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Old 09-02-2017, 12:32 PM   #1
FallinDeep
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Default Need help with my Samsung UN55JU7500 random "flickering" in the middle of the tv

Hello, I'm new to this forum to address my issue I've had with my tv for quite a while now and its getting very frustrating when it starts happening!
Im having like a flickering type of noise in the middle of my tv (horizontal) it happens randomly, mainly when alot of use is put into the tv at once, like if i play a game or watch a movie it happens more when the tv has been ON.

I've had the panel, and mainboard replaced by samsung... i am now out of warranty.. my options are limited the only thing they didn't replace was the PSU"PowerSupply" and I've done some research and there was 1 person on youtube that had same issue and mentioned PSU, but i don't know. id like to get more opinions! which is why i am here... all help would be appriciated..
also i don't know if interference can cause this as i have many electronics, including my router and modem on my one dresser where my tv hangs above.

thanks all,

kind regards.
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Old 03-21-2018, 11:26 PM   #2
Louis82
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Default Re: Need help with my Samsung UN55JU7500 random "flickering" in the middle of the tv

Hi there,
I'm working on repairing the power board for this TV UN55JU7100.
Power Board part number is BN44-00811A. I have found two diodes shorted but not sure how to order a replacement. Can you guys help me understanding this part number. I wrote it down as camera can't focus well on this smd diode.

Something like: ZH 0H (shows written vertically)
See pic
Attached Images
File Type: jpg image1.jpg (139.3 KB, 6 views)
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Old 03-21-2018, 11:31 PM   #3
Louis82
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Default Re: Need help with my Samsung UN55JU7500 random "flickering" in the middle of the tv

I found another shorted: ZG 0F

Thanks in advance!
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Old 03-22-2018, 05:17 AM   #4
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Default Re: Need help with my Samsung UN55JU7500 random "flickering" in the middle of the tv

this is a link to the smd code book it may help you find these
http://www.sphere.bc.ca/download/smd-codebook.pdf
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Old 03-22-2018, 05:53 AM   #5
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Default Re: Need help with my Samsung UN55JU7500 random "flickering" in the middle of the tv

Quote:
Originally Posted by FallinDeep View Post
Hello, I'm new to this forum to address my issue I've had with my tv for quite a while now and its getting very frustrating when it starts happening!
Im having like a flickering type of noise in the middle of my tv (horizontal) it happens randomly, mainly when alot of use is put into the tv at once, like if i play a game or watch a movie it happens more when the tv has been ON.

I've had the panel, and mainboard replaced by samsung... i am now out of warranty.. my options are limited the only thing they didn't replace was the PSU"PowerSupply" and I've done some research and there was 1 person on youtube that had same issue and mentioned PSU, but i don't know. id like to get more opinions! which is why i am here... all help would be appriciated..
also i don't know if interference can cause this as i have many electronics, including my router and modem on my one dresser where my tv hangs above.

thanks all,

kind regards.
Easy test, just unhook/turn off everything but the tv, to see if it's electronic interference.
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(Signature) One of the first and least expensive things you can do when you have an issue is take the powerboard out of the tv, flip it over and look the solder joints over with a magnifying glass if needed, add a little flux to make the solder flow well and add solder to any joints that look even a little suspect. You can practice on a scrap pcb board if needed, careful not to bridge any joints, and always let the board sit for quite a while or discharge the big caps with an appropriate resister before working on it (safety first) to try to keep from getting shocked, it doesn't take 1000 volts to KILL, a lot less can kill, so be careful, it's only a tv.
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Old 03-22-2018, 05:57 AM   #6
Andrew F. Ali
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Default Re: Need help with my Samsung UN55JU7500 random "flickering" in the middle of the tv

Quote:
Originally Posted by vinceroger69 View Post
this is a link to the smd code book it may help you find these
http://www.sphere.bc.ca/download/smd-codebook.pdf
Thanks....This is a very useful book to have.
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Old 03-22-2018, 06:08 AM   #7
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Default Re: Need help with my Samsung UN55JU7500 random "flickering" in the middle of the tv

Quote:
Originally Posted by Andrew F. Ali View Post
Thanks....This is a very useful book to have.
I also have this one if its any use
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File Type: pdf SMD-databook-2011.pdf (19.03 MB, 26 views)
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Old 03-22-2018, 06:14 AM   #8
Andrew F. Ali
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Default Re: Need help with my Samsung UN55JU7500 random "flickering" in the middle of the tv

Oh yes!!...This is really good...Thank you very much for sharing....
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Old 03-22-2018, 06:33 AM   #9
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Default Re: Need help with my Samsung UN55JU7500 random "flickering" in the middle of the tv

[QUOTE=Louis82;813721]Hi there,
I have found two diodes shorted but not sure how to order a replacement. Can you guys help me understanding this part number. I wrote it down as camera can't focus well on this smd diode.

Are you sure the diodes are shorted
The 2 legs at the bottom are common and will show a short , the diode is between the top pin and any of the bottom pins
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Old 03-22-2018, 09:44 AM   #10
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Default Re: Need help with my Samsung UN55JU7500 random "flickering" in the middle of the tv

Quote:
Originally Posted by Louis82 View Post
Hi there,
I'm working on repairing the power board for this TV UN55JU7100.
Power Board part number is BN44-00811A. I have found two diodes shorted but not sure how to order a replacement. Can you guys help me understanding this part number. I wrote it down as camera can't focus well on this smd diode.

