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Old 12-11-2014, 05:03 PM   #41
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Default Re: HP ZR2740w almost dead

I would remove all the resistors except the one for the PS_ON and put everything back together again and see if you can still see the screen flashes on with an image for seconds.
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Old 12-11-2014, 05:29 PM   #42
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Default Re: HP ZR2740w almost dead

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Originally Posted by budm View Post
I would remove all the resistors except the one for the PS_ON and put everything back together again and see if you can still see the screen flashes on with an image for seconds.
yes i see the flash

i had to test the vo1 vo2...with the resistor? i removed it before testing.

now i test again.

thank you.
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Old 12-11-2014, 06:25 PM   #43
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Default Re: HP ZR2740w almost dead

You will have to remove the resistors that we put on the ON/OFF pin and the VADJ pin, and put those two wires back in place but we still want to leave the resistor between the PS_ON and +5V in place (because we still need this resistor for the PFC to work) and the PS_ON wire still disconnected, then have all the boards connected back together, then put the meter probes on the GND and VO1, then apply the power to the monitor and record the Voltage reading of VO1, then remove the power and then put the probe on VO2, apply the power and record the reading, then do the same thing again on VO3~VO6.

Last edited by budm; 12-11-2014 at 06:28 PM..
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Old 12-11-2014, 07:06 PM   #44
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Default Re: HP ZR2740w almost dead

ok
with BOTH the resistor i get something around 30V that slowly drops, BUT with the ground of the multimeter on VO1 and the red one on the GND

if i use the red wire with the positive and the black on the gnd (as it should be used) the indicator goes below 0......

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You will have to remove the resistors that we put on the ON/OFF pin and the VADJ pin,
i never put a resistor on the vadj pin....there is a misunderstanding somewhere...

pin2 ---resistor---5v
pin3----resistor---5v

now you are talking about a resistor on the pin1 (vadj) .......
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Old 12-11-2014, 08:18 PM   #45
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Default Re: HP ZR2740w almost dead

OK, leave pin 2 and 3 as is for now then. Black is for negative so put that on the GND pin, Red is positive so put that on VO1 and check the reading, unplug the monitor and then move the red probe to VO2 and the black probe on the next GND, apply power to the monitor and take the reading, repeat the same test on VO3~VO6.
I am looking to see if all the VO's have the same reading every time the power is applied to the monitor, it is important that you remove the power and then apply the power when you test each VO output.
I think you should also read the meter user manual.
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Old 12-12-2014, 11:26 AM   #46
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Default Re: HP ZR2740w almost dead

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OK, leave pin 2 and 3 as is for now then. Black is for negative so put that on the GND pin, Red is positive so put that on VO1 and check the reading, unplug the monitor and then move the red probe to VO2 and the black probe on the next GND, apply power to the monitor and take the reading, repeat the same test on VO3~VO6.
I am looking to see if all the VO's have the same reading every time the power is applied to the monitor, it is important that you remove the power and then apply the power when you test each VO output.
I think you should also read the meter user manual.
i did, but if i put the red one on vo1 and the black on the gnd, i get negative results. if i invert the multimiter wire, i get something around 30 that slowly decrease...

.
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File Type: jpg attachment.jpg (335.4 KB, 86 views)
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Old 12-12-2014, 11:58 AM   #47
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Default Re: HP ZR2740w almost dead

OK, I look at the bottom side of the board, the VO are negative outputs that is why you had to connect the meter that way, all the GND pins of connector P804 are tied together and connected to the circuit ground and the chassis.
Then do the same reading on the rest of the VOs, we need to find out if all the VO is putting out 30V, the one with open LED will have higher Voltage.
" i get something around 30 that slowly decrease" That is because the circuit goes into shutdown.
BTW, you should get good digital meter.
I need the readings of ALL SIX VO.

Last edited by budm; 12-12-2014 at 12:09 PM..
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Old 12-12-2014, 12:27 PM   #48
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Default Re: HP ZR2740w almost dead

This is what I come up with based on the pictures you provided.
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Old 12-12-2014, 01:44 PM   #49
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Default Re: HP ZR2740w almost dead

Quote:
Originally Posted by budm View Post
This is what I come up with based on the pictures you provided.
vo1 30
vo2 30
vo3 30
vo4 60
vo5 30
vo6 30

and all of them slowly drops....
(when i say 30, in fact it's around 28-29)

Last edited by wash; 12-12-2014 at 02:04 PM..
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Old 12-12-2014, 02:31 PM   #50
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Default Re: HP ZR2740w almost dead

Well, the LED string attached to VO4 is the suspect, the Voltage will be higher than the other outputs due to no load connected, open LED or open wire to the LED string, but more likely to be open circuit LED.
So you will have to disassemble the panel and test the LED, not going to be easy and you will have to remove the old LED and install a new one or may be able to bypass the bad LED.
It looks like each string has 9~10 LEDs.

