Re: HP ZR2740W - Flickered once and then wouldn't turn on
This is what I found, but last night when I tried to check out it jist showed a blank page. I'll try again or call...
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Re: HP ZR2740W - Flickered once and then wouldn't turn on
I found this, if it helps
[url]http://www.eserviceinfo.com/index.php?what=search2&searchstring=tatung+pwb-1421[/url]Re: HP ZR2740W - Flickered once and ...pwb-1421[/url]...
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Re: HP ZR2740W - Flickered once and then wouldn't turn on
Yes, I am running with the original logic board.
The only thing that has changed is the PSU, the metal chassis that supports the PSU and Logic board, and I may have switched the PSU>Logic Board power cable and the Logic Board>LCD cables. I also added a cut-up ziplock bag between the back of the LCD and the PSU/Logic assembly, but I don't think it was doing anything as it was free to slide around. I figured it couldn't hurt though.
The original PSU was able to get voltage to the large main...
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Re: HP ZR2740W - Flickered once and then wouldn't turn on
This was with nothing plugged in. I was using Diode test mode on my Multimeter.
Even in Diode test mode, do I need power to the monitor?
Also, when I say I am touching the base, I only determined that by following another tutorial on "determining base through resistance". If looking at the transistor from the top, with the single leg on the top side and dual legs on the bottom side, the base was the top leg.
So it sounds like this transistor is not...
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Re: HP ZR2740W - Flickered once and then wouldn't turn on
Just to double check, I tested the visibly fried transistor on Monitor #2 and it of course shows a short.
In testing the original Monitor 1 transistor from the same location:
M.M. Black lead to Base
2nd terminal: 0.000 VDC
3rd terminal: 0.000 VDC
M.M. red lead to Base
2nd terminal: 0.000 VDC
3rd terminal: 0.374 VDC
Using resistance:
M.M. Black lead to Base
2nd terminal: 6.22 M Ohm
3rd terminal: 6.27 M Ohm
M.M. Red lead to...
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Re: HP ZR2740W - Flickered once and then wouldn't turn on
That was my first thought. The transistor that fried is also coincidentally right next to the grounding screw.
However, I did have everything mounted to the chassis as it would be normally assembled so it should have been okay. But there's always the chance of something going wrong when it's being open bench tested like I was.
I will test the transistors on the other board that look good, then. Thanks for the idea....
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Re: HP ZR2740W - Flickered once and then wouldn't turn on
Haha I just meant I wanted to make sure that what I was describing, shorting the PS_ON with a resistor, is what you're considering jumping the power supply.
As I suspected without 5V it won't do anything.
Yes, what is odd is that the transistor blew on my GOOD board (Monitor #2) that came from a completely different zr2740w which was working when I took it apart. So, either I somehow messed up when assembling, or my issue with the ORIGINAL (Monitor #1) actually lies in the LCD, TCon,...Last edited by fl0w3n; 01-06-2015, 05:39 PM.
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Re: HP ZR2740W - Flickered once and then wouldn't turn on
That was extremely helpful. Thank you.
I do recall Budm outlining the power board with the different sections, but I didn't even recall it because I wasn't sure what exactly I was looking at.
Now I can better understand your suggestion to go back to trying to jump start the power supply... And I assume that would be connecting PS_ON with the 5V Standby via a 100-1k Ohm resistor?
I can do that, but on the broken board I do not have any voltage what so ever to the 5V Standby...
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Re: HP ZR2740W - Flickered once and then wouldn't turn on
I checked this same chip on Monitor #1 thinking maybe this was the original issue, but it was fine.
I wonder if I accidentally did something wrong, or if the LCD panel on Monitor #1 is the issue and this was just the weak point on Monitor #2s pcbs.
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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....
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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...
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Re: HP ZR2740W - Flickered once and then wouldn't turn on
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....
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Re: HP ZR2740W - Flickered once and then wouldn't turn on
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....
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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...
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