HP ZR2740w almost dead

[Mysza78]

Re: HP ZR2740w almost dead

Hello gentlemen
Does anyone know what type of LED is installed on the backlight bar?

[TeroYyy]

Re: HP ZR2740w almost dead

Back at this again, I noticed that the PSU board makes a rattle when I shake it, and it seems to originate from C812, a blue ceramic cap I suppose. It's right next to back light connector, seems to be between the ground potentials of hi/lo voltages. Could this be the culprit? I guess none of these parts should rattle..

[TeroYyy]

Re: HP ZR2740w almost dead

I replaced only the caps on the main board, not on the PSU board, since I can get it to wake up using the pull up resistor method. I replaced all electrolytic caps on it.

[remel]

Re: HP ZR2740w almost dead

Now I have replaced all the main board electrolytic capacitors, made no difference. Hmmm... What to try next.

did you replace the 'big' capacity and the small capacity electrolytic caps?
I've repaired many PSU and the problems were not with the big caps. Do you have pics or schematics of PSU? if send me pics maybe I can help you

[Snout]

Re: HP ZR2740w almost dead

Follow-up on a different problem - now and then lately the screen had begun to 'freeze up' and then fade to black, like a still image that then dims away. Other threads had suggested overheat under BGA chips on the control board, and since I'm no wiz with BGA-resoldering, I put a large 12cm 12V computer fan over the whole control board. So far it seems to have helped, the thing hasn't blacked out for the month or so it's been constantly turned on lately. Hurrah!

[TeroYyy]

Re: HP ZR2740w almost dead

Now I have replaced all the main board electrolytic capacitors, made no difference. Hmmm... What to try next.

[TeroYyy]

Re: HP ZR2740w almost dead

I just measured this some more, seems the problem is in the main board as I was able to get the back light on using pull ups to PS-ON and On/Off. So it seems the main isn't giving enough voltage to wake up the power supply board. Are there any suggestions on what might be wrong with it? I'm thinking of caps because the problem began just like a dying power supply problem starts, randomly not starting up and eventually not at all.

[Snout]

Re: HP ZR2740w almost dead

One interesting thing I found was that when I plugged my monitor into a UPS outlet (APC SmartUPS 1400), it behaved very erratically. Even though the UPS is line-interactive, and connected to the same outlet as the non-UPS stuff.
When plugged in non-UPS, it works.. mostly fine. Just a few quirks.

So there's another curio for people to watch out for.

[TeroYyy]

Re: HP ZR2740w almost dead

Hello all!
I have this very same monitor on hand, started blacking out erratically at work, got replaced and brought it home. Soon didn't work at all. Blue light for a few seconds, then amber. Didn't get any voltage readings measuring the LED-connector. On the P803 the 5V is live, but 12V pins don't give anything. Thinking of PSU board having an issue with that. Do the LED drivers have their own transformer(s) or are they related to this 12V output? Any suggestions on this? All the caps look fine, but I haven't tested them in any way.

[budm]

Re: HP ZR2740w almost dead

Glad to hear it is fixed, it is nice monitor but with poor workmanship.

[Gargy]

Re: HP ZR2740w almost dead

Hi Budm,
awesome, really smart diagnostic, it really helps me.

My issue was aslo with backlight and high voltage on VO4, the real reason had been the "unsolgered" the connector on LED strip. That was all.

Once again - BIG thank you - Only one forums on internet that nicely and straigforward leads to solve my problem.

Petr
Czech Republic

[mikolajj]

Re: HP ZR2740w almost dead

Helo,
My case stops here.

Hello,
finally I had enough time to investigate everything again.

The problem was broken LED stripe connector, when it was pressed everything was fine. After a moment everything went wrong. That's why I get 30V per LED power line every time.

I have soldered new connector and everything is fine now. Everything works like a harm.

Good thing is that during replacement of caps I have wrote down their values. I this is what I have found:

 Motherboard
C66	100uF	16V		⌀ 8mm	h 8mm
C67	100uF	16V		⌀ 8mm	h 8mm
C42	100uF	16V		⌀ 8mm	h 8mm
C48	470uF	16V		⌀ 8mm	h 9mm
C45	220uF	25V		⌀ 10mm	h 13mm
C50	220uF	16V		⌀ 8mm	h 8mm
C15	4.7uF	50V		⌀ 5mm	h 12mm
C51	100uF	16V		⌀ 8mm	h 8mm
C52	100uF	16V		⌀ 8mm	h 8mm
C55	100uF	16V		⌀ 8mm	h 8mm
C57	100uF	16V		⌀ 8mm	h 8mm
C60	100uF	16V		⌀ 8mm	h 8mm
C59	100uF	16V		⌀ 8mm	h 8mm
C70	100uF	16V		⌀ 8mm	h 8mm
C71	100uF	16V		⌀ 8mm	h 8mm
C521 	100uF	16V		⌀ 8mm	h 8mm
C529 	220uF	25V		⌀ 8mm	h 8mm
C515 	10uF 	16V		⌀ 4mm	h 8mm
C514 	4.7uF	50V		⌀ 5mm	h 12mm
C530 	220uF	16V		⌀ 8mm	h 8mm
C528 	220uF	16V		⌀ 8mm	h 8mm
C527 	220uF	16V		⌀ 8mm	h 8mm

