Samsung LE37A556P1F Flashing red light

[Jasgriff]

Re: Samsung LE37A556P1F Flashing red light

I haven't got any loose resistors here that the moment to try it out I will have to pick some up tomorrow.

Is there anything else I should pick up while i'm at it?

[Jasgriff]

Re: Samsung LE37A556P1F Flashing red light

Also when Connector 2 is not connected to the mainboard the backlight comes on really bright so how can it do that with no BL_ON signal connected?

[budm]

Re: Samsung LE37A556P1F Flashing red light

What you can do is to set your meter to DC AMP mode (you know how to do that right) and just connect the probes of the meter to the E and B, that should do it also.

[budm]

Re: Samsung LE37A556P1F Flashing red light

The inverter may have Pulled up resistor on it already.

[budm]

Re: Samsung LE37A556P1F Flashing red light

At this point, we want to verify that the transistor is being told to turn on, it should goes off when the TV is turn on, so it sounds like you have main board problem.

[Jasgriff]

Re: Samsung LE37A556P1F Flashing red light

What you can do is to set your meter to DC AMP mode (you know how to do that right) and just connect the probes of the meter to the E and B, that should do it also.

There is a pic of my meter at the beginning of this post I am guessing that the dial need to be at point to the very bottom with the probes in the same place as if i were measuring diodes?

[Jasgriff]

Re: Samsung LE37A556P1F Flashing red light

Try shorting out that Base and the Emitter with the 100 Ohms and see if the BL is ON.

Ok I did that with the multimeter and the back light turned on.

[budm]

Re: Samsung LE37A556P1F Flashing red light

Well, that main board is not working as far as the BL ON signal, second thing will be that you can now turn on the backlights for the light source, then you should see the pictures on the screen, if not, then you have more problems on the main board beside no BL ON signals. Power supply section on the main board will have to be checked next since it has a bunch of voltage regulators on the main board.

[Jasgriff]

Re: Samsung LE37A556P1F Flashing red light

Well, that main board is not working as far as the BL ON signal, second thing will be that you can now turn on the backlights for the light source, then you should see the pictures on the screen, if not, then you have more problems on the main board beside no BL ON signals. Power supply section on the main board will have to be checked next since it has a bunch of voltage regulators on the main board.

Backlight comes on but the screen has not picture at all.

I can see about 5 voltage regulators on this board. Do you want the readings from all of these along with their model numbers or should they all be the same?

[budm]

Re: Samsung LE37A556P1F Flashing red light

They will not be all the same, there should be some kind of marking on those regulators, we need the numbers so we can look up the spec for them.

[Jasgriff]

Re: Samsung LE37A556P1F Flashing red light

Ok

CH? 17-33 0818BG
CH? 17-18 0814BG
ch? 1117 0819BG x 2
17-25 0807AG
KIA 78D015F

Those are the ones I can see on the main board.

[budm]

Re: Samsung LE37A556P1F Flashing red light

CH? 17-33 0818BG: More likely to be the same as LM1117 3.3V FIXED Regulator
CH? 17-18 0814BG: More likely to be the same as LM1117 1.8V FIXED Regulator
ch? 1117 0819BG x 2: More likely to be the same as LM1117 Variable Regulator, the voltage will set by two resistor on one of the PIN.
17-25 0807AG: More likely to be the same as LM1117 2.5V FIXED Regulator
KIA 78D015F: More likely to be the same as LM7805 low drop out type 15V FIXED Regulator

So just look up the datasheet for them.

[Scenic]

Re: Samsung LE37A556P1F Flashing red light

KIA 78D015F: More likely to be the same as LM7805 low drop out type 15V FIXED Regulator

KIA78D015F is a 1.5V voltage regulator. Not 15V.

[budm]

Re: Samsung LE37A556P1F Flashing red light

scenic, thanks for finding the spec sheet, I should have seen the 0 (ZERO) in front of the 15, which makes sense, thanks.

[Scenic]

Re: Samsung LE37A556P1F Flashing red light

No prob. It's a weirdo VR though.. Apparently it's a "standard" 78xx series voltage regulator, but with a completely oddball 1.5V output voltage.
(the lowest the actual standard/jellybean 78xx's go to is 5V)

I thought it was 15V too.. but that voltage seemed really odd for a LCD TV mainboard.. so I went digging a bit

[budm]

Re: Samsung LE37A556P1F Flashing red light

I still do not know which IC will be using 1.5v for VCC, the cpu will more likely to use the 1.8v. But we will find out if he can find what went out on the main board.

[Jasgriff]

Re: Samsung LE37A556P1F Flashing red light

Ok thats all of the readings from the voltage regulators listed.

All seem to be performing ok.

Not sure how to test what the variable regulators should actually be outputting though?

[budm]

Re: Samsung LE37A556P1F Flashing red light

The one with the adjustable output using the resistors at the adjustable pin, there is a note in the spec sheet on how to set the out put voltage by calculating the value of the two resistors. You will have to Ohm out the two resistor and see if you put those value into the formula to see what it should have at the output.

[Jasgriff]

Re: Samsung LE37A556P1F Flashing red light

The one with the adjustable output using the resistors at the adjustable pin, there is a note in the spec sheet on how to set the out put voltage by calculating the value of the two resistors. You will have to Ohm out the two resistor and see if you put those value into the formula to see what it should have at the output.

Ok I have tested the first set and these are the results and my calculations do they seem correct?

The second set of readings are attached and they seem to be alot closer to what I would be expecting to find.

[Jasgriff]

Re: Samsung LE37A556P1F Flashing red light

Just realised that there are more regulators on the underside of the board

There are another 3 which will be quite difficult to test without taking off off both boards and setting them up away from the tv?