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Old 12-09-2014, 10:52 AM   #1
wash
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Default HP ZR2740w almost dead

Hallo, i have a big problem with my monitor.
I'll try to explain the problem with my poor english ...


Now, is out of warranty and is unusable

after a while the monitor goes off, and when i click the power button to power on again, i see the image for a second, as a flash, then it goes black again, i click the power button, another flash, then black, and so on...

i've seen is a common problem with this monitor, is the worst made monitor i've ever seen, and it was a 800 monitor, thank you hp.

i've had this problem this summer, but after some week the problem disappeared, but now the problem is again here and i have not warranty anymore (i had to use warranty months ago...my bad)


do you think is possible to repair it?
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Old 12-09-2014, 03:16 PM   #2
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Default Re: HP ZR2740w almost dead

i've dismounted the monitor and i don't see anything wrong, nothing burned, all caps seems ok...
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Old 12-09-2014, 03:36 PM   #3
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Default Re: HP ZR2740w almost dead

the symptom is called "2 seconds to black". Read the sticky for starters.
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Old 12-09-2014, 03:46 PM   #4
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Default Re: HP ZR2740w almost dead

Quote:
Originally Posted by CapLeaker View Post
the symptom is called "2 seconds to black". Read the sticky for starters.
so can i post the photos and do you think you could help me?

(i have a multimeter, soldering stuff and so on)

thank you...
Attached Images
File Type: jpg P1000495.JPG (604.2 KB, 184 views)
File Type: jpg P1000496.JPG (575.5 KB, 110 views)
File Type: jpg P1000497.JPG (577.5 KB, 79 views)
File Type: jpg P1000498.JPG (784.9 KB, 80 views)
File Type: jpg P1000499.JPG (787.8 KB, 67 views)

Last edited by wash; 12-09-2014 at 03:57 PM..
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Old 12-09-2014, 04:14 PM   #5
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Default Re: HP ZR2740w almost dead

wash,

I'd first check all of the voltages on the P803 and the P804 against their respective silkscreens.
If they are present then your power supply (pic 1 and 2) is working fine.

Next I'd move over to the inverter board (not shown in your pix).

Last edited by HAHOMETP; 12-09-2014 at 05:13 PM..
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Old 12-09-2014, 04:27 PM   #6
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Default Re: HP ZR2740w almost dead

Quote:
Originally Posted by HAHOMETP View Post
wash,

I'd first check all voltages on P803 and P804 against their respective silkscreens.
If they are there then your power supply (pic 1 and 2 from left) is working fine.

Next I'd move over to the inverter board (not shown in your pix).
do you see p803 and 4 in the photo? i see only p802 on the left-center

Quote:
Originally Posted by HAHOMETP View Post

Next I'd move over to the inverter board (not shown in your pix).
do you mean this? (attachment)
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File Type: jpg P1000494.JPG (607.5 KB, 92 views)

Last edited by wash; 12-09-2014 at 04:43 PM..
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Old 12-09-2014, 05:12 PM   #7
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Default Re: HP ZR2740w almost dead

You are probably looking at the jumper J802.

P803 and P804 are the headers in the upper and lower right corners of the 1st picture.

The picture in your last post is of the T-Con board. What you need is the inverter board driving the backlight. This board will have several high voltage transformers on it.
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Old 12-09-2014, 05:23 PM   #8
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Default Re: HP ZR2740w almost dead

Quote:
Originally Posted by HAHOMETP View Post
P803 and P804 are the headers in the upper and lower right corners of the 1st picture.
i'm sorry but...i don't understand what do you mean....

where exactly?
Attached Images
File Type: jpg P1000500.JPG (522.4 KB, 53 views)
File Type: jpg P1000501.JPG (502.1 KB, 40 views)

Last edited by wash; 12-09-2014 at 05:27 PM..
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Old 12-09-2014, 05:49 PM   #9
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Default Re: HP ZR2740w almost dead

This is LED backlights LCD panel, no high voltage inverter board, it has power supply/LED Driver board combination.
P804 connector goes to the LED stings (looks like it has 4 strings, VD1~VD4) inside the LCD panel.
So check the DC Voltages on P803 which has the labels for each pin, report the readings with the name of each pin also.
More likely to have one or more string with open LED so it goes into protection shutdown, or the wires to the LED assemblies shorted to the chassis.
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Basic LCD TV and Monitor troubleshooting guides.
http://www.badcaps.net/forum/showthr...956#post305956

Voltage Regulator (LDO) testing:
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Inverter testing using old CFL:
http://www.badcaps.net/forum/showthr...er+testing+cfl

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Last edited by budm; 12-09-2014 at 05:55 PM..
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Old 12-10-2014, 04:57 AM   #10
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Default Re: HP ZR2740w almost dead

