HP X20LED 20" LED not working

[angel-boy]

HP X20LED 20" LED , monitor does not work, no lights no power LED
i make some photos, hope you can help me.

model power bord 715g3598-m01-000-004s

[selldoor]

Re: HP X20LED 20" LED not working

Please post pictures of the Led Driver Board.
Is the mains adapter the original and if not is it the correct voltage and amps.
tested the output?
Is there a led on the adapter does it stay lit when plugged in.
The two orange caps have been replaced? - check soldering.
Is there any voltage showing on the caps when the adapter is plugged in.
If you unplug the lead to the panel (lvds) is there any voltage on caps.
If you un plug the lead to the led driver is there any voltage on caps

[lti]

Re: HP X20LED 20" LED not working

These monitors used a 12V 3A power supply, and those orange caps are most likely original. The HP x20LED monitor I looked at used the same orange caps.

I would also check the input and output voltages of the voltage regulators U704/U703 (1.8V) and U701/U702 (3.3V). It's strange that they gave each of those regulators two labels. There is also a switching voltage regulator controlled by U705 (MP1584). Measure its output voltage at the orange cap next to L701. I can't tell what its output voltage is supposed to be, but I'd guess that should be 5V.

[angel-boy]

Re: HP X20LED 20" LED not working

Hy , i edit the photo with the voltage , L701 coil produces a buzzing noise
The power LED lights blue , trying to turn ON and then OFF

[selldoor]

Re: HP X20LED 20" LED not working

Please post pictures of the Led Driver Board.
Is the mains adapter the original and if not is it the correct voltage and amps.
tested the output?
Is there a led on the adapter does it stay lit when plugged in.
The two orange caps have been replaced? - check soldering.
Is there any voltage showing on the caps when the adapter is plugged in.
If you unplug the lead to the panel (lvds) is there any voltage on caps.
If you un plug the lead to the led driver is there any voltage on caps

????

[angel-boy]

Re: HP X20LED 20" LED not working

with or without inverter connected, are the same symptoms, and is voltage on caps.
with or without ldvs LVDS connected, are the same symptoms, and is voltage on caps.
I tried with another power adapter , are the same symptoms
a capacitor is 5V, the other is 12V

[angel-boy]

Re: HP X20LED 20" LED not working

any help ?

[selldoor]

Re: HP X20LED 20" LED not working

I have asked twice for pictures of the led driver board ??

[angel-boy]

Re: HP X20LED 20" LED not working

I saw what you asked me, I did not picture because with module connected or not is not working.

I'll take a picture for you tomorrow.

[selldoor]

Re: HP X20LED 20" LED not working

Are there any voltages on any pins on the connector the led driver board plugs into.

[budm]

Re: HP X20LED 20" LED not working

Post 1 "HP X20LED 20" LED , monitor does not work, no lights no power LED"
Post 4 "Hy , i edit the photo with the voltage , L701 coil produces a buzzing noise
The power LED lights blue , trying to turn ON and then OFF"
I am confused, so the power LED is working then but no backlights? I sure like to see how all the boards are connected together.

[angel-boy]

Re: HP X20LED 20" LED not working

@budm

First time when i tested the monitor, no light on power led. i open the case, maybe there was weak contact.

No backlight, no image , like the monitor struggling to start , pulsing a few times, buzzing noise is heard on board, then restarts

[selldoor]

Re: HP X20LED 20" LED not working

Have you got an input - when you have can you see a very dark image of the input at any time - try with a flashlight shining on panel. Some monitors go into standby if no source.
I really think this is a led string/led driver problem, buzzing due to nothing using the voltage produced then no backlight, so goes into protection. ( I am often wrong with hunches though )

[budm]

Re: HP X20LED 20" LED not working

From looking at the board, lt looks like the U705 is the siwtching buck reulating IC driving the L701 to convert 12Vdc down to 5V, U702 convert 5V to 3.3V, the 3.3V is then converted to 1.8V by U704.
Is the processor with that black heatsing getting hot? It sounds to me that you may have bad filter caps (those orange caps) or the circuit is drawing too much current and causing the buzzing.

[angel-boy]

Re: HP X20LED 20" LED not working

Ok, i will change those orange caps, i will make photo with led driver, i will put vga input , i will light the display to see if appers something,

tomorrow make photo and upload here.

Thanks for help

[lti]

Re: HP X20LED 20" LED not working

The inputs of U701/U702 and U703/U704 are lower than I'd expect. I'd like to see the exact voltage readings at the orange cap next to L701 (C716?) and the outputs of the regulators (U701/U702 and U703/U704 only - don't worry about the voltage on each pin of U705).

By the way, it looks like the regulators are labeled twice because the board is designed for either SOT-223 or DPAK package regulators. That's why I include both labels.

[budm]

Re: HP X20LED 20" LED not working

The input to the regulators may be fed through the blocking diode thus about 0.6V lower than 5V and 3.3V. It can easily be verified by check the 5V output to the input pin to see if it has direct connection, same for the 1.8V regulator, see if the input of the 1.8V reg is directly connected to the 3.3V out of the 3.3V reg. IC

[angel-boy]

Re: HP X20LED 20" LED not working

i change the 480/10 with 480/16v, and 180/16v, with 220/16v, i make measurements,i have attached pictures of voltage changes

U101 i read atmlh 010-02b
i see that C713 is pulled on board see photo.

with inverter, display connector or without them , the voltage is the same , and oscillates as in pictures

Already I feel stressed about it.

[budm]

Re: HP X20LED 20" LED not working

https://www.badcaps.net/forum/attach...9&d=1422003788
OK, so it looks like you are getting the BL_ON signal (light on 3.12V) and the 12VDC feeding the backlight LED driver board.
https://www.badcaps.net/forum/attach...0&d=1422004034 so now you need to find out if you are getting the boosted Voltage on that brown filter cap close to the LED connector. It is rated at 100VDC so I expect more than 50VDC on that cap. The Yellow and the Green cables on the LED driver board are for the BL_ON and the Dimming Control signals.

[lti]

Re: HP X20LED 20" LED not working

The input to the regulators may be fed through the blocking diode thus about 0.6V lower than 5V and 3.3V. It can easily be verified by check the 5V output to the input pin to see if it has direct connection, same for the 1.8V regulator, see if the input of the 1.8V reg is directly connected to the 3.3V out of the 3.3V reg. IC

I see the diodes on the bottom of the board now. I don't think I paid much attention to the bottom of the board when I had this monitor open. I took pictures of the top of the main board and T-Con, so I don't have any pictures to refer to for the LED driver. It definitely sounds like the backlight isn't working.

In the monitor I looked at, U101 was a 24C02 EEPROM. U402 was a 25L2026D. One of those is the main firmware ROM, and the other is the EDID ROM.

The 0.08V reading on CN701 might be a problem. That pin is connected to the green wire on the cable to the LED driver. I guess it could be the brightness control pin and 0V indicates minimum brightness. I never checked because the backlight in the monitor above was working. The missing cap could also be the problem. The part number on U801 on the LED driver might help.