HP ZR2740W - Flickered once and then wouldn't turn on

[fl0w3n]

I've had my ZR2740W for nearly two years now and the other night I was browsing the web, opened a new tab, and then the screen flickered once, the Blue power LED came on, then off, then everything went black and it was completely unresponsive to anything.

I can't get any signs of life out of it now.

I see Wash's thread and there is some great info in there, so I'm hoping people can help walk me through some trouble shooting the same.

I tried to test voltages at P804 and P803 like suggested to Wash, but with the power cord plugged in and the power board switch to ON, I get nothing, so I don't know if I need more components hooked up or that's my issue to start.

Pictures 1-4 show what I'm currently dealing with.
Picture 5 shows how I am attempting to test P804 and P803

[budm]

Re: HP ZR2740W - Flickered once and then wouldn't turn on

Lets start with checking the main AC fuse F801 (Black rectangular black box), if it shows <1 Ohms (depend on your meter probe resistances), then check the DC Voltage right at the two legs of two main filter caps (two large caps laying on their sides).

wash's thread:
https://www.badcaps.net/forum/showthread.php?t=42498

BTW, Please give straight shot pictures of both sides instead of an angle view.

[fl0w3n]

Re: HP ZR2740W - Flickered once and then wouldn't turn on

Thank you, budm.

AC fuse F801 has .01-.02 Ohm's, if that.

+C802 to -C807 yields 173.5 VDC
C802 yields 85.8 VDC
C807 yields 87.5 VDC

It appears I'm not receiving the voltage I should be at these main filter caps.

Sorry, the pictures are like that so that the ceiling lights don't reflect and create a glare spot. I'll try and retake them.

[budm]

Re: HP ZR2740W - Flickered once and then wouldn't turn on

So you read wash's thread, do you get the PS_ON signal? Wash's PS_ON was only 1.8V (it was stuck at 1.8V and does not change with power switch activation) which is not high enough to turn on the power supply and we had to use the resistor to force on the PFC circuit. He has problems in two boards, main not sending correct signal and power supply for the LED backlights.
I am beginning to think that it is not good monitor.

[fl0w3n]

Re: HP ZR2740W - Flickered once and then wouldn't turn on

So you read wash's thread, do you get the PS_ON signal? Wash's PS_ON was only 1.8V (it was stuck at 1.8V and does not change with power switch activation) which is not high enough to turn on the power supply and we had to use the resistor to force on the PFC circuit. He has problems in two boards, main not sending correct signal and power supply for the LED backlights.
I am beginning to think that it is not good monitor.

I get 0.0000 VDC when going from GND to PS_ON

However, this is with just the board and power cable plugged in, no other items connected (as I have pictured). Do I need to have the entire monitor connected together for testing this?

Well, I'd agree that there are common issues... I've owned 4 or 5 of these, but I picked this one up from eBay for $250 over a year back, got it warrantied by HP, and it lasted till now providing me awesome 1440p image. I also bought a second one for work for $165 that has a few dead pixels, but nothing I notice for general computing at work.

[fl0w3n]

Re: HP ZR2740W - Flickered once and then wouldn't turn on

Is this of any concern?

[budm]

Re: HP ZR2740W - Flickered once and then wouldn't turn on

Is this of any concern?

Do you mean the exposed shield? the shield is connected to ground (chassis).

[budm]

Re: HP ZR2740W - Flickered once and then wouldn't turn on

I get 0.0000 VDC when going from GND to PS_ON

However, this is with just the board and power cable plugged in, no other items connected (as I have pictured). Do I need to have the entire monitor connected together for testing this?

Well, I'd agree that there are common issues... I've owned 4 or 5 of these, but I picked this one up from eBay for $250 over a year back, got it warrantied by HP, and it lasted till now providing me awesome 1440p image. I also bought a second one for work for $165 that has a few dead pixels, but nothing I notice for general computing at work.

Power supply board, main board, switch board that is.

[fl0w3n]

Re: HP ZR2740W - Flickered once and then wouldn't turn on

All measurements on P803 are 0.0000 VDC

By the way, I'm using 3. PS_ON with positive lead of MM and 4. GND with negative lead of MM, just for clarification.

[fl0w3n]

Re: HP ZR2740W - Flickered once and then wouldn't turn on

Power supply board, main board, switch board that is.

Here is how I have it all connected now. The only things that aren't connected are the USB panel and the grounding screw as seen in the picture. Do I need to ground this screw to something?

[fl0w3n]

Re: HP ZR2740W - Flickered once and then wouldn't turn on

Okay, so I've been playing around with measuring various aspects of the C807 and C802 caps laying on their side, and keep getting weird results. They've tested between 208uF and 210uF, which is below their 220uF rating. The other 220uF caps on the board read around 230uF.

When I let the caps fully discharge I get one with millions of Ohms of resistance, and one in a full open condition where my M.M. reports 0L

When I plug power into the board they only have 170VDC when I know budm said in Wash's thread that they should be doing 320-340VDC

Could these possibly my culprit?