A test of the backlight in the lcd is on order. Doesn't matter if ccfl or led. The constant current led driver board is shutting down for a reason.
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Old 12-10-2014, 01:47 PM   #11
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Default Re: HP ZR2740w almost dead

the p803 give 5v on all the 5v pins, nothing in the 12v pins (pin6-7) and 2v on pin 3, 3v on pin 2 and 4v on pin 1


on P804 it gives 0.2 v on all pins (vo1, vo2, vo3 etc)
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Old 12-10-2014, 01:59 PM   #12
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Default Re: HP ZR2740w almost dead

So pin 2 ON/OFF (BL ON) = 3VDC
Pin 3 PS ON = 2VDC
The main board is sending the correct signal to turn on the power supply.
Now we need to find out of the PFC Voltage booster circuit is working or not, you will have to measure the DC Voltage right at the two legs of the main filter caps (two large caps laying on their sides), it should have > 360VDC on the legs.
I also need good straight shot pictures of the bottom side of this power supply board.

Last edited by budm; 12-10-2014 at 02:00 PM..
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Old 12-10-2014, 02:14 PM   #13
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Default Re: HP ZR2740w almost dead

Quote:
Originally Posted by budm View Post
So pin 2 ON/OFF (BL ON) = 3VDC
Pin 3 PS ON = 2VDC
The main board is sending the correct signal to turn on the power supply.
Now we need to find out of the PFC Voltage booster circuit is working or not, you will have to measure the DC Voltage right at the two legs of the main filter caps (two large caps laying on their sides), it should have > 360VDC on the legs.
I also need good straight shot pictures of the bottom side of this power supply board.
where i have to put the ground of the multimeter? if i put the red cable on the + of the capacitor and the black (ground) in the negative, i have something more than 150v, (they are 250v caps 220uF)


Quote:
Originally Posted by budm View Post
I also need good straight shot pictures of the bottom side of this power supply board.
this picture is ok?
Attached Images
File Type: jpg P1000507.jpg (1.11 MB, 125 views)

Last edited by wash; 12-10-2014 at 02:44 PM..
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Old 12-10-2014, 03:10 PM   #14
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Default Re: HP ZR2740w almost dead

OK, those two filter caps are connected in series to handle high voltage, so red probe on the + of C802, Black probe on the - of C807.
BTW, looking at the bottom of the board now I see that it has 6 strings of LEDs.

Last edited by budm; 12-10-2014 at 03:11 PM.. Reason: i
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Old 12-10-2014, 04:08 PM   #15
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Default Re: HP ZR2740w almost dead

Quote:
Originally Posted by budm View Post
OK, those two filter caps are connected in series to handle high voltage, so red probe on the + of C802, Black probe on the - of C807.
around 320 -330v.

Last edited by wash; 12-10-2014 at 04:17 PM..
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Old 12-10-2014, 04:45 PM   #16
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Default Re: HP ZR2740w almost dead

Is that when the power switch is activated (PS_ON goes HIGH)?
The PFC Voltage booster should boost the Voltage from around 325V (230 ac line x 1.414 = 325V) to >360VDC which is required by LED driver circuit to function.
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File Type: jpg POWER BLOCKS.jpg (2.13 MB, 68 views)

Last edited by budm; 12-10-2014 at 04:52 PM..
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Old 12-10-2014, 04:56 PM   #17
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Default Re: HP ZR2740w almost dead

Quote:
Originally Posted by budm View Post
Is that when the power switch is activated (PS_ON goes HIGH)?
The PFC Voltage booster should boost the Voltage from around 325V (230 ac line x 1.414 = 325V) to >360VDC which is required by LED driver circuit to function.
i start with the monitor off (linked to ac and to pc)

it's around 320

then i click the ON button, the blu led goes on, the voltage go to around 400-410v, (the monitor flash the pc image as usual) then it drops after 2 second to 320v.

Last edited by wash; 12-10-2014 at 04:59 PM..
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Old 12-10-2014, 05:09 PM   #18
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Default Re: HP ZR2740w almost dead

Can you check the PS_ON pin to see if it did go up close to 5V or it stays at 2V after the power switch is activated?
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Old 12-10-2014, 05:13 PM   #19
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Default Re: HP ZR2740w almost dead

Quote:
Originally Posted by budm View Post
Can you check the PS_ON pin to see if it did go up close to 5V or it stays at 2V after the power switch is activated?
remains at 1.8v
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Old 12-10-2014, 05:19 PM   #20
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Default Re: HP ZR2740w almost dead

OK, we have to try this, we need to force on the PS_ON pin by using 100~1K resistor between the PS_ON pin and the 5VSTBY pin, BUT YOU HAVE TO make sure to disconnect the PS_ON wire that goes to the main board first.
Then we will see if the boosted Voltage will stay on @400VDC, if it does not then we will have to do more in-depth troubleshooting of the power supply board.

Last edited by budm; 12-10-2014 at 05:20 PM..
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