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Shahid
Shahid, Technician
Category: TV
Satisfied Customers: 9465
Experience:  I have been repairing electronic gear since 1993 as a qualified Sony tech
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Model LTJ550HJ05-C. Blinking power light, no picture, no

Customer Question

Model LTJ550HJ05-C. Blinking power light, no picture, no sound. Have replaced all three boards (PS twice), disconnected IR control cable. PS low voltage supplies turn on and off, HV ok. What is problem? John
Submitted: 5 months ago.
Category: TV
Expert:  Shahid replied 5 months ago.

Hello and Welcome. My name is ***** ***** I'll assist you today. I'm sorry you're having trouble with it. I need additional info to troubleshoot the issue.

1- Could you please get me the complete model number written on back of TV?

2- What are the three boards you replaced in TV, please intimate name/ part number of those boards?

3- Is there any change in TV symptoms with new boards?

Thanks.

Customer: replied 5 months ago.
1. model code: UN55D6000SFXZA, VER: H302
2. Main board BN94-05038D, Power supply board BN44-00424A, TCon board BN96-16491A (BN95-00498B)
3. Symptoms did not change, that is low voltages still turned on and off and power LED blinked.
Expert:  Shahid replied 5 months ago.

Thanks for the info, working on it and get back to you in 10 minutes, is this OK?

Customer: replied 5 months ago.
Symptoms are the same with LED connector connected or not.
Customer: replied 5 months ago.
10 minutes if ok.
Customer: replied 5 months ago.
Working at home...going upstairs for lunch, ok.
Expert:  Shahid replied 5 months ago.

Please disconnect CNL802 connector of power supply board, this connector harness goes into screen for backlight, turn On the TV to see if it stays On now?

If not, disconnect CNL803 connector of power board that goes to main board, and check STBY (standby) volt with meter, are they stable/ constant?

Please reply back with the result.

Thanks.

Customer: replied 5 months ago.
I am back.
Expert:  Shahid replied 5 months ago.

Welcome, did you get my previous reply?

Expert:  Shahid replied 5 months ago.

If not yet, let me repost it here....

Please disconnect CNL802 connector of power supply board, this connector harness goes into screen for backlight, turn On the TV to see if it stays On now?

If not, disconnect CNL803 connector of power board that goes to main board, and check STBY (standby) volt with meter, are they stable/ constant?

Please reply back with the result.

Thanks.

Customer: replied 5 months ago.
CNL802 disconnected...low ps going 0 to 5.3 vdc
CNL803 disconnected...low ps going 0 to 3 or 4 vdc.
Expert:  Shahid replied 5 months ago.

Can you elaborate low ps?

can you find STBY pin of CNL803 and check 5V there?

Customer: replied 5 months ago.
I have tried that before and after new boards.
Expert:  Shahid replied 5 months ago.

While CNL803 disconnected, you will only get standby STBY volts on that connector.

Customer: replied 5 months ago.
The screened chart doesn't list STBY...only +5 at 35 ma and +5 at 3.5A
Customer: replied 5 months ago.
What capacitor pins?
Expert:  Shahid replied 5 months ago.

Please check attached image of power board where connector pin configuration table is marked with red arrow.

Customer: replied 5 months ago.
Pin 15 (arrow) is bouncing 0 vdc to about +4.98 vdc.
Expert:  Shahid replied 5 months ago.

This is odd, volts bouncing even both connectors are off of power board and only AC power cord is plugged in?

Customer: replied 5 months ago.
Correct. However, some switching power supplies may not function correctly, if UNLOADED.
Expert:  Shahid replied 5 months ago.

I agree, but standby section of this type of PS board does work even no load connected.

Do you have some kind of load to connect to 5V DC output (across pin-15 and GND pin) of power board to verify it?

I mean 6V bulb, small DC motor or 6V LED etc just to verify if it still bouncing?

Customer: replied 5 months ago.
Could you please send me the power supply board schematic?
Expert:  Shahid replied 5 months ago.

