Proscan 50" PLDED5066A-E no backlights

[budm]

Re: Proscan 50" PLDED5066A-E no backlights

I have no idea, I upload the spec sheet but it does not have application sample circuits to show how it is used. Need to locate application notes, will have to do more searching for it.
BTW, remove the LED female connector from the board and then check each pin of the female connector against chassis GND to see if any one of them show resistance or not.

[mnpdreed]

Re: Proscan 50" PLDED5066A-E no backlights

All of the wires of the female connector to chassis ground were OL

[budm]

Re: Proscan 50" PLDED5066A-E no backlights

OK, I want to be sure about this Voltage measurement I asked on post 41:
'What DCV do you have between the two legs of the brown cap C8F, and between the two legs of brown cap C9F?' and you report the reading of 0.661V between the two legs of C9F.
What I forget to ask you to do is to leave the probes on the legs of the cap, plug the TV into the outlet and then turn the TV on to see if you see the Voltage jumps up on the meter (set the meter to 200vdc scale) or not.

[mnpdreed]

Re: Proscan 50" PLDED5066A-E no backlights

C9F=.661
C8F=.669

I only have a DMM but I took pic of the screen with a high speed camera on my phone while turning on. The voltage when turned on jumps to 1.8 volts them drops to .66 volts.

[CapLeaker]

Re: Proscan 50" PLDED5066A-E no backlights

That's where the min /max setting on the DMM comes in handy.

[paulstef]

Re: Proscan 50" PLDED5066A-E no backlights

Is there a way to test the LED strips without taking the panel off. If so how. Thanks again for all the help.

It would be really helpful to have an oscilloscope. Sometimes there is voltage for the LEDs just for a brief moment, the power supply recognizes there is a problem and shuts down the driver circuit. That's something you may not be able to detect using a multimeter.

I had to repair several backlights of these cheap TVs. The problem is we don't know what's their backlight configuration. I would say you may have 5x 10 to 5x15 LEDs in series (inside the panel) which are then all in series on the PCB.

So you could remove the connector that goes to the LEDs and try to start with 25V on each of the output pairs. Assuming there are 5 strips in there it's not likely that ALL strips are damaged. So you should get light on at least one of them. If you don't get light on any of them you may slowly increase the voltage. Make sure to use a benchtop power supply with current limit set to let's say 300mA.

[mnpdreed]

Re: Proscan 50" PLDED5066A-E no backlights

5 X 14. I connected two AA batteries and checked each light individually. They all worked.

[CapLeaker]

Re: Proscan 50" PLDED5066A-E no backlights

good, now we know that the problem has to be on the PSU.

[mnpdreed]

Re: Proscan 50" PLDED5066A-E no backlights

First I would like to thank everyone for the help. Update!! Apparently when I tested each LED in the strip I missed the first LED in each strip. I bought a power supply and tried to test each pair of wires with 45 DCV. I got nothing so I broke down and removed all of the strips from the tv. On all five strips the first LED is bad. The back of the strip under those LEDs are burnt. Sorry for the confusion.

Is there a way to remove the LED and replace those that are bad. The strip is around 25 each and the tv is not worth that much but I do have LED strip from another tv if there is a way to remove.

[budm]

Re: Proscan 50" PLDED5066A-E no backlights

OK, so your meter probably was not fast enough to catch the Voltage rise before it goes into protection mode and lead to believe that the problem is in the power supply section but turns out to be bad LEDs just like other LED Backlights TV. At least now you found out you do have bad LEDs.

[mnpdreed]

Re: Proscan 50" PLDED5066A-E no backlights

Thank you again for your time and patience. Is there a easy way to remove led from the strip?

[paulstef]

Re: Proscan 50" PLDED5066A-E no backlights

1. remove the defective LED
2. remove excess solder with solder wick

3. Take a spare LED strip from another TV if you have one and cut out a piece of PCB containing a good LED one or two inches long
4. Glue that piece onto the strip to be repaired. Kapton tape and glue or double-sided tape.
5. connect the piece of PCB to the LED strip with wires.

DON'T bother trying to solder a LED onto the defective LED strip. It has big copper traces that serve as heatsink. Heating the LEDs to much during soldering will destroy them.

Don't know if you have backlights similar to these: https://www.youtube.com/watch?v=O2R3ZfCsYW4

[mnpdreed]

Re: Proscan 50" PLDED5066A-E no backlights

Thank you I will try that this weekend

[mnpdreed]

Re: Proscan 50" PLDED5066A-E no backlights

Here is an update. I bought a rework air station. I was able to remove some LED s from and old strip and replace the bad ones. First on a success. I will try and get them all done this weekend and install back in TV to see if it works. Thanks again everyone for helping.

[mnpdreed]

Re: Proscan 50" PLDED5066A-E no backlights

Decided to go ahead and complete the LED swaps. All of the bad ones were shorted. TV works perfect. Thanks everyone.

[budm]

Re: Proscan 50" PLDED5066A-E no backlights

Thanks for the follow-up, do not forget to turn down the backlights level in the user menu setup if you can.

[techd]

Re: Proscan 50" PLDED5066A-E no backlights

I have the same Proscan 50" TV experiencing the same problem. How did you determine what LED part to purchase to replace the burnt ones on the light strips?

[Glenn_Weile]

Re: Proscan 50" PLDED5066A-E no backlights

I've had success using the Digikey P/N: 1416-1222-1-ND (max 100 mA) to replace an open LED on a strip. I've also removed an LED from a strip and shorted it with a piece of wire wrap. (the customer was in a super rush for the repair and didn't want to wait for parts to come in)...

In doing so, I found I had to change the 510 K current sense resistor (0805 packaged device) coming off Pin 6 (I Sns input) to the BD92111F PMIC IC on the power supply board to a 470 K resistor...

I have a bad feeling that when these back light LED's start failing that sooner or later others will fail...

[neilc6]

Re: Proscan 50" PLDED5066A-E no backlights

I replaced three LEDs on one strip on a similar model RCA RLDED5078A-D. Tv does not have a separate backlight adjustment, just brightness. Ran it for a couple of days and not super comfortable selling it though I did tell the buyer not to run it at full btightness.

[rustyweld]

Re: Proscan 50" PLDED5066A-E no backlights

I have a proscan 50 inch tv (PLDED5066A-E) (S/N: A1305096070000235) that starts up with a great picture.Then lasts about one to two minutes and goes black. If i shine a flashlight on the screen I can see the menu and volume. If i shut it of then turn it back on it goes black after 20 to 30 seconds, then repeats the same again if i turn it of and on again. I have takened the tv apart and all the back lights work with it plugged in but go off after . I did not check the time as I was trying to see if all the lights where on but they didn't last very long. I was wondering if you could help as to diagnose the problem before I have to begin replacing parts.