Last edited by budm; 12-12-2014 at 02:32 PM..
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Old 12-12-2014, 02:34 PM   #51
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Default Re: HP ZR2740w almost dead

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Originally Posted by budm View Post
Well, the LED string attached to VO4 is the suspect, the Voltage will be higher than the other outputs due to no load connected, open LED or open wire to the LED string, but more likely to be open circuit LED.
So you will have to disassemble the panel and test the LED, not going to be easy and you will have to remove the old LED and install a new one or may be able to bypass the bad LED.
It looks like each string has 9~10 LEDs.
ok...so do you think the problem is in the panel? and the other circuits boards outside are ok?
how much are you sure? 90% 50% ?

looks like an epic work....
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Old 12-12-2014, 02:41 PM   #52
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Default Re: HP ZR2740w almost dead

You can verify that but removing the other VO wire and see the Voltage will also go up.
LED failure are very common in LCD TV and monitor.
No body can give you 100% answer, I do not have the unit right in front of me, I base my finding from the results you provided.
You can ask for second opinion.
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Old 12-12-2014, 05:33 PM   #53
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Default Re: HP ZR2740w almost dead

You can also do this:
http://www.badcaps.net/forum/showpos...&postcount=107
or this:
http://www.badcaps.net/forum/showpos...4&postcount=95
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Old 12-13-2014, 06:01 AM   #54
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Default Re: HP ZR2740w almost dead

At this point I also say it is the CCFL. In regular CFL light bulbs you can check the heating coil, but these CCFL's seem not to have that.
So you have 2 more test options: Make a CCFL tester out of an old monitor CCFL driver board and a small power supply or a battery and check each tube,
Or:
Swap the bad CCFL power wires around with a good one and see if the 60V move with the bad CCFL.

I am afraid... you are running out of testing options after that.
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Old 12-13-2014, 03:09 PM   #55
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Default Re: HP ZR2740w almost dead

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Originally Posted by CapLeaker View Post
At this point I also say it is the CCFL. In regular CFL light bulbs you can check the heating coil, but these CCFL's seem not to have that.
So you have 2 more test options: Make a CCFL tester out of an old monitor CCFL driver board and a small power supply or a battery and check each tube,
Or:
Swap the bad CCFL power wires around with a good one and see if the 60V move with the bad CCFL.

I am afraid... you are running out of testing options after that.
This LED backlit NOT CCFL, one of the LED string has open circuit that is why it shows 60V on VO4.

Last edited by budm; 12-13-2014 at 03:43 PM..
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Old 12-13-2014, 07:56 PM   #56
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Default Re: HP ZR2740w almost dead

Idea is the same, just make it fit for an LED. I guess I have my head wrapped around my own problem with an RCA TV that has a ccfl backlight or backlight driver board problem that shuts down after 3 seconds. Grr.
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Old 12-16-2014, 11:50 PM   #57
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Default Re: HP ZR2740w almost dead

Wow, very useful info here and so rare that my google searches led (no pun intended) me here and the thread is only a few days old.

I have a similar issue with my ZR2740W, but it no longer powers up or has the power light come on at all. Just flickered once last night and that was it.
I'll grab my Fluke from my work truck and follow along your trouble shooting with Wash. I am hoping mine is a power supply issue that I can fix easier than the the LED issue Wash seems to have.

Is it okay for me to post here to keep info consolidated on ZR2740Ws, or would starting my own thread as I go along be better?
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Old 12-17-2014, 07:51 AM   #58
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Default Re: HP ZR2740w almost dead

Please start a new thread with good clear pictures of both top and bottom sides of your board, it sounds like the standby power supply is not working.
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Old 12-31-2014, 09:42 AM   #59
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Default Re: HP ZR2740w almost dead

Quote:
Originally Posted by wash View Post
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?
I think the power board touched the LCD causing the shorts on power supply. To fix this, you can try insulating the power board from touching LCD by using thin plastic sheet between the power board and lcd.

There is not much clearance between power board and LCD. With little movement or shake, the power board will touch the LCD.
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Old 01-08-2015, 09:00 PM   #60
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Default Re: HP ZR2740w almost dead

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Originally Posted by Teeva View Post
I think the power board touched the LCD causing the shorts on power supply. To fix this, you can try insulating the power board from touching LCD by using thin plastic sheet between the power board and lcd.

There is not much clearance between power board and LCD. With little movement or shake, the power board will touch the LCD.
I just experienced this problem for the first time with my open box 2740w which I just bought. I'm still in the warranty period after only 1 week. My display has a 2013 mfg date i this is helpful.

Based on your post i shook the display side to side on the stand and sure enough it came right on. What is your level of confidence that this is the issue?
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