Proscan Plded3996a-c2

[_N_]

Man there's nothing in these Tvs these days wow tiny little boards compared to the Sammy. This one ill keep to turn it into a led monitor for the pc :P

Symptoms Are :
Tv red power led turns on when plugged in, Once power for the remote is pressed led becomes Blue and remains. No back-light Leds come on at all, not even a flicker.

Ive checked the through hole components in the pics they have dots, all seem to register on the little trans tester as what they are, none burnt.

In the pics ive tried to take readings, I can already see
"Bud, typing inverter/Pwm circuit , here we go again" what are the voltages."
Not sure sure if its CAP Ground leg or chassis .
To take those readings for the inverter IC ,Youll ask and ill measure.





http://www.datasheetlib.com/datashee...conductor.html

http://www.scribd.com/doc/255967649/...Control#scribd





tried to do all the homework so you guys don't waste time

[budm]

Re: Proscan Plded3996a-c2

Since this unit only have one big yellow power transformer and you are getting indicator LED to come on then the main power supply is functioning so no need to check that power MOSFET in the primary side which drives that power transformer.
It is more likly to something in the LED backlights driver circuit or the LED or it the driver is not getting BL-ON signal.
Can we see the whole back side of the TV? I cannot see where the LED BACKLIGTS wires are at, it looks like the connector with the red and black wires.

[_N_]

Re: Proscan Plded3996a-c2

Those red and black wires disappear into a little slit in the caseing under the psu/inverter. the whole tv must weigh like 15 lbs max lol.
I think there just connected to the led strips inside, I didnt want to dismantle the complete thing in case a break the screen,limited work space.
BUT if its required, NP. needed?

[_N_]

Re: Proscan Plded3996a-c2

See. In the 3rd pic I took, where you see the voltages of the backside of the board in red ,
Under the N channel Fet

theres 2 tiny little 3 pin SOT-23 ( i think) Smds .
1 is 3pin NpN and checks good the others a 3 pin Diode and
Theres 1 tiny Zdiode (gives voltage both ways)

these are by the inverter ob3350

[jetadm123]

Re: Proscan Plded3996a-c2

Did you check the 15N10 FET on the bottom for shorts?

[_N_]

Re: Proscan Plded3996a-c2

None of the 3 contact points beep on my meter, I tried in every combination.

[budm]

Re: Proscan Plded3996a-c2

OK, the Voltage on the 100uF 100Vdc cap whcih is the filter cap for the LED driver Voltage boost converter circuit (the TOROID Inductor, the SMD Power MOSFET on the bottom of the board, the two rectifier diodes stacking on top of each other next to the TOROID). The 20.8BDC reading on that 100uF 100Vdc is too low. Was the Voltage reading taken without the LED connector in place?
So beside check the MOSFET for shorts, you need to check the diodes also.

[Agent24]

Re: Proscan Plded3996a-c2

Theres 1 tiny Zdiode (gives voltage both ways)

Do you mean when testing in diode test mode with your meter? What is the voltage measured? Maybe it's shorted.

[_N_]

Re: Proscan Plded3996a-c2

Just retested same reading at the cap legs of the 100uf 100v 20+v

the diodes tested good i pulled them off board to test.

[budm]

Re: Proscan Plded3996a-c2

Just retested same reading at the cap legs of the 100uf 100v 20+v

the diodes tested good i pulled them off board to test.

Without the LED connector attached?

[_N_]

Re: Proscan Plded3996a-c2

Do you mean when testing in diode test mode with your meter? What is the voltage measured? Maybe it's shorted.

im pretty sure its a Z-diode cause the tiny number can be read and goggled what it was.
4.4 1 way and 4.8 the other

[_N_]

Re: Proscan Plded3996a-c2

Without the LED connector attached?

no no before, when i was testing them off board. None were shorted and all showed up with there diode symbol.

[budm]

Re: Proscan Plded3996a-c2

I am talking about the DCV reading on that 100uF 100V that you are getting only about 20VDC instead of something >50VDC.

[_N_]

Re: Proscan Plded3996a-c2

I am talking about the DCV reading on that 100uF 100V that you are getting only about 20VDC instead of something >50VDC.

the 2 stacked diodes theres browning on the pcb from the heat, I did also pull those earlier and checked them to see if they were fried and they measured off the board like diodes.

[budm]

Re: Proscan Plded3996a-c2

I know, but I need to know what DCV do you get on that 100uF 100V when the LED connector is attached.

[_N_]

Re: Proscan Plded3996a-c2

I am talking about the DCV reading on that 100uF 100V that you are getting only about 20VDC instead of something >50VDC.

At that 100V 100uf cap it gives me 20.8v dc, with probes placed directly pn the 2 legs of the 100uf 100v and meter set to DC AND thats with Every cable to the main board currently connect.
If you need a voltage test on something, id be happy to.

[budm]

Re: Proscan Plded3996a-c2

I want the reading on the cap WITHOUT the LED connector plugged into the board to verify that there is no shorts in the wiring to the LED assembly.

[_N_]

Re: Proscan Plded3996a-c2

Also Ive read on here so long that capxon zapxon and every thing that ens with Xon in it is so bad I pulled all the Elctros caps and all were within there UF rating, I have a separate Cap meter (the joys of Ebay :.}.. )

[_N_]

Re: Proscan Plded3996a-c2

I want the reading on the cap WITHOUT the LED connector plugged into the board.

20.8vDC without led connector plug

[budm]

Re: Proscan Plded3996a-c2

OK, that means the MOSFET is not switching on and off and it just passes the input Voltage right to the output without producing the boosted Voltage needed for the LED.
So you need to find out what DCV you have on the VCC pin and the GND pin of that 8-pin SMD IC.
Did you download the spec sheet for that IC? If you did, then you should upload it.