HP ZR2740w almost dead

[wash]

Re: HP ZR2740w almost dead

You need to force on both the PS_ON and the bl_on, you should then see the backlights come on and stay on.

ok, it doesn't happen, no flash, nothing.

[budm]

Re: HP ZR2740w almost dead

You need to force on both the PS_ON and the bl_on, you should then see the backlights come on and stay on.

[wash]

Re: HP ZR2740w almost dead

OK, that is good, the PFC Voltage booster is good, so now we can test the backlights by using another resistor to simulate bl_on (on/off) by connecting the resistor between the ON/OFF pin and the +5V, remove the ON/OFF wire also.
So far it sound like the main board is not putting out enough ps_on Voltage.

i reinsert the PS ON wire?

after i connect the resistor between the on off and the 5v i have to measure the voltage on the big caps?

done.

what should happen? nothing strange happens.

[budm]

Re: HP ZR2740w almost dead

OK, that is good, the PFC Voltage booster is good, so now we can test the backlights by using another resistor to simulate bl_on (on/off) by connecting the resistor between the ON/OFF pin and the +5V, remove the ON/OFF wire also.
So far it sound like the main board is not putting out enough ps_on Voltage.

[wash]

Re: HP ZR2740w almost dead

Sorry, +5V

ok so i remove the cable on the pin3, then i put a 1k between the pin 3 and one of the pin 5v (pin 12-14) then i check the voltage on the 2 big caps.

correct?

done.
it stays at @400VDC

[budm]

Re: HP ZR2740w almost dead

Sorry, +5V

[wash]

Re: HP ZR2740w almost dead

P803: PS ON
https://www.badcaps.net/forum/attach...8&d=1418243826

yes the PS ON is on the pin 3, but the 5VSTBY pin....i can't find it

is the 5v-sense?

[budm]

Re: HP ZR2740w almost dead

where is it?

PS

UNBELIEVABLE! the monitor i'm using now, has died 3 seconds ago....

P803: PS ON
https://www.badcaps.net/forum/attach...8&d=1418243826

[wash]

Re: HP ZR2740w almost dead

5VSTBY pin,.

where is it?

PS

UNBELIEVABLE! the monitor i'm using now, has died 3 seconds ago....

[budm]

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.

[wash]

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?

remains at 1.8v

[budm]

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?

[wash]

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.

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.

[budm]

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.

[wash]

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.

around 320 -330v.

[budm]

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.

[wash]

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.

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)

I also need good straight shot pictures of the bottom side of this power supply board.

this picture is ok?

[budm]

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.

[wash]

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)

[CapLeaker]

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.