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

[fl0w3n]

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.

[Teeva]

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

Did you see the power led lit up? If the power LED lit up and displayed amber color, then the monitor is probably working fine, but it needs to be plugged in to the computer.

One thing I noticed when I tried to troubleshoot power issue on my ZR2740W for not turning on was this:The monitor wouldn't turn on without plugging video cable to the PC, and the power LED was amber.

[selldoor]

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

Hi If you still have a set of boards that are supposed to work I think you should go back to trying to jump start the power supply to see if the PFC is working.
You may have been misled or misled yourself here;
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.

No one commented on that but looking back it did need a comment. What you may have missed is that Wash is in Europe so on plug in he had 240VAC which on the big caps would be around 340vDC

As your AC is 120 on plug in vDC IS around 170v


EDIT when/if the PFC kicks in, then the voltage on the caps is lifted to 360vdc-400vdc
whether you are in the US or Europe.

[fl0w3n]

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

Did you see the power led lit up? If the power LED lit up and displayed amber color, then the monitor is probably working fine, but it needs to be plugged in to the computer.

One thing I noticed when I tried to troubleshoot power issue on my ZR2740W for not turning on was this:The monitor wouldn't turn on without plugging video cable to the PC, and the power LED was amber.

There are no lights what so ever from the LED next to the button, Amber or Blue.

[fl0w3n]

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

Hi If you still have a set of boards that are supposed to work I think you should go back to trying to jump start the power supply to see if the PFC is working.
You may have been misled or misled yourself here;
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.

No one commented on that but looking back it did need a comment. What you may have missed is that Wash is in Europe so on plug in he had 240VAC which on the big caps would be around 340vDC

As your AC is 120 on plug in vDC IS around 170v


EDIT when/if the PFC kicks in, then the voltage on the caps is lifted to 360vdc-400vdc
whether you are in the US or Europe.

Great info, that makes much more sense.

Can you help, what is the purpose/name of the green board and the beige board? Which is the PFC?

[selldoor]

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

Can you help, what is the purpose/name of the green board and the beige board? Which is the PFC?

The "beige" board in your set is the "power supply" or "power" board In your case the back of it is green. It is a PWB-1421. The black line across the board nominally separates high voltage "Hot" and low voltage "Cold"
Its purpose it to convert a single mains AC voltage into the various low DC voltages 3v 5v 12v and so on required for the main board to function.
In your case it also provides the voltage to drive the led back lights.


The green board is usually called the " main board" but has other names.
e.g "input board" as it has the input sockets. It carries the main processors and its basic purpose is to control and monitor the power supply and to process the signals from the input sockets and on off switch

You also have another small green board shown in washs thread
https://www.badcaps.net/forum/showthread.php?t=42498 that control the picture signals passed from the "main" board to the panel this can be called a Tcon or sometimes a panel board.

As regards PFC it is a circuit included ( in this case) on the power supply board. Budm shows the relevant section in this diagram on washs thread
https://www.badcaps.net/forum/attach...9&d=1418251967 - Most of the components are of course on the top of the board.
Hope that helps a bit

[fl0w3n]

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

The "beige" board in your set is the "power supply" or "power" board In your case the back of it is green. It is a PWB-1421. The black line across the board nominally separates high voltage "Hot" and low voltage "Cold"
Its purpose it to convert a single mains AC voltage into the various low DC voltages 3v 5v 12v and so on required for the main board to function.
In your case it also provides the voltage to drive the led back lights.


The green board is usually called the " main board" but has other names.
e.g "input board" as it has the input sockets. It carries the main processors and its basic purpose is to control and monitor the power supply and to process the signals from the input sockets and on off switch

You also have another small green board shown in washs thread
https://www.badcaps.net/forum/showthread.php?t=42498 that control the picture signals passed from the "main" board to the panel this can be called a Tcon or sometimes a panel board.

As regards PFC it is a circuit included ( in this case) on the power supply board. Budm shows the relevant section in this diagram on washs thread
https://www.badcaps.net/forum/attach...9&d=1418251967 - Most of the components are of course on the top of the board.
Hope that helps a bit

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 so I don't think that will be jump starting it.

Can you confirm I am understanding correctly?

[selldoor]

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

Well I cant really say if you understand I would read back through both threads and
on washs thread make notes on how to do the jump - you need to disconnect the wire
to the pson from the main (either de solder it or cut it in a place where you can re -join it
without too much difficulty.) As you say it isnt going to work if you have no 5vstby.
One problem to think about is we have no idea what blew the small transistor on the board
- presumably it could happen again ( any part no marking left on the small transistor?)

