Element ELEFW40C won't turn on.

[budm]

Re: Element ELEFW40C won't turn on.

Yes, the main main cap is that 120uF 400VDC cap.
How about those Voltages? That will give us more clues.

[Spork Schivago]

Re: Element ELEFW40C won't turn on.

With the camcorder, this is the best I can do without zooming in and taking pictures in pieces. When my wife gets home, we'll try her fancy cell phone. It might have a better camera.

Give me a sec and I'll get those voltages. I gotta take care of the baby while I'm doing this, so it's taking a little longer than it normally would.

[budm]

Re: Element ELEFW40C won't turn on.

OK, I can see that the cold side of the power transformer has two windings, the rectifier diodes for each winding look to be connected in parallel. So we need those Voltage reading the in the picture I have marked.

[Spork Schivago]

Re: Element ELEFW40C won't turn on.

Okay, I got the voltages now.

Cap:   37.50VDC
Diode 1: 12.12VDC
Diode 2: 12.12VDC
Diode 3: 37.5VDC
Diode 4: 37.5VDC

[budm]

Re: Element ELEFW40C won't turn on.

Okay, I got the voltages now.

Cap:   37.50VDC
Diode 1: 12.12VDC
Diode 2: 12.12VDC
Diode 3: 37.5VDC
Diode 4: 37.5VDC

OK, as expected.
Now I know why you are getting the reading of 37V on that Diode of the Boost converter, that 37V is the feeding Voltage to the Boost converter that gets converted to higher Voltage to drive the LED strings but since it is not running which can be due to no BL-ON command to turn on the Booster circuit or the booster is bad, but from what you describe the problem with the TV it sounds like there is no action going on in the main board section. The power supply is fine.

[Spork Schivago]

Re: Element ELEFW40C won't turn on.

OK, as expected.
Now I know why you are getting the reading of 37V on that Diode of the Boost converter, that 37V is the feeding Voltage to the Boost converter that gets converted to higher Voltage to drive the LED strings but since it is not running which can be due to no BL-ON command to turn on the Booster circuit or the booster is bad, but from what you describe the problem with the TV it sounds like there is no action going on in the main board section. The power supply is fine.

Okay Budm. The BL-ON command is what turns the backlighting on. Is that with every type of TV? What I mean is do all TVs have a BL-ON command?

How can we rule out if the booster is bad? And when you say booster, do you mean the boost converter circuit, or is there an actual component called a booster?

What should I do at this point in time? Start checking transistors on the main board section?

[budm]

Re: Element ELEFW40C won't turn on.

Okay Budm. The BL-ON command is what turns the backlighting on. Is that with every type of TV? What I mean is do all TVs have a BL-ON command?

How can we rule out if the booster is bad? And when you say booster, do you mean the boost converter circuit, or is there an actual component called a booster?

What should I do at this point in time? Start checking transistors on the main board section?

They all do, TV uses at least these 3 command signals:
PS-ON to turn on the rest of the power supply.
BL-ON to turn on backlights circuit.
DIM to control the backlights level.
The names may vary. I.E. PWR-ON may be used instead of PS-ON.

"How can we rule out if the booster is bad? And when you say booster, do you mean the boost converter circuit" I use Booster since we already know what we have been talking about already. You need to find the LED driver IC which is most TV uses for TV with LED backlights, the IC will have Boost converter GATE DRIVE output to drive the external MOSFET for the boost converter.

Example of LED driver IC:
MAP3202-ETC

[Spork Schivago]

Re: Element ELEFW40C won't turn on.

Even really old CRTs have these commands as well? I knew of PS-ON.

Also, I asked this the other day but I don't think I got a response. I found what appears to be a transistor in an SOT-23 package. The bottom two legs are both measuring as around 5VDC. Is this normal? I thought one would read as GND and the other as something voltage. Not a positive voltage on both the bottom terminals.

I was thinking this might be normal. I was thinking the transistor is being used as a switch and until that one terminal reads GND, it's essentially OFF. Am I right in thinking this or is there a problem there?

[Spork Schivago]

Re: Element ELEFW40C won't turn on.

Here's something else that I find very strange. This metal bar, that I thought was supposed to be a GND is actually reading 37V. There's a chip underneath it, I think it might be a voltage regulator. There's three terminals on the bottom of it and the middle one doesn't appear to be connected to anything, then there's the big fat tab at the top. I measure the voltage of the bottom terminals. The two outside ones read 0VDC, but the middle one reads 37VDC. The big fat tab reads 37VDC as well. Is this normal?

[budm]

Re: Element ELEFW40C won't turn on.

