ELEMENT ELEFQ462 led/lcd power problem

[ilikesteel]

Re: ELEMENT ELEFQ462 led/lcd power problem

Tom66-budm,

please explain the process of how to power up the main board with a battery or a current limiting supply. you guys have just jumped leaps and bounds past me! do I completely remove it from the TV connections?

I watched the video but I'm still unsure.

you'll have to lead me by the hand on this one, but I surely want to try!

if all else fails, can I get a replacement main board? I did a check but could not find one with that particular number.

do you think the short is in the immediate are of the smd that I removed?

much thanks, looking forward to your explanation.

thanks

frank

[tom66]

Re: ELEMENT ELEFQ462 led/lcd power problem

What you need to do is insert a resistor of around 2.2 ohms, rated for 5W dissipation, in series with one charged 1.2V battery. This gives you a ~500mA power source. (I = V / R = 1.2 / 2.2 = 0.545A) Importantly, the voltage is limited to about 1.2V, which prevents damage as that regulator type cannot output more than 1.2V.

Then attach the negative of the battery to a ground point.

It may be a good idea to buy a battery holder and solder the kit up, as it will be a lot more reliable.

Freeze spray suspect area. Try small parts of the board at the time.

Touch the positive end, through your resistor, to the output. This will make the faulty area heat up.

If the heating isn't significant enough, then you'll need to increase the current, so use a 1 ohm resistor to get around 1.2 amps.

[ilikesteel]

Re: ELEMENT ELEFQ462 led/lcd power problem

tom66,

sorry tom, some of what your saying makes a little sense, but I'm not too quick on the uptake on certain parts of what you just described.

is the main board completely disconnected from the tv for this type of testing?

also, after I rig up the test jig, you're saying connect the neg of the battery to a gnd point on the board, (the corner of the board where the screws attach the board to frame)?

what am I actually touching the pos end with resistor to? some component on the board? how would I know what to look for and what terminals of the device I should touch.

I guess I'm missing the concept, bear with me, I can learn this.


most nicad camera batteries are 1.5. can I buy 1.2v batteries at radio shack?

please excuse my ignorance.

thanks so much

frank

[tom66]

Re: ELEMENT ELEFQ462 led/lcd power problem

Most NiCAD are 1.45V max during charging and 1.2 ~ 1.35V when not being charged.

The negative of the jig needs to go to ground.

The positive needs to go to the test point which is pin #2 of the regulator (but on the board... the regulator should be not present.)

The jig should be set up like this

[ NEGATIVE ] -- (- Batt +) -- ( Resistor ) -- [POSITIVE]

[ilikesteel]

Re: ELEMENT ELEFQ462 led/lcd power problem

Tom66,

OK Tom I understand what you're saying. let me say it back to you. the theory is I'm going to put a small + voltage to pad # 2 of the removed smd.

pad # 2 we know has a short to gnd. the NEG end of the battery is connected to gnd on the board. essentially I'm putting a small + voltage to gnd through a resistor. spray surrounding area of board with freeze spray. by doing that what ever component is shorted to ground will get warm and the frost should melt faster on that component than other components.

again, this is with the board completely removed from the TV and no cable connections. what component do you expect to have this short, a cap?

I did watch the video you posted, but the gentleman never showed exactly what he was doing. I hope it's that easy!

A schematic would be nice wouldn't it? I can't find anything for the Element.

I'm off to gather the things I need.

Thanks very much,

frank

[tom66]

Re: ELEMENT ELEFQ462 led/lcd power problem

That's me in the video... it's more clear if you understand I am using one of these...

...where I can set the current precisely, to prevent damage. I'm not using a battery.

In your case, the resistor is there to provide a basic current limit which a lab power supply has built in. Remember to get a high power resistor 5W or so, because a 1/4W standard resistor will get hot very quickly and probably burn out.

[ilikesteel]

Re: ELEMENT ELEFQ462 led/lcd power problem

Tom66,

great Tom, I'm off to radio shack for parts. it looks like almost everything on the board is surfaced mounted. wow, some of the components look almost impossible to desolder and replace. I'm getting a nervous feeling.

what's you best guess as to the bad component?

thanks, will report later.

thanks again
frank

[tom66]

Re: ELEMENT ELEFQ462 led/lcd power problem

My guess: Large MLCC (multilayer ceramic capacitor) short. 1206 size, easy to remove and replace. (I regularly work with 0603, but they're a bit harder to work with.) It is fairly common, if the board was flexed when first installed at the factory, or if the TV was bumped, or sometimes just random chance.