Power supply board
C840	100uF	100V		⌀ 10mm	h 17mm
C823	100uF	50V		⌀ 8mm	h 12mm
C826	680uF	25V		⌀ 10mm	h 17mm
C831	1000uF	16V		⌀ 13mm	h 17mm
C825	680uF	25V		⌀ 10mm	h 17mm
C832	1000uF	16V		⌀ 13mm	h 17mm
C833	1000uF	16V		⌀ 13mm	h 17mm
C835	1000uF	16V		⌀ 13mm	h 17mm
C834	1000uF	16V		⌀ 13mm	h 17mm
C836	1000uF	16V		⌀ 13mm	h 17mm
C828	400uF	25V		⌀ 10mm	h 17mm

[Snout]

Re: HP ZR2740w almost dead

Yep, when doing finicky work, like soldering, I have a steady-mounted 'helping hand' grip holding the details, and -being nearsighted- sit fairly closely leaned down without glasses to get a sharper image than a magnifying glass would get me. I'm good enough for thru-mount soldering, and relatively large things like big SMD details, but where it's small _and_ close by, about a micro-USB is the smallest I might (with luck) manage. Oh, the woes of being old.. that is, above fifteen or so.

I can add, as an aside, that if you have a _lot_ of old junk lying around.. in my case a later-than-2010 27-inch iMac (with dead graphics card), that the display in it was exactly the same! Except, of course, that the connectors were in the wrong places so it wouldn't fit in the HP's original case. But hooking up the HP's control circuits to the Mac's screen also produced a working monitor. Of course with the HP's limitations of no OSD or menus etc. ... Strange how things work out sometimes. (It just occurred to me to post this here, now that I got notified of a post in this thread.)

[mikolajj]

Re: HP ZR2740w almost dead

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.

Helo,
My case stops here.
Everything is disassembled on my desk.

When I turn on main switch S801 LED are On with hight backlight (bright), after few seconds thay dimm to 50% (let's name it like that, but it's not mesured 50%), and after another few seconds thay dimm even more - again let's say 25% of light.
After that, they stay lighten up all the time but very dimmed.
No input signal is given form PC, but there are pull-up resistors to force 3.PS-ON and 2.On/Off - so, turn on power supply and force LEDs to light up.

Force switching power supply and backlight LEDs
3. PS-ON pulled up to 5V (I've mesured 4.7V)
2. On/Off pulled up to 5V (I've mesured 4.7V)
1.V.adj pulled up to 5V (I've mesured 4.7V)

This gives exactly what I wrote at the begining.


Other tests
- fuse F801 has 0.4Ohm resistance
- before turning F801 on I get 5.2V on 5V rail on P803
- before turning F801 on I get 0.1-0.3V on 12V rail on P803
- before turning F801 on I get 1.9V on 3.PS-ON on P803
- before turning F801 on I get 1.9V on 2.On-Off on P803
- before turning F801 on I get 1.9V on 1.V.adj on P803
- after turning F801 on, I get 11.4V on 6 and 7 pins on P803
- testing voltage on P804 (switch on and off every time) gives ~30V on every pair - every time and it stays 30V even after voltage drops from 400 to 300V on big caps (C807 and C802)
- Mesuring 5V and 12V on P803 I have notice huge ripples - see attachement
This ripple is higher when I read 400V between caps and drops a little after voltage drop to 300V (on caps)

When I switch main power-switch S801 on, I get 400V between C807(-) and C802(+) for about 3.5s and after that it drops to ~300V (see attachement).

Reading other posts about this monitor model I think there's problem with PFC Voltage Booster, but I have no idea how to test it?
How to check if it's I801 or sth arround?
- diode D802 gives 0.48 forward Voltage and OL backwards in diode test mode - so it's fine
- transistor Q801 - soldered out gives:
- S > D 0.53V (red to S to black to D) in diode test mode,
- D > S OL (red to D to black to S) in diode test mode - correct
- diode D803 - forward voltage 0.58 (opposit way OL) - correct

Second issue are ripples on 5V and 12V rail on P803.
While I pulled up 3.PS-ON an 2.On/Off I can see huge ripples during 400V PFC booster work and little bit smaller ripples during 300V PFC Booster work. Should't the ripples be much smaller?
Can you look into attachment and compare it with your knowledge and experience?

