. I was wondering if I could get it to work...this is not old, 2-3 years used.
OK, now I have more problems here and I think that if I find new PSU I can try this T-CON disconnecting.

If this fault now arise, there is no fire, no smoke, what went broken - there is now big question, maybe now this zener part...

In physical screen itself is good, there is no scratches or other physical marks. How often do panels itself fails electrically at all? If we take 1000 panels how many fail say second years when they are use? some orders of magnitude?

And yes, bad thing is that 3D model - people speak that this 3D is not very good, I have also one Philips 3D which fail after quarantee.
This Thomson is 55 inch, 4K (UHD).
I learn that Thomson and seems like TCL too is brands which I never buy - no manuals or nothing.
I have LG 42 FullHD and 6 years there is no any problems, before I have Samsung CRT...12 years or so - no any problems..
But seems like this good old days is ended and newer models is not that good like older.

OK, maybe some day I try if I find new psu or service manual.

-----------------------------------------------------------------------------------------------

But this zener mystery is haunting. I treated this psu before this measurements like any other high Voltage boards, there is no change that this zener fails if I disassemble this board, measured this broken zener after filter capacitors are empty (there is no resistor and 10-15 min to wait until they are not energyzed), if continuity gives me short, I soldered this zener out and measured Zener voltage - i get 0.0009V (measured at 25V test Voltage). This is mystery - why this broken component is in this board? This is really fist time when I see this kind of "planned obsolescense" thing..need to tear appart some newer PA amp, maybe I find this kind of "faults" more..

[Diah]

Re: Thomson 55UA7706 LCD TV startup problem?

if you are waiting on explanation on any test suggestion over here.. then we will wrote books..lol
take it easy..
most 3D TV set such Toshiba too HD or UHD, the Led back light will have an extra inverter boards and it work with feeding of 24V from power boards like yours.

unplug and plug in the 24V socket while the TV on. it will switch the inverter to be ON in case if its shutting off because of fault led at back light strips.

you said you cant see any picture on screen.. did you put signal... can you hear sound ?
this why we want to be sure the T-CON had 12V on F1.

remove one ribbon.. its test if the panel had fault or short so there are SOS signal go back to the main boards and it shut down the back light..

i don't know what are you talking about 56V... where should be? on LED strips socket?
if so then it will make no sense at all.. take out your screen apart and test you back light or by buy LED tester to be sure the back light all working.... still this make no sense again.. because you said there are no picture on screen with torch ..!!!!

[SMPS]

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

---HOW it is possible if I disconnect socket where is also this low level signals? (where there was an explanation?) What picture I see then? If there is blank screen - do i need to connect something? No, there is NO any picture if I watch torchlight, I say it - i also feel like a buggy that i have to do things over and over again that i've already done it.
This cable is wery strongly in connectors - i can say that I haven't encountered ribbon cables so hard before and that's why I suspect they can't be caught in the socket (yes, I lifted the lock ... [because it's probably thought I haven't seen any electronic devices in my life]).
I can pull it open and see, what happen but whrere we are then? Same point because - no explanation. You ask whether F1 is OK, even you mention that there must be same readings at both sides - HERE i read like ...why i didn't read the suggestion that i can also do a continuity test...because I have done this tens of times (no tv but audio devices) and I would have mentioned at this if, for example, this fuse would be broken because it would have seemed bad taste right away..but it is OK - what next? (no explanation - OK, if this fuse is broken, T-CON is unrepairable, I quess? - no explanation, or...I cant see)

MAN.. we are all willing to help you and any other posted issue over here..
but you are following your head ONLY..

yours power boards was working.. why you go to the HOT area and damage it.. did any one here write to check any component at HOT AREA ??

for me i hate to keep writing and suggest and OP just follow his head and brain. here we are... you are at lost.

Yes, this board working also now (like they work before) - but also, what explains this zener D404 which is broken, if I replace this for 18V on standby doesnt come on, if i replace this for 2x3.6V items, also standby does not come on but if I place this broken (0.0009V zener reading and continuity test, shorted) zener place - woilaa - standby come on.
BUT this is pointless if there is not this 56V rail. Yea, I can pull these T-CON wires open but the inside feeling says that it does not change anything.

Can I get help from oscilloscope (I have this too), I have Fluke, newer UNI-T 5 digit meters and soldering stations, so-all this which i need to do audio things but I have no experiences this TV bullshitlike (just my thoughts) error prone power systems - I have lot of experiences raw-SMPS (some hundreds to 2-3kW O/P and to +-170V voltages at rails - there is all simple, huge input rectification stage, raw smps control circuit, H or F power stage, huge transformer, secondary rectification [for PA-AMP]), but i have no TV experiences - I ask only help, not bullying (that this stillness if I found this broken zener... if there is no any problem - who forbids to say it..nobody)

If we speak to hate or hating...I hate also many things, one is bullying

[Diah]

Re: Thomson 55UA7706 LCD TV startup problem?

Want to EDIT last post but I cant

bye

MAN.. we are all willing to help you and any other posted issue over here..
but you are following your head ONLY..

yours power boards was working.. why you go to the HOT area and damage it.. did any one here write to check any component at HOT AREA ??

for me i hate to keep writing and suggest and OP just follow his head and brain. here we are... you are at lost.

[nomoresonys]

Re: Thomson 55UA7706 LCD TV startup problem?

Get the same zener and replace it, get a couple, maybe test the components around that zener to make sure they are ok before replacing, did you follow Diah's instructions? Don't give up, youtube is your friend, there is hardly a problem that many people haven't already encountered and solved, good luck, hope you save it.