[fl0w3n]

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

Well I cant really say if you understand I would read back through both threads and
on washs thread make notes on how to do the jump - you need to disconnect the wire
to the pson from the main (either de solder it or cut it in a place where you can re -join it
without too much difficulty.) As you say it isnt going to work if you have no 5vstby.
One problem to think about is we have no idea what blew the small transistor on the board
- presumably it could happen again ( any part no marking left on the small transistor?)

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, or power switch.

After frying the transistor on the #2 board, I checked the original #1 board thinking maybe I had overlooked this same transistor frying and being the original issue to start with. However, it is fine on board #1 - which is good because I can now read the number printed on it and get a replacement.

[Agent24]

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

Transistors can be dead and not look fried.

Possibly you had the board shorting against some metal when you powered it up?

[fl0w3n]

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

Transistors can be dead and not look fried.

Possibly you had the board shorting against some metal when you powered it up?

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.

[fl0w3n]

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 Base
2nd terminal: begins at 80 K Ohm and quickly climbs
3rd terminal: begins at 1.1 M Ohm and quickly climbs


It appears the imprint on top of this transistor reads "D1 T0G".

[selldoor]

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

D1 is probably a BCW31
http://www.datasheetarchive.com/BCW31-D1-datasheet.html

[fl0w3n]

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

D1 is probably a BCW31
http://www.datasheetarchive.com/BCW31-D1-datasheet.html

Thanks!

Do my results make sense and indicate a functioning transistor?

[budm]

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

Your readings do not make sense to me.
These are in Diode mode testing or DC Voltage testing with the monitor plugged into the outlet?
In testing the original Monitor 1 transistor from the same location:
M.M. Black lead to Base
2nd terminal: 0.000 VDC =This should mean shorted (same reading as shorting two probes together) if you are in diode mode testing
3rd terminal: 0.000 VDC =This should mean shorted (same reading as shorting two probes together) if you are in diode mode testing

M.M. red lead to Base
2nd terminal: 0.000 VDC =This should mean shorted (same reading as shorting two probes together) if you are in diode mode testing
3rd terminal: 0.374 VDC

Using resistance:
M.M. Black lead to Base
2nd terminal: 6.22 M Ohm: But then it show resistance in Mega Ohm here
3rd terminal: 6.27 M Ohm: But then it show resistance in Mega Ohm here

M.M. Red lead to Base
2nd terminal: begins at 80 K Ohm and quickly climbs
3rd terminal: begins at 1.1 M Ohm and quickly climbs

[Teeva]

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

If you can locate the 5v source, then, I am sure, you can fix the power board.
If you get the 5v on P803, then power LED will be on but amber. In order to turn LED backlight on, you'll need to connect video cable to PC;otherwise, it won't turn on.

[fl0w3n]

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

Your readings do not make sense to me.
These are in Diode mode testing or DC Voltage testing with the monitor plugged into the outlet?
In testing the original Monitor 1 transistor from the same location:
M.M. Black lead to Base
2nd terminal: 0.000 VDC =This should mean shorted (same reading as shorting two probes together) if you are in diode mode testing
3rd terminal: 0.000 VDC =This should mean shorted (same reading as shorting two probes together) if you are in diode mode testing

M.M. red lead to Base
2nd terminal: 0.000 VDC =This should mean shorted (same reading as shorting two probes together) if you are in diode mode testing
3rd terminal: 0.374 VDC

Using resistance:
M.M. Black lead to Base
2nd terminal: 6.22 M Ohm: But then it show resistance in Mega Ohm here
3rd terminal: 6.27 M Ohm: But then it show resistance in Mega Ohm here

M.M. Red lead to Base
2nd terminal: begins at 80 K Ohm and quickly climbs
3rd terminal: begins at 1.1 M Ohm and quickly climbs

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 functioning on both boards, one fried and the other silently died? I will order some replacements, but likely will need to fix what ever blew them to start.

[fl0w3n]

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

If you can locate the 5v source, then, I am sure, you can fix the power board.
If you get the 5v on P803, then power LED will be on but amber. In order to turn LED backlight on, you'll need to connect video cable to PC;otherwise, it won't turn on.

I am not in front of the board right now, but would I be able to visually trace the 5V line from P803 backwards, testing components on the way, to hopefully find what ever is blocking 5V from being supplied to P803?

[Teeva]

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

I am not in front of the board right now, but would I be able to visually trace the 5V line from P803 backwards, testing components on the way, to hopefully find what ever is blocking 5V from being supplied to P803?

The area that I would get vdc, I remember, was in the area I hightlighted in the pic attached, so I would focus on that area. Please BE CAREFUL when work on the board, especially on high voltage area.

[fl0w3n]

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

Well, I've got my main up and running again... but it took a donor PWB-1421 from my second zr2740w.

So, obviously then the issue with my original monitor is the power supply.