2 seconds then black: Proscan LED TV(PLED5529A-C)

[good_ol_Wes]

Here is the problem:

I am able to turn on my Proscan LED TV, the power LED turns blue(meaning it is on) and an image of the Logo appears. Quickly after the screen goes black(about 1-2 seconds). I have not tried playing sound through it. I have put the screen in a dark room and have tried the flashlight test on it and I was able to see and navigate around the menu when the light was shined at a specific angle. I have done some research on what the problem could be and I believe that I need to replace the T-Con/LED Driver board. I believe this because the LED's illuminate for a second or two then turn off, so I dont believe there are any broken or burnt out LED on any of the strips. another thing that points to the driver board being the culprit is that the TV passed the flashlight test and was showing an image on the screen that wasnt illuminated/bright enough to see (meaning that the logic and power boards are operating correctly i think). what i am worried about is that the LED driver board is working correctly and causing the strips to shutdown as a safety because of a short or bad LED. Is there any way that I can be certain where the problem lies?

I also have a decent amount of tools and knowledge on electronics and circuit repair. if you need me to take voltage levels, i can.

TV Info:
Proscan 55" LED ATSC Tuner
Model: PLED5529A-C
Model #: CN55CM823
S/N: A1408120370000722

[CapLeaker]

Re: 2 seconds then black: Proscan LED TV(PLED5529A-C)

Measure the voltage for each LED string on the connector. That will tell you if you got a bad LED in there.

[good_ol_Wes]

Re: 2 seconds then black: Proscan LED TV(PLED5529A-C)

I am having a hard time determining which connector you are talking about? is it the two ribbon cables leading from the T-Con board? Can you reference somewhere on the pictures i posted and I will be happy to measure and post voltages

[attainteddragon]

Re: 2 seconds then black: Proscan LED TV(PLED5529A-C)

these are your connectors for your backlight led's.
measure each pin with reference to ground and record what the voltage goes up to when you power the set on and what the voltage settles at, then disconnect the connectors and remeasure the voltage at the pins on the ps in the same manner.

[good_ol_Wes]

Re: 2 seconds then black: Proscan LED TV(PLED5529A-C)

i took 3 measurements of each side(left and right) with and without the connector attached.

with connector attached:
left side -
off: black- 0.612 , red- 0.00
start up: black- **** , red- 0.00
on: black- 0.601 , red- 0.00

Right side-
off: black- 0.605 , red- 0.00
start: black- **** , red- 0.00
on: black- 0.591 , red- 0.00

Without connector (3 prongs):
left side:
off: left- 0.60 , middle- 0.60 , right- 0.00
start: left- *** , middle- *** , right- 0.00
on: left- 0.59 , middle- 0.59 , right- 0.00

right side:
off: left- 0.59 , middle- 0.59 , right- 0.00
start: left- *** , middle- *** , right- 0.00
on: left- 0.59 , middle- 0.59 , right- 0.00

**** - this means that during the start up procedure the voltage jumped, then was unreadable/caused the multimeter to reset, then returned back to normal at 0.60 volts.

[good_ol_Wes]

Re: 2 seconds then black: Proscan LED TV(PLED5529A-C)

looks like to power coming to the connectors, but how do the backlight LED's illuminate during the startup (before turning off) without allowing me to measure a current at the connectors? Does this mean that either there is a bad LED?

[attainteddragon]

Re: 2 seconds then black: Proscan LED TV(PLED5529A-C)

since your backlights do come on, there is voltage on the red wire. set your meter to 200v and retest.

[good_ol_Wes]

Re: 2 seconds then black: Proscan LED TV(PLED5529A-C)

it still doesnt measure a current going through the red wire at any part of the process. with the black wire it drops to -1.00, then jumps up to around 50v, then 12-18v, then back down to 0.60v. It seems to me that the black wire is the live wire and red is ground since it doesnt measure any voltage, but black does.

[CapLeaker]

Re: 2 seconds then black: Proscan LED TV(PLED5529A-C)

**** - this means that during the start up procedure the voltage jumped, then was unreadable/caused the multimeter to reset, then returned back to normal at 0.60 volts.

Well this is the important part. Maybe use a DMM with Min/Max feature. Works like a charm. Compare the voltages between the strings. I put my money on a bad LED.

[good_ol_Wes]

Re: 2 seconds then black: Proscan LED TV(PLED5529A-C)

OK I will take those measurements tonight. After talking with a couple electrical engineers i work with and describing the problem and the voltage readings i got, they suggested that it possibly sounded like a capacitor problem. They also suggested that i measure the resistance of the LED circuit and that if there is no resistance then that will indicate a broken LED. Do you think these could possibly be the issues? if so, how would i be able to go about figuring out which capacitor went bad? or how can I test to make sure that it is indeed a bad LED and not the board controlling the LED's? Also is there a way i can do an LED strip test with taking apart the TV and screen?

[CapLeaker]

Re: 2 seconds then black: Proscan LED TV(PLED5529A-C)

Also is there a way i can do an LED strip test with taking apart the TV and screen?

Well, this is what I am trying to get you to do. Measure the DC voltage on each LED string. In your case there are 2 strings. The LED strips are current controlled. So if something isn't right, the PSU will shut it off (because the current drawn isn't right) and do exactly that what you are experiencing.

Now as for the caps: There are like just 2 of them. They aren't bulging, there is no leaks, the wrapping isn't shrunk (due to high ESR creating more heat), so I am not too worried about that at this point.

A resistance or voltage drop test of a DMM is worthless in a LED TV. The LED string is like christmas lights. LEDs can fail open or short.

[microvibe]

Re: 2 seconds then black: Proscan LED TV(PLED5529A-C)

It's almost always bad led in these I have 2 that frustrated me . I swapped parts on power board to point I did something wrong now I can't get more then 175 volts across the big cap. I ordered a new psu replaced bad led in both now both work. Now just need to figure out how to repair the broken psu.

So just bite the bullet open it up test the leds I use budm method just remove old one place new on top solder in wires .

[reydelcamino]

Re: 2 seconds then black: Proscan LED TV(PLED5529A-C)

one bad led and shuts it ( i fixd mine like that). No info at all at the time i did it, mine its a craig tv which is the same as proscan circuit.

[reydelcamino]

Re: 2 seconds then black: Proscan LED TV(PLED5529A-C)

if that doesn't fix it i have a craig power circuit board and a craig busted t-con to sell cheap (i dont need them any more).

[good_ol_Wes]

Re: 2 seconds then black: Proscan LED TV(PLED5529A-C)

OK so I went and took the rest of the TV apart to get to the LED backlight strips. I kept it plugged in and turned it on, and only the top half (3/6) LED strips illuminated. so i went and individually checked each LED on the backlight strips of the bottom 3 that did not illuminate. out of all the LED's on all 3 strips, there was 1 single one that was burnt out. So it looks like you guys were correct. will get my hands on a new LED or replacement strip and install it. that should do the trick right?

[CapLeaker]

Re: 2 seconds then black: Proscan LED TV(PLED5529A-C)

Yep!

[reydelcamino]

Re: 2 seconds then black: Proscan LED TV(PLED5529A-C)

i didnt buy led strip it was like 2X bucks, i decided to bypass it and cant notice the difference, just remove and jump it, i placed 2 diodes in series i know its not the same as an led but at least takes 1.4 v drop.

[CapLeaker]

Re: 2 seconds then black: Proscan LED TV(PLED5529A-C)

should have taken at least a zener...