Philips LED 226V3L no sign of life, wont power on, no led

[BadCon]

Hi, I'm new on this forums and I've already fixed several LCDs, PSUs and MBOs replacing bad capacitors. But, I'm unable to fix this LED screen by myself.

LED monitor is Philips model 226V3L, with AU Optronics M215HW03 V1 panel.
No sign of life after connecting to mains. Worked flawlessly, one day just wont power on.

Power supply board is 715g4497-p03, no bulging caps.
connectors on it are CN804 6pin which goes to LED panel (probably backlight);
and CN902 which connects to control mainboard, pins: DIM, ON/OFF, GND, GND, 5V, 5V, VOL, MUTE. Just to notice, screen doesnt have speakers.

Control mainboard is 715G4401-M03 with Novatek NT68660UFG MCU.
Google show that is ViewSonic board, so probably Philips used ViewSonic LED screen controller?
connectors on it are CN701 which connects to power supply board CN902;
and CN404 which connects to 715G4921-K02 key board switch which have power button and power LED.


I have basic multimeter, and first thing I do was checked voltages.
It seems that only 5V is going to control mainboard, checked that rail and it's rock-stable at 5.02VDC.
I also tested the wiring of switch keyboard pcb, seems OK.

Considering U401 Novatek IC and R707 4.7Omh resistors are getting warm when power is plugged in, I'm assuming control mainboard is dead?
I don't think it's normal for that components to get hot, especially when screen is not powered on and it's "green energy, low-consumption standby model"... Is there any chance of fixing it? With your help, I can test components on control mainboard, find replacement and resolder it.

Pictures of power supply and control mainboard are in attachment. If needed, I can take more pictures, just say.

Thanks in advance for every suggestion.

[budm]

Re: Philips LED 226V3L no sign of life, wont power on, no led

What are the DCV reading on all 3 legs (with ref to gnd) of those two Voltage regulator ICs on that main board?
And what are the DCV on that white connector of the power supply board that goes to the main board? It looks like the pins are label so make sure to report the pin name and follow by the DCV reading.

[BadCon]

Re: Philips LED 226V3L no sign of life, wont power on, no led

Thanks for the reply. I already wrote DVC reading of white PSU connector, here are detailed measurements I made now:

Without main control board connected:
DIM, N/P, ON/OFF, GND, VOL, MUTE reads 0VDC
5V reads 5.14VDC (thats without load/main board connected).

With main board connected to power board:
DIM reads 80mVDC
ON/OFF reads 85mVDC
N/P, GND, GND, VOL, MUTE reads 0VDC
5V reads 5.04VDC

Upper voltage regulator is GH12D 1.8V:
Input connected through big R707 4.7Ohm resistor to 5V rail.
Vin is 1.93VDC at start then slowly dropping.
Vout is 1.42VDC at start, then dropping.

Lower voltage regulator is GH12E 3.3V.
Input connected directly to 5V rail.
Vin is 5.02VDC
Vout starts at 3.32VDC then dropping.

[budm]

Re: Philips LED 226V3L no sign of life, wont power on, no led

"Upper voltage regulator is GH12D 1.8V:
Input connected through big R707 4.7Ohm resistor to 5V rail.
Vin is 1.93VDC at start then slowly dropping.
Vout is 1.42VDC at start, then dropping."

You have problem there in that section, that is 1.8V Fixed regulator. the input is too low for it to get 1.8Vout, I believe (need to look at the spec sheet) the input to Regulator needs to be 2V above the required output.
I would check the resistance between GND and Input pin, GND and output pin.

[BadCon]

Re: Philips LED 226V3L no sign of life, wont power on, no led

I though problem was in MCU, which drives excessive current and therefore drops voltage of regulator (as MCU gets really hot together with R707 4.7Ohm resistor which is in series with input of 1.8Vreg), but it was not the problem.

Checked resistance as sugested, seems almost identical for two Vregs.
Maximum input voltage for Vreg is 6V, minimum is 2.0V, so it should work at 1.93VDC i measure before.
I also tried to short out 4.7Omh resistor which is connected in serial with Vin of Vreg and 5V rail, so Vreg was connected directly to 5V, still same thing and same 1.4VDC output.

Then I desoldered AP2114H GH12D 1.8V vreg, and just for testing purposes I put LM317 set for 1.8V, monitor is back alive and works beautifully. Tested VGA input, works fine. Measuring 1.8V current draw from LM317 output, is about 60mA. In attachment are pics of alived monitor together with picture of LM317 test-setup for 1.8V rail. Thanks budm for finding this one.

