HP ZR2740W troubleshooting

[stj]

Re: HP ZR2740W troubleshooting

soo.

some foto's
an lg 4pin driver usnig 1 common & 2 sequenced chanels.
the chip is missing on the board because it blew.

and a 6 chanel 10pin driver that a cut from a broken laptop display to use as an upgrad on anothe machine.
(yes - that trick works)

and some strip foto's

[momaka]

Re: HP ZR2740W troubleshooting

good luck with that theory,
i'll post some foto's of a strip, and driver board soon.

@ stj: laptops are a little "different" from large screen desktop LCD screens like this one.

If you look again at the bottom side pictures that Stifle9 provided, there are 6 "VO" lines on connector P804 and 6 ground connections. No signal wires present whatsoever. If there was such a driver that you speak of "elsewhere", then how would the monitor controll the LED backlight brightness? That simply just doesn't make sense to me. Moreover, look at the LED "inverter" section of the PSU again. As detailed in my previous post, the jumpers next to the caps in that section are to signal to the controllers if there is a fault with any of the LED VO lines (e.i. either overvoltage or overcurrent).

[stj]

Re: HP ZR2740W troubleshooting

well i looked at the foto's,
and it's very unusual - and a poor design.
all the ones i'v seen - and i'm not talking laptops.
use a single coil to step the voltage up and then use fets - usually in the controller, to drive the leds with pwm.
the controller ic has the current-sense, the fets and the sequencer etc all internal.

seeing that row of coils is just strange.

i'd id the controller chip & get a datasheet.
(and if you tell me there is no controller chip then id fit one or trash it)

[Davi.p]

Re: HP ZR2740W troubleshooting

If the op decides to write here the marking on those 3 ic we can search the datasheet that we hope contains an application circuit.

[stj]

Re: HP ZR2740W troubleshooting

being that it's HP brand, there is probably some schematics someplace.

[Stifle9]

Re: HP ZR2740W troubleshooting

give me an idea of which 3 "ic"'s you are talking about and I can search for identification markings on them.

[stj]

Re: HP ZR2740W troubleshooting

small square ones probably with no pins on them.

[stj]

Re: HP ZR2740W troubleshooting

btw, there must be diodes under the board between the transformers and capacitors - worth checking them.

[Davi.p]

Re: HP ZR2740W troubleshooting

Stifle9 that was already indicated to you by Momaka on post 17 but i add one, so them are I810 I815 I814 on the bottom side photo near the screw hole at hour 1:50

[bammbammfran]

Re: HP ZR2740W troubleshooting

Well
maybe I am looking at this board completely wrong ? and it is tough to follow traces from pictures, but, it sort of looks to me like there may be 3 circuits for 3 strings of bulbs (NOT 6) (probably 20 or 22 bulbs per strand) --I have worked on a few led apples and the 24" apple uses 3 x 20 for 60 leds total.
It looks like V01 is the neutral side and that probably V02 is the positive side of the first strand. which would make v03 (-) and v04 (+)strand 2 and v05 and v06 strand 3.
SO, if this is the case, you should be probably pushing out 60+ volts at 2,4 and 6 depending on the last dim setting
you can probably confirm this by unplugging the board and using another power source to drive positive power into V02 and checking to see if it comes out of V01 then do 4 and 3 and 6 and 5
If you have a blown open bulb in one of the circuit- power shouldn't travel through)

I have been known to be wrong on occasion and I will admit it
I have repaired over 3000 monitor power supplies, but I am self taught and have not done many led boards

Still learning !!

[Stifle9]

Re: HP ZR2740W troubleshooting

ok, here are the ID's for the IC's: (there are 3 lines on each, separated by |)

I810 & I814: Z103WA | (Texas instrument symbol?) 13M | ATZE G4
I815: UTC NLCA | LM358G | 01

[Stifle9]

Re: HP ZR2740W troubleshooting

I have access to a digital power supply that could produce up to 18V and 3A (prob not at the same time lol).

[Stifle9]

Re: HP ZR2740W troubleshooting

stj - I think that I did test those rectifier diodes that sit between the transformers and the capacitors in post #16?

[Stifle9]

Re: HP ZR2740W troubleshooting

I had already written down the series but I neglected to include it with list of info I supplied before.

All caps are Lelon brand:

2x 250V 220μF A114(M) RPL 105ºC
6x 50V 220μF A101(M) RZW 105ºC
3x 50V 100μF A040(M) RXW 105ºC
1x 25V 470μF A110(M) RXW 105ºC
6x 16V 1000μF A114(M) RZW 105ºC
2x 25V 680μF A114(M) RZW 105ºC

[Stifle9]

Re: HP ZR2740W troubleshooting

Here is a picture of the driver board and close ups of a few parts that look somewhat melted? Taking a cue from stj and post #18 I looked at the tops of some of the chips on the driver board and I cannot read much on the tops of these 2 chips U20 and U502 because they seem to be melted... I cleaned them off with some alcohol before it took the photo

[stj]

Re: HP ZR2740W troubleshooting

that melty look is flux or laq - you can scrape it off.

[bammbammfran]

Re: HP ZR2740W troubleshooting

The last pictures are of your main board.
All that does is send power to turn on the power on on the led power side of the board.
Your boards do not have an LED driver chip like the 24 pin surface mount one that is on the pictures of the laptop driver board that is shown in #21.

I believe that yours is more like a ccfl inverter
It looks like power from the main board goes to I810-I814 and I815 and those power up the T804 T805 and I assume T803 transformers (can't read that number) -- I can not tell if I810-I814 and I815 are in series or parallel or if they are all the same part number. I think that they are pretty standard transistors and that your issues are here or in the leds.

with the boards powered up and with it connected to a computer, check to see if you have voltage at Vadj, On/Off and PS-on
My guess is that: Vadj, On/Off will probably be around 3 volts ? Vadj may show voltage even with the boards powered off and may show a lot lower voltage if the brightness was previously set high or low.
PS-on may be 5 volts ?? (It may also work in reverse and be grounding out 5volatge to power up)

Did you check the bulbs for continuity using a power supply to confirm if it is indeed 3 strings.
if it is 3 strings, the 18volt supply wont work because you will lose too much current through 20 leds.
if it is 6 strings, it might let a trace of current through
If you want to try it- just use the + from that power supply to feed the V06 etc pins. (Do not ground the board)
hook your tester ground to the supplies (-) then use the testers (+) probe to see what pin the power comes back out of. Don't touch the probes with bare fingers or you will get false voltage readings.

I usually take the led strip out to check them with a small supply. The last time I tried a set while the bulbs were in the unit was to hook some 12v batteries in series to get my voltage up.

another way to maybe tell if it is 3 or 6 strings is to unplug the led strip and check the v0x pins while trying to power it on to see which pins are getting +

[Teeva]

Re: HP ZR2740W troubleshooting

Recently I got a unit that had similar issue. When I pressed the power button, the power LED went blue for a few seconds then amber. I got it fixed by putting thin plastic to isolate the power supply board from touching the LCD. There wasn't much clearance between the ps board and lcd.

[budm]

Re: HP ZR2740W troubleshooting

https://www.badcaps.net/forum/showth...475#post621475

[commodore73]

Re: HP ZR2740W troubleshooting

@Teeva, that is hilarious. I had the same issue and suspected video drivers, power supplies and cables, video card and cables, and monitor failure, all sorts of suspects. After reading your message, firmly I pushed the power cable away from the back of the monitor, then the monitor worked again.