Samsung T240HD won't turn on

[selldoor]

Re: Samsung T240HD won't turn on

Also with power off, meter on ohms 200 can you test that fuse 301 again and post the result.

[phx777]

Re: Samsung T240HD won't turn on

updated the results.
I thought the main board was the board with all the inputs >.>

Perhaps it's best to explain everything in Layman's, my knowledge on these things are very limited.
and I've tested the fuses, they are fine. 0.25 ohms on both

thanks for all the help!

[selldoor]

Re: Samsung T240HD won't turn on

Originally Posted by selldoor View Post
OK With your meter on VDC 20 put the black pin on pin 4 and with the red probe touch
the other pins and report the results.
Board needs to be plugged in to the mains. Still take care although you are measuring low voltages parts of the board are still high.

Not really getting through to you are we?
The above test is to be carried out with only the power supply plugged into the mains - no other boards for the moment.
The pins are on the connector CN2 in the same corner that the voltage list is

That is as Layman as I get but here is a picture

[phx777]

Re: Samsung T240HD won't turn on

Originally Posted by selldoor View Post
OK With your meter on VDC 20 put the black pin on pin 4 and with the red probe touch
the other pins and report the results.
Board needs to be plugged in to the mains. Still take care although you are measuring low voltages parts of the board are still high.



That is as Layman as I get but here is a picture

ahhhh that makes so much more sense, thanks!
I'll get on it and report back.

[phx777]

Re: Samsung T240HD won't turn on

finished testing, as marked, one returned 15v and two returned 5.2v
all others are 0

[Rtech]

Re: Samsung T240HD won't turn on

So the next step is to connect the other boards,and then take the same measurements again,and see if you still get the 15v and the 5.2v

[phx777]

Re: Samsung T240HD won't turn on

So the next step is to connect the other boards,and then take the same measurements again,and see if you still get the 15v and the 5.2v

they are close to 0 now. might have seen the 15v jump to 1v a couple of times.

[Rtech]

Re: Samsung T240HD won't turn on

Looks like it is the Logic Board that is faulty then,you already checked the Voltage regulators on there ??

[selldoor]

Re: Samsung T240HD won't turn on

No, He has not.

In the picture of the main board, thoughtfully placed upside down! on the left hand side bottom just above the screw hole there is a black square component with 2.5 legs.
On it I think it has a part number that has "33" in it.
I think it is a voltage regulator.
If you read this by retiredcaps you should be able to test it and find others on the board - we will need a better picture preferably the right way up to help.
https://www.badcaps.net/forum/showthread.php?p=261329

I notice in that picture that the board may be on an antistatic bag? If that is so please be aware that the foil on it is conductive and you should not be doing any tests with the boards sitting on it.

[phx777]

Re: Samsung T240HD won't turn on

that picture of the board is a picture I found off ebay, don't worry I'm not testing it on a antistatic bag.

I've read the guide on testing the voltage regulator, I'm not sure what it means by "Put your black probe on a ground screw". Does it mean I can just put the black probe on any large metal object? I'm not getting any readings out of any voltage regulators.

[Rtech]

Re: Samsung T240HD won't turn on

The metal part of the VGA or DVI input socket will be fine.

[selldoor]

Re: Samsung T240HD won't turn on

that picture of the board is a picture I found off ebay,

Well thanks a lot. Just wasted my time looking at it then. I am off the case.

[phx777]

Re: Samsung T240HD won't turn on

Well thanks a lot. Just wasted my time looking at it then. I am off the case.

I'm sorry you feel that way. When I uploaded that picture I thought it was a faulty power board so I didnt even take off the main board for a picture.
thanks for all your help so far, it was very helpful.



I've tested the voltage regulators (not sure if I found all of them). Most of the tests returned 0 except for the ones I marked in red.

[Rtech]

Re: Samsung T240HD won't turn on

Find the pin that the 5v would normally come into the board on, and trace the track to the nearest Voltage regulator,obviously you have to do this with the board dis-connected because it is pulling the 5v down.Also Numbers on all, what you think are regulators will be helpful.

[phx777]

Re: Samsung T240HD won't turn on

Find the pin that the 5v would normally come into the board on, and trace the track to the nearest Voltage regulator,obviously you have to do this with the board dis-connected because it is pulling the 5v down.Also Numbers on all, what you think are regulators will be helpful.

I was thinking of just buying a replacement board if I can be 100% sure it's the cause of the problem. :\

all in all, this was a pretty fun/interesting experience, I am willing to see it to the end if I can.

[Rtech]

Re: Samsung T240HD won't turn on

Well there is no certainty that it is the regulators, as other things fail also.BUT from the tests you have carried out,it is very likely to be the Logic.One test you can do,to perhaps set your mind at rest,is as follows,,,,Set up the Power supply ONLY,so you know you have 5v on that,and then plug the Backlights in ONLY(NO other board or lead to the Screen),Then take a 1KΩ resistor and hook it between the 5v pin and the ON/OFF pin on the connector,,,,that should put the Backlights on and shown the Power supply AND Inverter AND Backlights are good.

[phx777]

Re: Samsung T240HD won't turn on

Well there is no certainty that it is the regulators, as other things fail also.BUT from the tests you have carried out,it is very likely to be the Logic.One test you can do,to perhaps set your mind at rest,is as follows,,,,Set up the Power supply ONLY,so you know you have 5v on that,and then plug the Backlights in ONLY(NO other board or lead to the Screen),Then take a 1KΩ resistor and hook it between the 5v pin and the ON/OFF pin on the connector,,,,that should put the Backlights on and shown the Power supply AND Inverter AND Backlights are good.

by connector do you mean the connector that connects the ON/OFF button to the logic board? how do I know which pin is the ON/OFF pin? There are two markings on the connector. There is a green dot on the connector, and a black mark on one of the cables.

or did you mean the ON/OFF on the power board?

[Rtech]

Re: Samsung T240HD won't turn on

on the Power Board, as that is the ONLY one you will have on !!!!!! again NO Logic BOard, Power supply ONLY with just the Backlights plugged in NOT the other lead that goes to the screen...

[phx777]

Re: Samsung T240HD won't turn on

on the Power Board, as that is the ONLY one you will have on !!!!!! again NO Logic BOard, Power supply ONLY with just the Backlights plugged in NOT the other lead that goes to the screen...

ah ok thanks for clearing that up, gotta go buy a resistor now. So basically, it is to trick the power board into turning on to giving power to the backlight right?

[Rtech]

Re: Samsung T240HD won't turn on

Correct...you could as an alternative put 3V from a battery between any of the GND pins and the ON/OFF Pin....same effect.