As soldering LM317 in TO-220 package will all its additional components (resistors, caps, diode) and setting it to output 1.8V is a bit dodgy, I started to look for SOT223 replacement for GH12D-1.8V 1A (which is not available to me).
I found LM1117 which is 1.8V 800mA SOT223 Vin max 20V, pinout is the same. I assume it will fit as substitute and work without problem? If so, I'll buy it tomorrow, solder it and hopefully everything will work so I can put monitor all back together.

So, can I use LM1117 1.8V as substitute for AP2114H GH12D 1.8V? Both are in the same SOT-223 package with same pinout, and same Vout. LM1117 seems to have a bit lower output current rating (800mA instead of 1A), and maximum input voltage of 20V instead 6V on G12D.

[budm]

Re: Philips LED 226V3L no sign of life, wont power on, no led

You may get away with 800mA but we do not know how much current the load, but you can find that out by measuring the Vdrops on that 4.7 Ohms resistor that feed the Vin of the IC then you can calculate the current.
I am glad you found the problem, but you need to understand about the Linear Voltage regulator IC.
'Maximum input voltage for Vreg is 6V, minimum is 2.0V, so it should work at 1.93VDC i measure before." You only feeding it with 1.93 and trying get regulated 1.8V out, that means the Vrops on the regulator will be only 0.13, that is not enough different Between Vin and Vout, if you look at the spec of the IC you will understand it better.
Drop out spec for 1.8V vreg is 0.50V TYP (or up to 0.70V), that means the input has to be at least 1.8 + 0.5v = 2.3V Vin. (or 1.8 + 0.7= 2.5V)

https://cdn.badcaps-static.com/pdfs/...82726d558e.pdf
https://cdn.badcaps-static.com/pdfs/...6e558f9da2.pdf

[BadCon]

Re: Philips LED 226V3L no sign of life, wont power on, no led

Big 4.7Ohm is connected in serial with input of 1.8Vreg, to 5V rail. I already tried to short out that resistor, no luck. Why is that resistor there, if you can learn me something? If AP2114 max is 6V, and circuit consumes just 60mA, there wont be that much of power dissipated in voltage regulator.

As i stated above, for testing purpose I connected LM317 directly to 5V input (avoiding that resistor) and measuring the 1.8V output current from LM317 regulator. Measurements says about 60mA. Not even near 800mA.

Immediately after you sugest me to measure voltage regulators, I download datasheet for it to check it's nomiral output voltages. Me too found 2V input suspicious, so i searched for minimum input voltage and found a graph (graph attached below) which says at 2.0V input voltage, output will be 1.8V. You're right, I forgot to look at Vdrop, which 0.5V/0.7V max as you stated. I suspect there was only 2V at input because resistor got too hot, same for Novatek MCU. Im glad that MCU survived.

While testing with LM317, I found out that without load its output voltage is 1.78V and when I turn monitor ON, it drops to 1.56V, but everything works just fine, output draws 62mA. Voltage drop is probably because a lot of long thin dodgy crocodile cables to temporary connect LM317 and its resistors as 1.8Vreg? Notice I wasn't using any resistors with LM317 for this quick-test if screen wil work with 1.8V.

Althrough I can solder LM317 and make it permanent "fix" for 1.8V rail, it will consume lot of unecessary space and be dodgy. Thats the reason why im looking for SOT223 supstitute for AP2114. My question is, can I place LM1117 1.8V reg instead of AP2114, and should it work like new? That way, I just replaced bad component and no other mods or touching on PCB other than that.

[budm]

Re: Philips LED 226V3L no sign of life, wont power on, no led

I found out that without load its output voltage is 1.78V and when I turn monitor ON, it drops to 1.56V," that is not good, if the load is only 60mA it should not drop down like that.
The load regulation of that the AP2114 is"Excellent Load Regulation: 0.2%A (Typ) @
IOUT=1mA to 1A " from spec, so your 317 is not regulating since.
Vdrops out for 317 is between 1.75V ~2V or so.
The 4.7 Ohms helps reduce power dissipation of the 2114.
If 5V is fed directly to 1.8V reg, the Voltage drops on the IC will be 3.2V, multiply that by 100mA = 0.32W.
So for you to use 317, you need to bypass the 4.7 Ohms resistor and see if it can still maintain 1.8V

[BadCon]

Re: Philips LED 226V3L no sign of life, wont power on, no led

I bypassed 4.7Ohm resistor and connect LM317 directly to 5V rail.
Vin is 5.10V
Vout when screen standby 1.80V
Vout when screen turned on 1.56V

Current from 5V rail to LM317 Vin = 152mA
Current from LM317 Vout screen in standby = 1.1mA
Current from LM317 Vout screen turned on = 62mA

Also I try to connect LM317 through 4.7Omh resistor, output voltages are the same, but input voltage is 4.41V (5.10-4.41V is 69mV voltage drop through resistor).

