low voltage regulator

[Salvamex]

I have a Vizio M3D550KDE that has jumping pictures and lines.
I read the section on how to test the low voltage regulators.
I tested the ones with the dash prefixes (it says that the - prefixes means that it's a fixed regulator) but I can not find the data sheet for the following one that is not fixed and not sure which is the part number:

0273
912t43

That is exactly how it looks on top of it.
is it 0273 or 912t43 or all together?

I looked for it at the following link already but I can not find it.

http://pdf1.alldatasheet.com/datashe...C/1117-33.html

Please help.

Thanks

[tw2005]

Re: low voltage regulator

G912T43

positive 1.2V voltage regulator,1A output current. TO252 package

Take particular note of suffixes 43, 45 as the pinouts are different if looking for a substitute.

[Salvamex]

Re: low voltage regulator

Thanks for the help.
Where did you get that information?
I will need to test others and I would hate to be bothering you every time.

Thanks again.

[Salvamex]

Re: low voltage regulator

is there any link on this forum to go to about learning how to read the markings/stampings of the low voltage regulators.
By the markings or stampings I mean the letters and numbers on top of the ldo.

[Salvamex]

Re: low voltage regulator

Take a look at these pictures and tell me if these are low voltage regulators.
I looked up the markings on them and they come up us HIGH VOLTAGE SCHOTTKY RECTIFIER.
is that the same as a low voltage regulator or not?
If not can some one tell me how to test if they are good.
The readings are in the 133 volts but i do not know if I am testing them properly.
Please help.
Thanks

[mariushm]

Re: low voltage regulator

The D201 and D482 tell you those are DIODES.
D is diode, ZD is zener diode, C is capacitor, R is resistor, L is inductor, F is fuse.
ICs and mosfets usually get the letter Q

So yes, those should be rectifier diodes, schottky rectifiers. Search for the datasheet for those, see which pins are the cathode, which is/are the anode then put your multimeter on DIODE check and test it.

For example, for that SDB51.. you have datasheet here: http://pdf1.alldatasheet.com/datashe.../SDB5150D.html

In the pdf you see that pins 1 and 3 are the anode and center pin and the tab are cathode. If the diode is OK, with your multimeter on diode check you should get a reading if you measure from anode (any of the 2 pins) to cathode (the tab or center pin) and you should see the voltage drop, (let's say 0.15v or 150 on your meter) and if you reverse the leads you shouldn't get anything and the metter should say OL or open (open circuit, diode blocks the electricity flow)

If the meter beeps and/or shows 0, that means the diode is short circuited, faulty.

See this video if it's still not clear: https://www.youtube.com/watch?v=JlZtn2PTuYo

[Salvamex]

Re: low voltage regulator

Thanks for information.
I will test to see if they are any good.

[Salvamex]

Re: low voltage regulator

Well I tested the SDB51 and they are good.
When you look at the markings on a low voltage regulator or a schottky rectifier (they both look the same to me) which is the number that I go by, the bottom number, the top or both?

I have tried all of them and I can not find any data sheets on the d482.
is there a video that teaches this?

I know I might sound dumb, but I am new and want to learn so please be patient and thanks for the help.

[mariushm]

Re: low voltage regulator

Normally I would search for subsets of the name, i would search for BA2S13 or BA2513, then search for "BA2" and see what pops up. You know the package is to-252 or dpak or something like that so you can further filter out.

I would also try to make some educated guesses... for example with SDB5150D you can tell it's 5A , 150v (therefore 5150 in the name) but with this second one it's trickier because 13 or 130v is not a standard voltage (usually these diodes are using multiples of 50 or 100v)
Same with 482 .. can't say it's 4A 82v .. could be 8 x 10^2 = 800v but I doubt it.

But anyway, it's a basic diode, who cares about datasheet? As long as it has a voltage drop in one direction and none on the other other, it's a functioning diode.

[Salvamex]

Re: low voltage regulator

Thank You for the information, but don't you need to know which is the anode and cathode??
That is why you need the spec sheet right?

[mariushm]

Re: low voltage regulator

Components like diodes only have anode and cathode. They're pretty much standardized parts, so it makes little sense for this unknown chip to have the leads in another order compared to that other diode.

How I would do with that part.

The other diode has pins 1 and 3 anode, pin 2 (unsoldered) and tab cathode. I don't have any reason to believe this diode is different, but I can check.

Put meter on continuity.
Is pin 1 and pin 3 (the soldered small ones) shorted together? If yes, then it means those two are BOTH either cathode or anode.
Is pin 2 (unsoldered one) and tab shorted together? If yes, then it means those two are shorted together, so BOTH are either cathode or anode.

If not, then check which ones are shorted together. You basically separate the pins into two groups : cathodes and anodes.

A diode is like this ----- anode ---- [===]>| --- cathode---

Put meter on diode check. Red probe on anode and Black probe on cathode should result in showing you on screen the voltage drop on the diode. The other way around, it should show open circuit (OL is often displayed).
If you get in either directions a beep or error message from multimeter or something super close to 0, it means the diode is shorted (or you're not actually measuring a diode)

So just put probes either way and as soon as you get a reading that makes sense (for example 0.15v or 0.4v you know the tab or pin under the red probe is your anode.

Problem solved.

Now it would be a bit trickier to determine how much current the diode can handle and what's the breakdown voltage, but again you can pretty much figure that out from the package and from the circuit.
That othe diode has a breakdown voltage of 150v and it's rated for 5A. if this diode was 1-2 amps, they would have probably used diodes in smaller packages, so this diode must be rated for at least 2-3 amps.
Looking at the circuit, you can see that the tab of diode is on a large copper trace, which then goes into those inductors and then the current from the inductors goes towards the connector at the bottom (the red wires)... and you see there a capacitor rated for 35v max. So the voltage on the large trace that touches the diode should be under 35v but diodes' breakdown voltage is recommended to be at least 40-50% above the voltage touching the diode... so the diode should be rated for at least 80-100v.

So I'm looking for a 2a+ , 80-100v+ diode in to-252/dpak/etc diode.

Now let's say I measured 0.15v voltage drop using the multimeter. However, this is at very low current and this voltage drop will change when higher current flows through it.

So i'd desolder the diode, get a 12v lightbulb (10-20w) and put the diode in series with that lightbulb and a 12v power supply.
12v is pretty much a low voltage that's unlikely to break the diode, and the 10-20w is only about 1-1.5A which the diode should handle for a few seconds. Turn the circuit on, measure voltage drop using the multimeter when 1A+ goes through it. Let's say I get 0.3v at 1A voltage drop.

So now I can go on Digikey and search for some diodes in that package with the max current and max voltage I assume and I can look in the datasheets of those diodes and pick a diode that will have a graph for that voltage drop on diode which has about 0.15v at 0A and about 0.3v at 1A. That part will be good enough.

[budm]

Re: low voltage regulator

Those two devices you have marked them as D482, is that the number as printed on the body? I can tell right now that they are not Diode. I see one pin has the typical Resistor/diode network which are used for the Gate drive.
That board is also the LED driver board which its purpose is the generate backlights so you can see image on the screen, it will not cause the pictures to jump or causes the line on the screen, that sound more like the screen, T-CON problem. Backlights circuit cannot make lines on the screen.
http://www.shopjimmy.com/lg-6917l-0083a-led-driver.htm

[Tvbob]

Re: low voltage regulator

I Concur with Budm. You can often find out more about a unknown part, By looking at the associated components.