Dell 2709w No power

[shiftd]

Re: Dell 2709w No power

Another idea to try. This worked for my monitor.

Just today my monitor of many years decided that it does not want to turn on anymore. The blue led doesn't light up with touch or proximity of a touch, no matter how many times I tried. Feeling sad and unhappy, I tried another monitor and ... figured out that the monitor was the issue.
After reading 5 pages of this thread and frustrated over my helplessness (even after trying to manually reset the board using instruction on post #12), I got upset and furiously plug and unplug the power cord from the monitor. Surprisingly, and a pleasant surprise at that, the blue led glows. After that, the monitor just works without a hitch.
When I unplug the power cord, and plugging it back, it still exhibits the same initial issue. The workaround of furiously plugging and unplugging still works and powering off the monitor by its power button (instead of power cord) doesn't seem to cause any issue.
It looks like the problem only happens when power was cut off from the monitor. Not a problem for me since I only turn off the monitor using the button.

To recap, I did not find the root cause. I just found a work around on the issue I had. Nevertheless, I am pretty happy about it. I hope you guys find this idea helpful.

[fatsubsonic]

Re: Dell 2709w No power

I have just finished replacing the chips i mentioned in my previous post (page5) unfortunately i have the exact same problem, nothing has changed. However i did notice IC652 & IC602 covered in a cream coloured residue which was liquid at some point... Im not sure if anyone has the same or could these chips but cooked???

[BeefyDog]

Re: Dell 2709w No power

I had the same cream colored "goo" that looks like the chip epoxy leaked from the sides of IC601 and IC651 as well as Q601 (on the top of the leg). There is evidence of heat damage on the trace & I noticed 1 of the SM diodes that looked cooked (it was, actually). I'm ordering a replacement power board (way too many components could be fried) for $30.
All this happened immediately after a power surge (the power company pulled the meter out and replaced it while I was away) -

[budm]

Re: Dell 2709w No power

Can I see the pictures of your board? It sounds like Silicone compound.

[BeefyDog]

Re: Dell 2709w No power

Can I see the pictures of your board? It sounds like Silicone compound.

I just got the new power board from yoycart.com , swapped out the old board, put it back together, and no joy. Still button lights up blue - totally unresponsive. The new board does not have the goo near/around the chips on it, but the old board could still be good.
I have to take apart the monitor and continue figuring out what the deal is, when I do, I'll snap some pics of the old and new.

[ScoreAddict]

Re: Dell 2709w No power

I also have a 2709WB with the same issue as Neill and ytsoc! I tried to reflow the chip yesterday but the problem remains.

But Neill also offered an interesting alternative:

I could try adding a capacitor in parallel with R460, in fact there is space for one on the board(C337). But that is modifying not repairing, this monitor has worked fine for a few years, it should not need modifying.

Any idea if this could actually work? And what value the capacitator would require?

And, deary me, does this monitor get HOT! No wonder there are heat issues!

[lalexan]

Re: Dell 2709w No power

My Dell 2709w didn't start, no signs of life except the blue power light.
I opened it and measured a steady 24V supply, w/o much ripple. Disconnecting the back-light module didn't do much, so that was clearly not a dried out capacitor issue. (Back light is always the biggest consumer and the heaviest load on the 24V supply.)
Then I was very lucky to find this awesome forum, especially the 2 page chat between ytsoc and Neill, which has enough details to fully characterize this type of failures. Post #4 is simply amazing, thank you Neill! My monitor had 3.3V and 5V supplies up and running. The ring oscillator of FLI30366 (416 pins BGA) was running at the right frequency (post #7). The heat sink was warm indicating life.
I2C keyboard connector signals didn't have any activity, stuck at about 3.3V. All this led me to conclude that the malfunction was identical to the one that ytsoc successfully diagnosed and cured.
Some of the BGA balls got disordered! The only solution – re-flow.
If proper equipment is available re-flow process is relatively simple and straight forward. See it yourself in this YouTube video – slowly preheat the board from the bottom to 140C-150C and complete the profile to 210C-220C from the top.
https://www.youtube.com/watch?v=lhZhHFO9x0Q
But without this equipment this job is anything but trivial - people use heat guns and ovens.
Oven produces nice even heat- great for solder but very bad for plastic parts and electrolytic caps. There were too many of them on this board so backing it in an oven at 200C wasn't a good idea. Heat gun solves this problem by generating localized heat, but that isn't very good for BGA re-flow, because the chip is super hot while the board is still too cold. Here is one of the most successful posts of at-home-re-flow with a heat gun. The main conclusion is – patience and temperature monitoring:
http://forum.thinkpads.com/viewtopic...609846fcadad6c
Additional critical element in the process is flux, which is needed to improve solder-stickiness. ytsoc mentioned it in post #34 and it is shown in the above video. W/o this re-flow has much poorer chances and the fix won't last long. Kingbo RMA 218 seems to be a very good choice. Please don't use Rosin Paste Flux.
I ended up preheating the board to 140C with a simple crepe maker. Temperature monitoring was done with a Digital Laser Infrared Thermometer (and Fluke Type-K thermocouple for double-checking). The top side of the board was covered with foil leaving FLI30366 exposed. The rest of the temperature profile was performed with a heat gun at a rate of 15C per minute. The monitor is working great again.