Even really old CRTs have these commands as well? I knew of PS-ON.

Also, I asked this the other day but I don't think I got a response. I found what appears to be a transistor in an SOT-23 package. The bottom two legs are both measuring as around 5VDC. Is this normal? I thought one would read as GND and the other as something voltage. Not a positive voltage on both the bottom terminals.

I was thinking this might be normal. I was thinking the transistor is being used as a switch and until that one terminal reads GND, it's essentially OFF. Am I right in thinking this or is there a problem there?

It depend how the Transistor is being used, you can use Transistor that does not have any pin directly connected to ground, I.E. Linear regulator.
Unless you know how the connections of the transistor are then you cannot really tell until you trace out the circuit, and what appear to be Transistor it may not be unless you look up the spec sheet.

[budm]

Re: Element ELEFW40C won't turn on.

Here's something else that I find very strange. This metal bar, that I thought was supposed to be a GND is actually reading 37V. There's a chip underneath it, I think it might be a voltage regulator. There's three terminals on the bottom of it and the middle one doesn't appear to be connected to anything, then there's the big fat tab at the top. I measure the voltage of the bottom terminals. The two outside ones read 0VDC, but the middle one reads 37VDC. The big fat tab reads 37VDC as well. Is this normal?

That should be the MOSFET for the boost converter. The big tab should be Drain pin. If you look at the PDF I provide, then you will understand why you are see the 37VDC when the Boost converter is not running.

[Spork Schivago]

Re: Element ELEFW40C won't turn on.

Okay. Is that the PDF for the LED Driver IC that will explain it? I've glanced through it. I went back to the board and wrote down the IC numbers I found. There's an 8-pin in the booster circuit area (a small package size) that has written on it:

F24984
SN51DP
   P

There's one that has about 28-pins or so on it, it has written on it:

F25565
OB6220VP
R

That mosfet has written on it:

D4454
GA4P1B

The baby's crying and I have to take care of her, but my wife should be getting home soon and can take over with the baby. That'll give me more time to work on this. I couldn't find a datasheet for the F24984 IC but that's in the booster circuit location and I was thinking maybe that's the LED driver IC

[vinceroger69]

Re: Element ELEFW40C won't turn on.

budm im still learning so bear with me but what is the purpose of the eeprom in a tv i understand it stores the sound/channel settings etc but does it send bl on ps on signals too?

[budm]

Re: Element ELEFW40C won't turn on.

The micro controller (MICON) of the TV sends out the command signals.
Some example:
http://www.electronicrepairguide.com...r-circuit.html

[vinceroger69]

Re: Element ELEFW40C won't turn on.

The micro controller (MICON) of the TV sends out the command signals.
Some example:
http://www.electronicrepairguide.com...r-circuit.html

Thanks budm will have a read of this

[Spork Schivago]

Re: Element ELEFW40C won't turn on.

I'm thinking the small 8-pin IC in the booster circuit area is the LED Driver IC. The one that says
F24984
SN51DP
P

on it. I can't find much information on that IC at all. In fact, I can't seem to find any information on the other one either. I haven't looked for a datasheet for the MOSFET, just those two. The 28-ish pin one is clear on the other end of the board and probably doesn't have anything to do with the LED driver circuit. Without a datasheet, it'll be hard to test that chip, because I won't know what pins are supposed to be what.

Some sites list that IC as an LCD power supply chip...here's a picture of it:
https://translate.googleusercontent...._AP0Pb0j1dV06A

[Spork Schivago]

Re: Element ELEFW40C won't turn on.

In this picture here, the IC labeled UB801 might be the SN51DP IC....

http://bbs-static.21dianyuan.com/att...zhy6y2wq2q.jpg

What do you think Budm?

[budm]

Re: Element ELEFW40C won't turn on.

Well if that is the correct IC, I do not see enable pin so it may may mean that there is switched MOSFET some where on the board that is turned on so the IC will get the 12V to run, so see if you do have 12V on VCC (Vin) pin or not.

[Spork Schivago]

Re: Element ELEFW40C won't turn on.

I must be learning something here Budm because before I even read your post, I checked the VIN pin and I do have 12VDC on it.

[Spork Schivago]

Re: Element ELEFW40C won't turn on.

It's a very small chip, I don't know if I can check any of the inner pins. The outer pins are fairly easy to check, I can just rest my probe on the side of them, but those inside pins will be an entirely different story, if I have to check any of them.

What's the FB and COMP Pins stand for and what are they used for? I'm trying to search the internet to find out, but I'm having poor luck. With FB pin, I see it might be something called the Feedback Pin.