Something like: ZH 0H (shows written vertically)
See pic
What is wrong with the power board? Pictures?
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Basic LCD TV and Monitor troubleshooting guides.
http://www.badcaps.net/forum/showthr...956#post305956

Voltage Regulator (LDO) testing:
http://www.badcaps.net/forum/showthr...999#post300999

Inverter testing using old CFL:
http://www.badcaps.net/forum/showthr...er+testing+cfl

Tear down pictures : Hit the ">" Show Albums and stories" on the left side
http://s807.photobucket.com/user/budm/library/

TV Factory reset codes listing:
http://www.badcaps.net/forum/showthread.php?t=24809
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Old 03-22-2018, 10:09 AM   #11
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Default Re: Need help with my Samsung UN55JU7500 random "flickering" in the middle of the tv

Thanks for the SMD Code Book gents - Still wondering if the numbers written vertically mean anything. I been going through my scrap boards and I have found ZH diodes but they also show 1F, 1H written vertically. Thoughts?

@chrismurphy - Yes, It test shorted from pin top vs any of the two bottom. I removed them from circuit board an they seems to be bad.

@budm - Blown AC fuse. Found 2 mosfet, a transistor-diode and 2 SMD resistors shorted. Replaced all, tried again and now transistor-diode blew again plus a resistor (which it was probably bad from the beginning and I just missed it at first), and the 2 ZH diodes.

I will post pictures by noon. Seriously the board is very cheap, like $25 on eBay, but I already spent a good time messing with this and I want to find the problem - Challenged.
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Old 03-22-2018, 10:19 AM   #12
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Default Re: Need help with my Samsung UN55JU7500 random "flickering" in the middle of the tv

So whcih section of the board where those parts are bad?
PFC, LED driver, main supply, standby supply?

http://www.shopjimmy.com/samsung-bn4...led-board.htm#
Pictures provided by shopjimmy.
Attached Images
File Type: jpg shopjimmy-bn44-00811a-top.jpg (835.3 KB, 6 views)
File Type: jpg shopjimmy-bn44-00811a-bottom.jpg (1.30 MB, 6 views)
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Old 03-22-2018, 10:32 AM   #13
Louis82
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Default Re: Need help with my Samsung UN55JU7500 random "flickering" in the middle of the tv

The blue dot is a 4.7 ohm that I found burned.
Red dots are the ZH and ZG diodes.
Yellow is a 10kohm resistir that test good but looked a little bit up so I removed it to replace it anyway.

Wonder if the DP807 diode I put in was bad (ordered from AliExpress) and it actually caused a worse mess.

As I said initially it was just the QP802, DP807, QP801 RP829, RP831 bad.
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Old 03-22-2018, 10:52 AM   #14
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Default Re: Need help with my Samsung UN55JU7500 random "flickering" in the middle of the tv

So you had problem in the PFC Voltage booster section, more likely the PFC IC got damaged when the PFC MOSFET went bad, I always replace the IC at the same time as the MOSFET since you can damage the new MOSFET if the IC is bad.
BTW, the part designator with 'P' indicates part related to PFC circuit: I.E. QP802

Last edited by budm; 03-22-2018 at 10:54 AM..
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Old 03-22-2018, 10:56 AM   #15
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Default Re: Need help with my Samsung UN55JU7500 random "flickering" in the middle of the tv

So you think the PFC IC is what it damaged my diodes. Because after I replaced the MOSFETs, I plugged in the board and the Mosfets remain doing fine, no short.
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Old 03-22-2018, 11:05 AM   #16
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Default Re: Need help with my Samsung UN55JU7500 random "flickering" in the middle of the tv

https://www.badcaps.net/forum/attach...6&d=1521736034
Those prts in that section are for the Gate drive circuits, they are connected between the Gate drive out of the IC and the Gate pin of the MOSFET, when MOSFET shorted out between Gate and Drain, that will dump 160VDC ~380VDC to the output of the IC via those parts so they blew up.
Look up the P/N of the PFC IC spec. sheet, it will have some reference circuit that shows you how it is being used.

Last edited by budm; 03-22-2018 at 11:07 AM..
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Old 03-22-2018, 04:07 PM   #17
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Default Re: Need help with my Samsung UN55JU7500 random "flickering" in the middle of the tv

I found NT811 cracked, replaced all burned parts except PFC Ic and still the same.
Last try will be the PFC IC but I canít tell the part number of it.
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Old 03-22-2018, 09:05 PM   #18
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Default Re: Need help with my Samsung UN55JU7500 random "flickering" in the middle of the tv

Replaced PFC IC SPC1012T and the same, diode location DP807C keeps blowing.
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Old 03-22-2018, 09:13 PM   #19
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Default Re: Need help with my Samsung UN55JU7500 random "flickering" in the middle of the tv

The two MOSFETs QP801, 802 did not blow?
Did you replace that Common Cathode DP807 with the exact same type and isolated case?
For that PFC Diode to blow, the Cathode must be seeing very low resistance to GND.
See the diagram showing how that diode being used in the dual PFC circuit.
Check the resistance between the two legs of the main filter cap CP810 or 814 to see what you get.
Attached Files
File Type: pdf Samsung Dual PFC CKT .pdf (53.4 KB, 10 views)

Last edited by budm; 03-22-2018 at 09:27 PM..
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Old 03-22-2018, 09:22 PM   #20
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Default Re: Need help with my Samsung UN55JU7500 random "flickering" in the middle of the tv

Correct, MOSFETS still measuring fine. Diode is shorted. Replaced with exact part number. Wonder if this Diodes are chinese fake components.
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