Let me check if service manual contains schematics of PS section, hold on please.

Expert:  Shahid replied 5 months ago.

I'm afraid, service manual doesn't have any schematics at all, do you need the copy?

Also try the load suggestion I mentioned in previous reply..

Do you have some kind of load to connect to 5V DC output (across pin-15 and GND pin) of power board to verify it?
I mean 6V bulb, small DC motor or 6V LED etc just to verify if it still bouncing?

Customer: replied 5 months ago.
I have the manual. Tried a motor load...just turns on and off with the 5 vdc.
Expert:  Shahid replied 5 months ago.

OK, now it is confirmed that power supply board is defective, standby volts must stay constant when plug power cord in as this volt supply boot up the main board that will turn On rest of voltage supplies. Please swap the power supply board to resolve the problem.

I trust my input will help you out. Please feel free to respond if you have any additional questions.
A positive rating to answer would be greatly appreciated, please click on 5 star on this page then click submit/finish button so I can get credit on website for my work. If you don't see rating option then intimate here.
Regards,
Shahid.

Customer: replied 5 months ago.
Don't agree. Have replaced PS board 2 times, as stated earlier.
Expert:  Shahid replied 5 months ago.

Let me explain, we have isolated the Power Supply board now and standby volts is the only output that you can get it from which should be stable/ constant, is this correct and do you agree?

Expert:  Shahid replied 5 months ago.

Have you checked pin-14 (A5V) output of power board?

Customer: replied 5 months ago.
No. I can't agree. I have replaced the power supply board twice...new boards from two sources. I still feel another low voltage needs loaded...there is still +5 and 35 ma, 12.8vdc and 3A and 18vdc ant 0.35A. Is it possible the LED backlight is OPEN. and is the missing load? What is the backlight supply?
Expert:  Shahid replied 5 months ago.

Backlight supply would be approx 150V (it varies due to screen size, number of LEDs inside screen).

If power board is disconnected (say it is out of TV) and plug the AC power cord in it and hook it to wall outlet, PS board should provide standby 5V output that should be stable.

There are two 5V outputs on this PS board, one is B5V and other is A5V.

Have you checked both output volts?

Expert:  Shahid replied 5 months ago.

Just to add more info, one of 5V output is switched, meaning it will turn On when power board get PS-ON command from main board.

Customer: replied 5 months ago.
There is a constant +5.3 vdc at CS851 and CS852. BUT that traces to pin 15, which is jumping zero to +5.3vdc. NOw I'm going crazy.
Customer: replied 5 months ago.
Sorry...it doesn't trace to pin 15. Cannot see yet where it goes, except to QS851.
Expert:  Shahid replied 5 months ago.

If you look at connector, pin-14 is marked as A5V and pin-15 is for B5V, correct?
Do you get a5V stable or bouncing?

Customer: replied 5 months ago.
The stable +5 vdc goes to pin 14. It is the 35 ma 5 vdc. Wouldn't that be the STBY +5??????? All the other low voltage supplies +5, +12, and +18 are jumping to zero. I am going to find a way to look at pin 16, which is the on off command.
Expert:  Shahid replied 5 months ago.

OK, if pin-16 is high, jump it to Ground, if pin-16 is low then jump it to 5V, this will turn On the rest of voltage on power supply board.

Expert:  Shahid replied 5 months ago.

pin-14 5V are stable that means standby section is working, this what I'm trying to explain.

Customer: replied 5 months ago.
Hi Shahid, pls opt out. I would love to hear what other expert would suggest. I already changed the power supply board twice, I dont think that's the problem. My tv isn't working still. Thanks.
Expert:  Shahid replied 5 months ago.

OK, opting out.

Thanks.

Customer: replied 5 months ago.
Made some more measurements...all voltages turn on and off (except standby +5) for the on off control line. When on, they all jump zero to their voltage, except the standby......nothing connected except AC power.