TCL - L50E3020FS not turning on

[Amraks]

TCL - L50E3020FS

Symptoms: not turning on.

PSU: 81-PE421C8-PL290AA REV:C.0 1345

MAIN: 08-T51F102-MA200AA / 4A-LCD50E-CM1GTA / 08-T51F102-MA300AA / GLZ112791B / 20112053MA0394 / 40-MT51EU-MAE2HG

Filter Cap Voltage: 393.1V

BL_ON = 0v
P_ON = 3.2v
A_DIM = 0v
GND = 0v
24v = 0v
24v = 0v
---------
P_DIM = 0v
GND = 0v
3.3VSB = 3.3v
GND = 0v
GND = 0v
24V= 0V

Have tried jumping PS_ON and 3.3VSB same results. Not sure if I would be wasting my time with a recap.
Did recap 50v 4.7uf cap.
PFC voltage seems fine.

[dick_barton]

Re: TCL - L50E3020FS not turning on

Maybe PS_ON needs to go to 0V using a 1K resistor?

[Amraks]

Re: TCL - L50E3020FS not turning on

Hey Tried 1k resistor to ground. did not work.
I am in the process of suspecting OptoCouplers. I will upload some photos very shortly.

[dskall]

Re: TCL - L50E3020FS not turning on

What was voltage at ps_on with resistor?

[Amraks]

Re: TCL - L50E3020FS not turning on

Here is a photo of the PSU best photo I could get.

[Amraks]

Re: TCL - L50E3020FS not turning on

What was voltage at ps_on with resistor?

3.28v

[dick_barton]

Re: TCL - L50E3020FS not turning on

Power supply schematic available if you would like to download it.

https://www.scribd.com/doc/316392645...1C8-PWE1XG-pdf

[dick_barton]

Re: TCL - L50E3020FS not turning on

When you connected PS_ON to 3V3STB did have the mainboard disconnected at that time?
P_On should be at 0V and at 3.3V when ON, according to the schematic.

[Amraks]

Re: TCL - L50E3020FS not turning on

Yes all boards were disconnected.

[Amraks]

Re: TCL - L50E3020FS not turning on

Here's the full schematic
I will check this out tommorow...

[dick_barton]

Re: TCL - L50E3020FS not turning on

Check your voltages around U401 especially C406, DS2 & DS3. The chip drives the transformer to derive the 24V secondary supply.

[dskall]

Re: TCL - L50E3020FS not turning on

Just try grounding ps_on pin

[Amraks]

Re: TCL - L50E3020FS not turning on

Nothing at all Dskall when grounding ps_on pin.

[budm]

Re: TCL - L50E3020FS not turning on

The PS-ON is working fine otherwise you will not have that PFC Boosted Voltage of 393VDC as reported in post 1.
So you need to find out the 24V SMPS U401 has VCC at pin 7 for it to run or not.
Also disconnect the load form the 24Vdc out connector to see if the 24V will come up.
BTW, the main board is not sending the BL-ON and the Dim signals either.

[Amraks]

Re: TCL - L50E3020FS not turning on

Hey Budm I pulled all them connectors out when forcing the power supply on.
Nothing came up at all.

On the U401 Pin 7 VCC I get 16.0v

[budm]

Re: TCL - L50E3020FS not turning on

The thing is when you have all the connector back in place you do have the PS-ON but not the BL-ON or the dimming signals which indicates that you also have main board problem, but then it can be due to no 24V so those two signals may be locked out.
At this point, it is the 24V power supply section that needs to fixed first.
16V for VCC may be OK but I do not know until we get the spec sheet of that U401 to find what the minimum Voltage requirement is.
I see the gray rectangular cap laying on its side next to the heatsink of the U401, lift one leg off the board and check its capacitance and report what the Value of that cap is as measured and as printed on the cap. You may have bad U401 also.
Did you already check the caps and diodes on the cold side of that 24V supply? Also check the small lytics cap laying on its side next to that 24V transformer.

[Amraks]

Re: TCL - L50E3020FS not turning on

Got the datasheet.
Will be testing that cap and others won't be able to test esr I think I need to invest in a meter.

[Amraks]

Re: TCL - L50E3020FS not turning on

Minimum voltage for VCC line is 0.3v Maximum is 25.0v

Also the measurements and Print for the cap are what follows.
Capacitance Test: 22.02 nF
mmkp82
223j1000
I checked all diodes on the cold side.

Cap you told me to check has already been recapped. which would be 50v 4.7uF I had plenty thought it wouldn't hurt.

[Amraks]

Re: TCL - L50E3020FS not turning on

Check your voltages around U401 especially C406, DS2 & DS3. The chip drives the transformer to derive the 24V secondary supply.

Hey checked my voltages around C406 and it came back with 390v's

DS2v & DS3 had no voltage in these places. on pin 1 and pin 3. so i would assume pin 2 to have no voltage either.

Is this a bad transformer as its looking that way now.

[Amraks]

Re: TCL - L50E3020FS not turning on

Transformer pulled out of circuit readings
Primary Side
Pin 6 - 2 : 0.3ohms

Secondary Side.
Pin 9 -13 : 0.2ohms

pin 11 - 14 : 0.2ohms