HP ZR2740w almost dead

[wash]

Re: HP ZR2740w almost dead

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)

[budm]

Re: HP ZR2740w almost dead

This is what I come up with based on the pictures you provided.

[budm]

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.

[wash]

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.

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...

.

[budm]

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.

[wash]

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......

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) .......

[budm]

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.

[wash]

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.

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.

[budm]

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.

[wash]

Re: HP ZR2740w almost dead

OK, I do not get it, how can it goes below 0V (GND)?
But the bottom line is that I expect to see Voltage jumps up since you did indicate that the backlights did flash on for seconds, so it does not make sense as to you did not see any voltage on any one of the six outputs at all.

i really don't know

how much should be the voltage?

is there something else to do?

[budm]

Re: HP ZR2740w almost dead

no, show UNDER 0...

the indicator goes below 0, for all of them

OK, I do not get it, how can it goes below 0V (GND)?
But the bottom line is that I expect to see Voltage jumps up since you did indicate that the backlights did flash on for seconds, so it does not make sense as to you did not see any voltage on any one of the six outputs at all.

[wash]

Re: HP ZR2740w almost dead

All six of them (VO1~V06, six outputs) and ground show 0V?

no, show UNDER 0...

the indicator goes below 0, for all of them

[budm]

Re: HP ZR2740w almost dead

All six of them (VO1~V06, six outputs) and ground show 0V?

[wash]

Re: HP ZR2740w almost dead

Well, you can try to fix it to get the backlights to come on first, the problem can be the LED or the LED drivers circuit.
This will be lots of work since we do not have the diagram for the power supply/LED driver board.
You can check the DC Voltage on the P804 between
VO1 & GND
VO2 & GND
.............
..............
VO6 & GND
You will have to turn the monitor on and off six times to see if all the output show the same reading.

when i tested it before, it was 0.2 volt

i was using another ground, now using the grounds near the vo1 etc, the indicator of the multimeter goes UNDER the 0, what does it means?

[budm]

Re: HP ZR2740w almost dead

Well, you can try to fix it to get the backlights to come on first, the problem can be the LED or the LED drivers circuit.
This will be lots of work since we do not have the diagram for the power supply/LED driver board.
You can check the DC Voltage on the P804 between
VO1 & GND
VO2 & GND
.............
..............
VO6 & GND
You will have to turn the monitor on and off six times to see if all the output show the same reading.

[wash]

Re: HP ZR2740w almost dead

Pin1 Vadj of 4V then that is OK, no need to force on that pin 1 then.
So then you do have two problems:
1) the main board is not sending enough PS_ON Voltage to turn on the PFC and other section of the power supply, we proved it by using force on with the resistor.
2) The backlights still do not come on with force on method, so it can be the LED driver circuits or the LED problem.

there is something we can do about it?

[budm]

Re: HP ZR2740w almost dead

Pin1 Vadj of 4V then that is OK, no need to force on that pin 1 then.
So then you do have two problems:
1) the main board is not sending enough PS_ON Voltage to turn on the PFC and other section of the power supply, we proved it by using force on with the resistor.
2) The backlights still do not come on with force on method, so it can be the LED driver circuits or the LED problem.

[wash]

Re: HP ZR2740w almost dead

i have to measure it with the 2 resistor on the pin 2 and 3?

[wash]

Re: HP ZR2740w almost dead

OK, that can be due to we need the signal on the V adj pin (backlights dimming control).
Can you check the Voltage on that VADJ pin? I do not know if that signal if analog or PWM.

the pin 1 have

4v on pin 1

[budm]

Re: HP ZR2740w almost dead

OK, that can be due to we need the signal on the V adj pin (backlights dimming control).
Can you check the Voltage on that VADJ pin? I do not know if that signal if analog or PWM.