[ilikesteel]

Re: ELEMENT ELEFQ462 led/lcd power problem

Tom66,

Thanks for the description of what I may be looking for on the board. radio shack had no resistors, did buy the battery holder.

went to a samsung/sharp service center. this guy does all warranty work for samsung and sharp. he had a small amount of high wattage resistors left including a 2.2 ohm 5w and a 1 ohm 10W. he said he doesn't need them anymore and gave me both resistors free.

so now I'll attempt to complete troubleshooting this one.

what is the damage if this cap shorted to gnd. any other components possibly could be bad because of it? what about the smd that I removed?

thanks so much

frank

[ilikesteel]

Re: ELEMENT ELEFQ462 led/lcd power problem

Tom66,

I was just about ready to make the test. I mocked up the battery holder, soldered the gnd wire to a gnd on bottom of board. had the 2.2 ohm resister soldered between the +battery and the wire lead. I was attempting to solder the + lead to the pin # 2 pad when the pad came loose. I think I can repair or at least get around that problem. perhaps I shouldn't have done it that way. what way would you have connected the + lead to pin # 2 pad?

however, when the pad lifted up off the board, I decided to check to see what side of the smd was shorted. the short is connected via the tab part of the board to gnd. on the other side of the pad where it broke no shorts to gnd.

I started checking from gnd to all the caps in the area. all the caps I tested had some ohm readings on the 2K scale. ocassionally one end of the cap appeared to be connected to gnd.

however, cap C114 circled in red showed short from gnd to each end of the cap, and when I went across the cap. no other cap did that. could this little guy be the problem? it looks shorter than a 1206. how can you determine the value? OH what I would give for a schematic.

thanks Tom, will eagerly wait your thoughts on this one.

frank

[tom66]

Re: ELEMENT ELEFQ462 led/lcd power problem

Pin 2 is connected to the tab pin, so as long as you can solder to the tab that will be fine. I would have just touched it to the board for a short period of time. I wouldn't leave it continuously, you don't need to and it might cause damage.

As for which cap is bad, the problem is there may be several in parallel, so they could show short even if they are not. So, you need to try and see what heats up to see what exactly is shorted.

[ilikesteel]

Re: ELEMENT ELEFQ462 led/lcd power problem

Tom66,

well Tom first round went to the board. I tried as you suggested, but couldn't notice any one component defrost quicker than another. I even changed to the 1 ohm resistor. maybe I'm not doing it properly. does the part of the board I'm testing need to be covered in a snow like topping? is the shorted component really going to get warm enough quickly to show itself? I'm disappointed I didn't received the results I wanted.

What now, go for round two?

I searched for the main board all over the internet and didn't find any! looks like I may eat this one if I can't get better results.

thanks so much for your guidance, I know it's late in the UK. trade posts with you tomorrow.

frank

frank

[tom66]

Re: ELEMENT ELEFQ462 led/lcd power problem

It may be that if it is a really low ohm short, you need a higher current which a NiCad or NiMH cannot provide. If you can borrow a power supply with an adjustable current limit up to 3 amps, that could work.

[budm]

Re: ELEMENT ELEFQ462 led/lcd power problem

You try using this method. I use this for checking out short on new prototype PCB. It will help localize the location in that area.

[ilikesteel]

Re: ELEMENT ELEFQ462 led/lcd power problem

Tom66-budm,

Thanks for the response guys. I have a power supply but not sure about current limiting feature. I'll take a pic and maybe you can tell. the meter face on the PS has voltage reading on the bottom of scale and dc mill-amps on the top of the scale. the voltage can be dialed in.

budm,

can you explain your circuit a little more in depth, I'm going to need a just a bit more clarity, sorry. this is all brand new to me troubleshooting a circuit like this. thanks for you patience and understanding. I marked up your pic in red.

you guys are great, thanks again!

frank

[budm]

Re: ELEMENT ELEFQ462 led/lcd power problem

Just hook up the power supply to the two pad where the regulator was, then your meter in mV range, black probe right at the pad where negative of the power supply is connected to, then take the reading right at the pad where the positive of the power supply is connected to, take that reading, then start moving the red probe along the trace that is connected to the positive, you will see the voltage starting to drop as you get close to the short, the trace beyond the shorted will show the same voltage at the shorted point.
If you have any old circuit board around you can try it out by creating short and experiment with it to see how it works.

[ilikesteel]

Re: ELEMENT ELEFQ462 led/lcd power problem

Tom66-budm,

took a couple of pics of the power supply and my meter.

Tom, maybe the supply I have is a current limiting supply. I only used this supply for 12V for bench testing stuff. I don't have the manual. I'm sure it's many years old. if you can determine that it is from looking at it, just give me an idea how to use it in the way you want me too.

the knob on the right sets the meter for voltage or current. it also has another position called short circuit current. that part of the switch is spring loaded as it cannot be left on that position like the positions for V and I.

switch on left says short circuit current adjust. this may be a valid supply for this test.

budm,

a picture of my 802 fluke, goes to 200mv, is that worthy of your test method.


thanks a bunch,

frank

[tom66]

Re: ELEMENT ELEFQ462 led/lcd power problem

Should be usable, but it's only capable of around 750mA from looking at it?

[ilikesteel]

Re: ELEMENT ELEFQ462 led/lcd power problem

Tom66,

do you think that's too low and won't generate enough heat?

thanks
frank

[tom66]

Re: ELEMENT ELEFQ462 led/lcd power problem

Yeah, you tried up to 1 amp with no luck. I went for 3 amps in the video.