[fl0w3n]

Re: HP ZR2740W - Flickered once and then wouldn't turn on

Well I brought my second zr2740w home from the office so that I could see if I can figure out the issue.

C802 and C807 read the same on the good board, but I do get 5V readings across the 5V pins on the P803 and P804.

With that being said, it seems that my issue is somewhere between the two large black caps and the P804/3

I haven't had much time to tinker the past week, but has everyone already given up on me I need help with troubleshooting to isolate the issue in hopes of being able to replace a part

[Teeva]

Re: HP ZR2740W - Flickered once and then wouldn't turn on

Try putting insulation between the power board and LCD using thin plastic. This will prevent the power board from touching lcd and shorts the circuit.

I found this out after I bought one zr2740w that wouldn't turn on.

[selldoor]

Re: HP ZR2740W - Flickered once and then wouldn't turn on

I haven't had much time to tinker the past week, but has everyone already given up on me I need help with troubleshooting to isolate the issue in hopes of being able to replace a part

Well that is a laugh - you havent had much time to fix your own machine yet seem to think others have time to help??? Believe it or not we all have lives.
You are lucky in that you have lots of tests in washs thread and have a spare working machine to tests alongside so shouldnt need hands held.

Budm seemed to be working towards finding out if the PFC kicks n when you press the on button, but whilst you seem to have got so far you dont actually
say you did that. So with it all connected and meter on vDC600 connected
+C802 to -C807 what reading do you get when a) plugged in and b)
ON button pressed - you MUST monitor the voltage continuously so may need a helper.

[budm]

Re: HP ZR2740W - Flickered once and then wouldn't turn on

So you do not not PS_ON signal? PS_ON must be present for the PFC Voltage booster to work, you can easily verify that on the working unit.

[fl0w3n]

Re: HP ZR2740W - Flickered once and then wouldn't turn on

Try putting insulation between the power board and LCD using thin plastic. This will prevent the power board from touching lcd and shorts the circuit.

I found this out after I bought one zr2740w that wouldn't turn on.

I currently am using a ~ 1.5'x2.5' mousepad to insulate between the power boards and metal casing of the LCD. However this is just a temporary setup while I diagnose, are you implying a permanent solution?

[fl0w3n]

Re: HP ZR2740W - Flickered once and then wouldn't turn on

Well that is a laugh - you havent had much time to fix your own machine yet seem to think others have time to help??? Believe it or not we all have lives.
You are lucky in that you have lots of tests in washs thread and have a spare working machine to tests alongside so shouldnt need hands held.

Budm seemed to be working towards finding out if the PFC kicks n when you press the on button, but whilst you seem to have got so far you dont actually
say you did that. So with it all connected and meter on vDC600 connected
+C802 to -C807 what reading do you get when a) plugged in and b)
ON button pressed - you MUST monitor the voltage continuously so may need a helper.

Below I describe my results when checking the voltages across C802 and C807, and although I don't mention it, I get no change when power button is pressed.

I also tested this on my working display, and got the same voltage of ~170 VDC and again no change when button was pressed. This is odd because Wash seemed to get double this.

Thank you, budm

AC fuse F801 has .01-.02 Ohm's, if that.

+C802 to -C807 yields 173.5 VDC
C802 yields 85.8 VDC
C807 yields 87.5 VDC

It appears I'm not receiving the voltage I should be at these main filter caps.

Sorry, the pictures are like that so that the ceiling lights don't reflect and create a glare spot. I'll try and retake them.

[fl0w3n]

Re: HP ZR2740W - Flickered once and then wouldn't turn on

So you do not not PS_ON signal? PS_ON must be present for the PFC Voltage booster to work, you can easily verify that on the working unit.

It does not appear that I have PS_ON signal, as there is 0.0 VDC reading across all pins of P804 and P803, while the working unit does appear to have the correct 5 VDC readings (but no 12v).

I did not follow along with your suggestion to Wash on shorting the PS_ON with a resistor as he actually had some power to this area, and I have none.

[fl0w3n]

Re: HP ZR2740W - Flickered once and then wouldn't turn on

So I am re-orientating myself with where I left off, and re-performing some tests.

I am giving the name "Monitor #1" to the problematic one, and "Monitor #2" to the previously working one from my office.



With Monitor #1 hooked back up, both the beige and green PCB connected, with the LCD also connected, power switch connected, and even DP cable sending an image:

Voltage over (With power button both idle and pressed):
C802-C807: 171 VDC
P803 PS_ON: 0.00 VDC
P803 +12V: 0.00 VDC
P803 +5V: 0.00 VDC

[fl0w3n]

Re: HP ZR2740W - Flickered once and then wouldn't turn on

Interesting.

I combined Monitor #2's beige and green PCB, with Monitor #1's LCD panel and power switch and began to get the same results until I smelt burning. Everything was hooked up the exact same to my knowledge, and grounded the exact same.

Here's a picture of what I believe to have burnt, based off location of smoke and appearance after investigating. Unfortunately it's the best picture I can furnish at this time.