Proscan 50" PLDED5066A-E no backlights

[mnpdreed]

I have a Proscan PLDED5066A-E that has sound but no back lights. When it is powered on, the red standby light will turn blue and you can hear sound but no back lights at all.


SMPS – AY 128D-4SF11
IC 1 – L6562A
L2 – AY 8LE00187
All reading is with the black test lead on negative side of the filter cap (C-13)

C13 filter cap – 173.1 V

C15-173.1V and 81.8V

D18- 383V and 122.2V

B1-121.1V and 121.1V

L2 - 0mV and 0mV
117.6V and 121.1V

C14- 121.5V and 10.2mV

10.5mV-----
Q2- 120.1V--------------
4.56V------

10MV---R83---1.3mV
10mV---R29---10mV

C4-(-)1.4mV (+)15.5V
T2F 195.4mV and 189.1mV

Thank you for the help.

[mnpdreed]

Re: Proscan 50" PLDED5066A-E no backlights

pic

[CapLeaker]

Re: Proscan 50" PLDED5066A-E no backlights

Well... you did a whole bunch of work, measuring all kinds of things. However it doesn't say too much.

So first, check if the back lights do get BLon signal on the PSU coming from the main board. If that BLon is there, but no backlight, check the voltages on the LED backlight connector. You may also want to use the min / max function on your DMM. Maybe you have short or an open on your LED backlight strings.

[mnpdreed]

Re: Proscan 50" PLDED5066A-E no backlights

Thanks for helping. Sorry about all those unnecessary voltage reading. I am a novice so I was trying to get as much information out as I could on the first post.

I don't have the connector readings with me but I do recall the top connector (CON1) when "on" read .662V and "off" read 1.910V.

Con3 (13 pin) and Con 2 (4 pin) were getting the correct voltage as marked on the backside of the board.

Con 2F with GRN, NC, ADJ, and BLon I don't recall the readings but I will check and post it tonight.

Thank you again for helping.

[mnpdreed]

Re: Proscan 50" PLDED5066A-E no backlights

I have been searching the posts and found the cap C10F should read 385V and ground. "budm" stated the cap is connected to the primary side of T2F. The readings I got on C10F 182.6 MV and .3 mV and T2F 189.1 mV and 195.4 mV. I don't know if this will help but I thought I would add it just in case.

[CapLeaker]

Re: Proscan 50" PLDED5066A-E no backlights

We really need to know what is on those connectors on the PSU. Measure and post them with the corresponding pin outs, so we have a picture what works and what doesn't.

[mnpdreed]

Re: Proscan 50" PLDED5066A-E no backlights

From top to bottom with power on.

Con1
.639 mv
0 mv
2.6 mv
6.2 mv
-.7mv
.3 mv
1 mv
1 mv
0 mv
-2 mv

Con2f
-2.5 mv GND
3.9 mv NC
4.02 v ADJ
4.56 v. BL-on

Con2
25.62 v
25.62 v
-4.3 mv
-4.3 mv

Con3

11.90 v
11.90 v
-3.6 mv
-3.6 mv
-3.6 mv
5.02 v
5.02 v
5.04 v
4.42 v
5.02 v
5.02 v
-6.3 mv
-6.3 mv

[mnpdreed]

Re: Proscan 50" PLDED5066A-E no backlights

Pic

[CapLeaker]

Re: Proscan 50" PLDED5066A-E no backlights

all right, so all power rails are on, PSon and BLon is there, ADJ is there, but still no backlight. The backlight has 5 strings in your case (con1). Unplug that connector and see if one of them is shorted or open. Also try to measure and see if the voltage ramps up and back down or if there is nothing at all.

So either you got a short or open LED backlight string(s) or the PSU is indeed not putting any backlight voltage out for some reason. Check those 4 large diodes underneath con1 and the 2 large resistors maybe those are bad?

[mnpdreed]

Re: Proscan 50" PLDED5066A-E no backlights

OK I will check it and post the findings. Do I check the whole LED string as I would a single diode? I don't know if this is anything that would help, T2F has 189.1 mV and 195.4 mV on primary side. The secondary side is connected to the 4 large diodes.

[mnpdreed]

Re: Proscan 50" PLDED5066A-E no backlights

All 4 diodes (MUR 460) in circuit tested .410 and OL in diode mode with DMM. Resistor are 10 ohms tested 5.3 in circuit

[mnpdreed]

Re: Proscan 50" PLDED5066A-E no backlights

When powered on with leads on con1volts start at -011.4 mv peak at 1.880 V then drop to .639v. The earlier post has the first reading as .639 mv and it should have read .639 Volts

[mnpdreed]

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.

[mnpdreed]

Re: Proscan 50" PLDED5066A-E no backlights

Any suggestion on what to do next. Thanks for the help.

[CapLeaker]

Re: Proscan 50" PLDED5066A-E no backlights

When powered on with leads on con1volts start at -011.4 mv peak at 1.880 V then drop to .639v. The earlier post has the first reading as .639 mv and it should have read .639 Volts

are these voltages measured in DC? The voltages are low, almost like you had the DMM set to AC, that low. What happens when you disconnect the LED backlight and measure con1?
con1 has 5 pairs of LED's. You can test them separately, with variable bench power supply, however with the LED's being behind the diffuser, a bad LED can be easily missed.

I am looking for a very quick ramp up in power on con1. To rule out the backlight, you may have to take it apart.

[mnpdreed]

Re: Proscan 50" PLDED5066A-E no backlights

Meter is set on DC. When CON1 is unplugged 011.1 mV then peaked at 2.06v drops to .639v DC. It is like no voltage is coming from or going to T2F with or without con 1 connected.

[budm]

Re: Proscan 50" PLDED5066A-E no backlights

Can you take really good clear straight shot pictures of the whole top side and the bottom side of the power supply-LED driver board?

[mnpdreed]

Re: Proscan 50" PLDED5066A-E no backlights

Thanks for helping. Here is the pics

[CapLeaker]

Re: Proscan 50" PLDED5066A-E no backlights

Second pic top left corner, seems to be some SMD components that have a different brownish colour? Can't read it, as the pic is a bit blurry. Is that white round sticker for decoration?

[mnpdreed]

Re: Proscan 50" PLDED5066A-E no backlights

The two white pieces are plastic tabs that hold the clear plastic over the back. I can take take closes up of different sections of the board if that will help.