HP ZR2740w almost dead

[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.

[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

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.

[TeroYyy]

Re: HP ZR2740w almost dead

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

[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!

[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

[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.

[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..

[Mysza78]

Re: HP ZR2740w almost dead

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