[diif]

Re: Dell 2709w No power

Nice work lalexan.

[ScoreAddict]

Re: Dell 2709w No power

Thanks for info, lalexan! Highly appreciated!

My own problem (literally) got worse on christmas eve! More and more graphics errors appeared which I (wrongly) blamed on my graphics card. These only appeared when the monitor got hot and in the native resolution (1920x1200).

So, I performed another reflow on the 25th of December. Using more flux this time and the heat gun instead of the SMD soldering station.

Well, this time it worked perfectly! No more graphics errors PLUS the power button issue is also fixed!

For this kind of "operation" I use aluminium foil to cover most of the pcb. Except for the (square) area around the chip (3cm x 3cm). The hot air gun is not really a "proper" tool for any delicate work since it only has two "speeds" to offer!

Switching to the slower speed will (usually) provide you with temperatures at about 350-400 degrees Celsius - if you keep the gun at a distance of about 5-10cm. Do not go any closer!

Setting 2 will deliver temperatures at about 500 degrees celsius, so absolutely not recommended!

5 minutes of use are sufficient! Plus some 20-30 minutes for the pcb to FULLY cool down. Take your time in this regard!

Also, do not perform this operation in a normal or even low temperature room! The kitchen actually is the best place. Heat the place up to about 35-40 degrees Celsius (with the oven).

Another additional option is to place the pcb above an oven plate at about 15cm-20cm height to provide some hot air from below. Setting the plate to a medium setting will do just fine (but don't use a gas oven!). No need to go much higher.

This will improve flux (heat from both sides) and also reduce the risk of heat/cold reactions on the board and ic.

I have done this - successfully - with several Playstation 3 ("fat"/slim) - and Xbox 360-consoles who suffer from exactly the same issue (mostly the GPU).

The better (and more expensive) solution is to do a "professional" reflow or even a reballing. If you have the equipment yourself or know some company/person to do it for you.

Since the problem of these ics losing their connections to the pcb are mostly related to cheap designs (in regards to heat dissipation) and the use of lead free solder these solutions may not work permanently! Even the more expensive ones. Just keep this in mind!

[lalexan]

Re: Dell 2709w No power

Congratulations ScoreAddict!
Glad it worked for you this time. In my experience flux plays an important role in the process.
MFG

[HermannS]

2709w stuck blue LED, main board reflowed

Hi,

I have also just revived a 2709 with the "stuck blue power LED" phenomenon. I used my reflow oven to fix the main board. It is working flawlessly again.

Yo can read the story in my blog here: http://alpengeist-tvrepair.blogspot....power-led.html

Thanks to everyone in this thread! I would have never guessed the solution myself.

Hermann

[fluxflux]

Re: Dell 2709w No power

Hi All,

just wanted to say "Thank You" as you helped me to fix my Dell 2709w.

I've reflowed it (preheating with a cooking plate; hot air SMD gun; put some new compound on the chip) and now it works again.

Also I've added a slim fan (from an old Pentium 1 system) together with a voltage regulator to the 12 V output . The fan was sticked to the heatsink. The fan is really quiet and ensures a constant flow.