What else can I test to find this broken piece of board?

There's one more thing I have noticed looking to other people photos.
Someone have replaced 7 capacitors (LED power): C864, C862, C854, C852, C848, C847 and extra C883 - which is much smaller on other photos.
Capacitors I have now are all 50V 220uF - so question is what values should be there, because I cant find angled photo ;-) and from the top they look like C835 for example?

[Snout]

Re: HP ZR2740w almost dead

I've used solder paste in the past and hot air too attach micro USB connectors.
It can be a little tricky getting the correct amount out though. I find using my iron easier.
I do work looking through a stereo microscope, so I find this sort of work easy. Try resting your hand on your workbench to improve the steadiness.

Yep, when doing finicky work, like soldering, I have a steady-mounted 'helping hand' grip holding the details, and -being nearsighted- sit fairly closely leaned down without glasses to get a sharper image than a magnifying glass would get me. I'm good enough for thru-mount soldering, and relatively large things like big SMD details, but where it's small _and_ close by, about a micro-USB is the smallest I might (with luck) manage. Oh, the woes of being old.. that is, above fifteen or so.

[diif]

Re: HP ZR2740w almost dead

One thought, that wasn't used this time though, is that when it comes to that tiny, finicky connector between strip and cable, perhaps squirting in a little conductive (silver) glue might do the trick?
That's definitely for the more steady of hand than I. I'd get that little blob all over the place..

I've used solder paste in the past and hot air too attach micro USB connectors.
It can be a little tricky getting the correct amount out though. I find using my iron easier.
I do work looking through a stereo microscope, so I find this sort of work easy. Try resting your hand on your workbench to improve the steadiness.

[Snout]

Re: HP ZR2740w almost dead

Do I get to pick the hat ?
I've repaired LEDs using hot air and the hotplate. The hot plate gives much cleaner results with much less chance of burning the board or LEDs.

One thought, that wasn't used this time though, is that when it comes to that tiny, finicky connector between strip and cable, perhaps squirting in a little conductive (silver) glue might do the trick?
That's definitely for the more steady of hand than I. I'd get that little blob all over the place..

[diif]

Re: HP ZR2740w almost dead

To: 'diif'

I get it in general, but I will "eat my hat" if I hear of anyone successfully repairing this strip using this method. I managed to do it OK with hot air in the end but wasted almost 50% of the new LED chips I had in the process.

Do I get to pick the hat ?
I've repaired LEDs using hot air and the hotplate. The hot plate gives much cleaner results with much less chance of burning the board or LEDs.

[Snout]

Re: HP ZR2740w almost dead

OK, there's good news and bad news for you:

Good news:
- that problem is almost definitely the connector. You caught it open circuit once, but now its working. This means you don't need to find the LEDs and you don't face the problem of soldering them
- you almost have a nice working monitor!

Bad news:
- even fixing the connector is tricky. You will be able to do it with an iron rather than hot air but it is an SMD part with a small pitch; you need to have a good fine iron and be good at soldering. I think i posted pics of it.
- it is easy to rip the connector off the board completely when disassembling, making it harder to fix
- it only works on 1440p & VGA. You need DVI dual link cables for 1440p and thus it won't work via an HDMI adaptor - you need DVI or DP on your graphics card.

Good luck!

Quite right - with a fresh bought DVI-D cable (at first I tried with what I had at home - a HDMI cable with a passive DVI-D adapter in each end ;P ) I now have a working monitor, with 2560x1440 on both DVI and DP inputs. Phew!

Well, it's been fun fixing up a large LED-strip monitor! My experiences so far have been with CCFLs only, tht electronics and tubes, and with 'single strip' smaller screens, such as laptops, where replacing the strip is as easy as cutting a length of a 5m spool of Generic Chinese White LED.

++knowledge; // for the win.

[cmg]

Re: HP ZR2740w almost dead

OK, there's good news and bad news for you:

Good news:
- that problem is almost definitely the connector. You caught it open circuit once, but now its working. This means you don't need to find the LEDs and you don't face the problem of soldering them
- you almost have a nice working monitor!

Bad news:
- even fixing the connector is tricky. You will be able to do it with an iron rather than hot air but it is an SMD part with a small pitch; you need to have a good fine iron and be good at soldering. I think i posted pics of it.
- it is easy to rip the connector off the board completely when disassembling, making it harder to fix
- it only works on 1440p & VGA. You need DVI dual link cables for 1440p and thus it won't work via an HDMI adaptor - you need DVI or DP on your graphics card.

Good luck!