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!
Snout
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Last Activity: 01-20-2020, 01:33 AM
Joined: 07-13-2017
Location: Broby
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Re: HP ZR2740w screen goes black
On mine, R810 was fine (showed about 350-400k and it's supposed to be 500k (edit: measuring while they were still on the board, which will skew the readings, but they were not shorted nor open) ) - also caution, those four resistors next to each other are _not_ in series! The first pair has one common pole, then both go separate ways. And the other pair likewise has one common pole, but the other ends don't go the same way, so I wouldn't just solder together the endpoints with one or two resistors.
Since I definitely can't...Leave a comment:
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Re: HP Elitebook 8440p flashes led 9 times
Yeah, a 1-wire chip like in Dell, HP,. and Macbook chargers, I'm aware of that, but had a spare old laptop to 'sacrifice' just to try it. I wouldn't advise this for _any_ machine, just saying it worked for me with a generic charger aswell, and the Elitebooks in question in particular. ... So, yes, there should be a warning attached 'try this at your own risk, you're likely to kill something in the lappy'.
Me, I'm just glad to have those extra three machines running without buying yet another 'reports...Leave a comment:
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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.Leave a comment:
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Re: HP Elitebook 8440p flashes led 9 times
Holy sheet, that worked! I have a Dell charger (19,5V, 4,62A), with the same middle-pin arrangement, that works perfectly well with an old HP/Compaq TC4400 (the tablet-PC). I got the 9 orange blinks on THREE DIFFERENT LAPTOPS and finally tried your short-center-to-plus, and am currently starting up, charging battery, and running memtest on the first one. GREAT solution!
*thumbs-up*...
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Re: HP ZR2740w almost dead
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...Leave a comment:
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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.
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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.....Leave a comment:
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Re: HP ZR2740w almost dead
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.
...Leave a comment:
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Re: HP ZR2740w almost dead
There was some strange glitch in the Vo4 line of LEDs. When opening the monitor up and checking each LED one by one with a multimeter, they all worked, and were all connected in a string. Of course the error hides when it's about to be spotted.. *snerk*
This may be more of a software question, just in case someone with this monitor has had the problem - the darn thing now seems to work in Windows (Win7) at a nice 2540x1440 through DisplayPort, giving picture; when I switch to the other source, an Ubuntu via a DVI cable, I...Leave a comment:
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Re: HP ZR2740w almost dead
Ouch, what a horror! And since it's inside the monitor itself, I bet buying a replacement strip would be just about impossible. Well, nothing for it but open and have a look, and pray it's just a bad connector that needs fixing!
Thanks for your tips!...Leave a comment:
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Re: HP ZR2740w almost dead
A sort-of related question: If not having a current-limited lab supply, but checking with 'just any 30V source', what type of resistor should I put in series with the LED strip I'm checking, to keep the current down (but not so low as to not light up at all)? Do I need a big power resistor to eat up current, or will just any resistor with the right ohm value do?...Leave a comment:
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Re: HP ZR2740w almost dead
Nice guide! I might try putting together a 30V LED-strip externally first and connecting it instead of the one Vo4 goes to, just to see if it lights up as it should, before taking the whole thing apart.. I know from earlier monitors that, at least with the tiniest bit of unstable hands, it's pure hell to piece all the layers back together again. >.<...Leave a comment:
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Re: HP ZR2740w almost dead
Wow. I have the exact same measurements! And they're negative, too (ie, with the multimeter black connected to monitor GND, the voltages show as -30 and -60 and 'rising' up towards zero, not positive values as one would expect.)
In my case also it's Vo4 that bumps to -60 after the first 'flash', and all others are at -30, then dropping off as the light's off. (Capacitors discharging when 'idle', I suppose.)
Have to peek around this thread now for hints, such as forcing BL_ON. Did you solve your problem by the...Leave a comment:
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