Kind regards

fluxflux

[jdryyz]

Re: Dell 2709w No power

Picked up one of these monitors for $0. It has the same symptoms. A little worse in my case as the power button is missing. That may not matter since most the monitor will just go into standby when no signal is received.

I found a toaster over dirt cheap in a thrift store. I do not have any temperature control device, however.

Should I dare attempt a reflow if this is all I am working with?

[lalexan]

Re: Dell 2709w No power

Picked up one of these monitors for $0. It has the same symptoms. A little worse in my case as the power button is missing. That may not matter since most the monitor will just go into standby when no signal is received.

I found a toaster over dirt cheap in a thrift store. I do not have any temperature control device, however.

Should I dare attempt a reflow if this is all I am working with?

I wouldn't. Without temp control you will not be able to get far. You'll either burn it or won't reach the meting point and that's useless.
I'd at least grab a heat gun and an infrared thermometer at Harbor Freight for 25$ or so.

[barbapappa]

Re: Dell 2709w No power

Hi gang! I'm new to this forum and quite the rookie when it comes to repairing electronics. I've fixed some screens known for using bad capacitors in the past and now I'm faced with a larger obstacle: this screen. I picked it up in broken condition for $5. I have no information about how the monitor broke or in what way it started failing. I bought it broken and I get no response from the screen what so ever. I fear the previous owner might've damaged the power button in anger as it came off easily and I saw a piece of plastic was missing. That's a later problem if anything I reckon.

After opening it up I've found by visual inspection that a capacitor and resistor seems to be broken, and possibly a diode.

I've attached two pictures that shows the ceramic capacitor C633 (with text: R 102K 1KV) with a crack in it and resistor R603 burnt. I read in this thread that sergiobajo also suffered from a completely destroyed R603 and user diif helped out giving the resistance: "R603 is Brown/Black/Orange/Gold 10k Ohms 5%". Except these two components I can't see anything that's obviously damaged except perhaps the diode D608.

My plan would be to simply replace the capacitor and resistor. When googling "R 102K 1KV" I find that it's a 1KV 1000 picofarad capacitor, is this right?

Currently I don't even own a multimeter but I'm going to buy one tomorrow. I'm wondering if there's anything I've missed? Any components in particular I should inspect? Am I wrong that the capacitor is broken simply because of a crack in it?

[budm]

Re: Dell 2709w No power

That is a snubber cap, you should replace it with 2KV one instead.
Remove the cap and then do the resistance test between the two empty pads where the cap was to see what kind of resistance reading you will get.

[barbapappa]

Re: Dell 2709w No power

That is a snubber cap, you should replace it with 2KV one instead.
Remove the cap and then do the resistance test between the two empty pads where the cap was to see what kind of resistance reading you will get.

Allright. Not sure if I'm using this multimeter right or if the circuit is doing what it should be doing, but I'm not getting a constant reading after removing the capacitor and measuring over its pads on the circuit board. It's starting at around 15-20 MOhms and keeps going down. I saw it go down to 50 KOhm then it started to go back up again. :/

EDIT: If I leave it be for a while and then measure again I get 172 kOhm.

[kbs]

Re: Dell 2709w No power

hey noob question here, how can the outer casing of the monitor be opened?

I've looked at some videos for 2407WFP, but I'm not sure if they are relevant to the 2709w.

[lalexan]

Re: Dell 2709w No power

hey noob question here, how can the outer casing of the monitor be opened?

I've looked at some videos for 2407WFP, but I'm not sure if they are relevant to the 2709w.

Hey kbs,
the outer casing for 2407 looks a bit different but the idea is very similar. Make sure not to put pressure on the screen as it is the most fragile part of the monitor. For this reason I like to pry it open from the side instead. (see the attachment)

[Thomas W.]

Re: Dell 2709w No power

Nice Thread... an it isn't dead, it's still alive.
Today I got three of these Monitors today for 0€, all marked defect.

Two of them starts normal, one shows the "blue power led stuck" error.

I think, I will start with this monitor and do the lalexan method:

I ended up preheating the board to 140C with a simple crepe maker. ......The rest of the temperature profile was performed with a heat gun at a rate of 15C per minute. The monitor is working great again.

And best wishes to all of you fine people

regards
Thomas