I made few tests about voltage dropping with LM317. Tried changing resistors, etc, but with load (30ohm resistor), voltage drops significantly. Searched around the web, I'm not alone, can be a problem with missing filtering caps, or resistor values (althrough I used variuos values).

I don't want to use LM317 as fix for this, because it's not proper repair (putting to220 element with few more resistors and caps instead of single sot223). But if I need, I can use LM317 and be happy it works.

If unit really consumes jsut 60mA and 1.8Vreg is connected to 5V rail, I dont think a seperate 4.7Ohm resistor is needed to help reducing power dissipation. Im suspicuos maybe it should take more current. But, It works and takes just 60mA, thats why Im now confused.


Now, one thing on my mind. If unit works at 1.56V, maybe unit wont work at 1.8V? Maybe 1.8Vreg wasnt bad? I cant test it because I damage it when desoldering. Is that mean that if I solder 1.8V reg, unit can be dead again, taking too much current and overheating both 4.7Ohm resistor and MCU?


Sorry about messy post, its late here, I'll buy LM1117 1.8V Vreg, solder it, test if monitor works and measure Vdrop on 4.7Ohm resistor and output voltage of LM1117. Fingers crossed everything will be okay!
If anybody have any other suggestion, feel free to say before magical smoke escapes...

[budm]

Re: Philips LED 226V3L no sign of life, wont power on, no led

I am surprise that the board still working properly with 10% less Voltage and with such low current, may it need to be in certain operating condition that you may not aware of, and for them to use regulator with such tight regulation of 0.2%. They must have chosen that for reason.

[BadCon]

Re: Philips LED 226V3L no sign of life, wont power on, no led

Im glad it worked at just under 1.6V, because if its not I would suspect circuit takes too much current so Vreg protection kicks in and lower the voltage.
For 0.2% regulation, I dont know. Im not that good, but i hope 0.4% will be enough good for operation.

I just purchased LD1117 1.8V SOT223 today. Datasheet says its max load regulation is 0.4% and line regulation 0.2%.
First I connected it with crocodile test wires, output voltage drops exactly as with LM317, but unit works.
I go ahead and soldered it into place (pic attached). Now, voltage is stable even in loaded condition.
So vdrop must be because thin crocodile clip wires or in combination with lack of filtering caps near Vreg.

Everything works fine, Im happy, and nothing heats up. Vdrop across 4.7Ohm resistor is just above 1V.
Monitor fixed and closed, problem solved. Thanks again, budm. Hope you can help me next time I got stuck like this time, hehe

[Davi.p]

Re: Philips LED 226V3L no sign of life, wont power on, no led

Hi,
"So vdrop must be because thin crocodile clip wires or in combination with lack of filtering caps near Vreg."
I think the second..
"Monitor fixed and closed, problem solved. "
I suspect that fault came from surrounding electrolitic caps.. or the power b'd caps, sadly you closed the cover..
for the compatilbility i remember something with very similar marking i saw on a LG tv, in the schematics it was marked 1117 so i think is a replacement.

[budm]

Re: Philips LED 226V3L no sign of life, wont power on, no led

I wonder if it is oscillating, so replacing the input cap and output caps may be required unless you have the scope to look at output and the input.

[BadCon]

Re: Philips LED 226V3L no sign of life, wont power on, no led

I suspect that fault came from surrounding electrolitic caps.. or the power b'd caps, sadly you closed the cover..

I was looking to replace power board electrolitic caps too, but as their values for Low ESR versions isn't available in local store, I just closed it as I dont want to order, paying shipping, and wait for caps from online stores outside country. I doubt that 10mF (or so) electrolitics caps can be problem in control board. Monitor is LED so doesnt get hot and dont have much power on hours so I think caps in power supply will be fine for workhours to come.

I wonder if it is oscillating, so replacing the input cap and output caps may be required unless you have the scope to look at output and the input.

Oscillating what? As i said earlier, after soldering LD1117 1.8V, output voltage is 1.78V and stable at load. Input/output caps of Vreg are present, and are default part of control mainboard circuit. I don't have access to scope or know how to use it.


BTW, is there way to check power on hours time information? I dont seem to find that info in factory hidden menu.

[budm]

Re: Philips LED 226V3L no sign of life, wont power on, no led

It is oscillating when you have the IC connected with long wires which you cannot see that with your meter, you have to look at with the scope.

[Davi.p]

Re: Philips LED 226V3L no sign of life, wont power on, no led

BadCon if you have difficulties to find capacitors is one count, but if you don't and you don't have scope/esr meter is often a good solution to change surrounding caps if you want the thing will last long, anyway nowadays on ebay there are plenty ESR-cap-ohm-volt meter all in one at ridicolous costs.. listen to the papa (as we say ) ..