Dell 2709w No power

[Neill]

Re: Dell 2709w No power

Problem is that the monitor is completely unresponsive, i can't turn it off.
I have had experience with replacing similar memories but simptoms were a bit different

Can you get an oscilloscope onto the I2C lines for the keyboard? See last photo in post #4, it shows the SDA and SCL lines. Is there activity on these lines? Failing that a DC Voltage reading from a DMM.

[ytsoc]

Re: Dell 2709w No power

25lv020 is a flash chip but i think the fw is in the tsop memory near the bga device(29lv160) because it has bigger capacity. the 25lv is perhaps where the settings are sotred
I'll get a scope in there later today.

[ytsoc]

Re: Dell 2709w No power

Just probed SCL and SDA pins, there doesn't seem to be any activity but they are both high at 3.2v

[Neill]

Re: Dell 2709w No power

Interesting. So you have a similar problem to mine. No I2C activity suggests that the main CPU has not initialized.

I am very interested to know if your monitor will initialize by manually resetting it. See post #12. Can you earth the junction between R279 and R460? You can just use your multimeter on current with one probe on earth and briefly touch the junction with the other probe. Safest way is to use a resistor to earth just in case you accidentally earth the wrong side of R279 and short out the +24V.

Also I hope it is not inappropriate for me to say that I'm very impressed with your English. It might be better than mine and English is the only language I know!

[ytsoc]

Re: Dell 2709w No power

Back with some more news.
The grounding of that via didn't help(it went down to 0.4v when grounded via a 1k resistor) so i went and probed some voltages and i seem to be missing the 12v one.
It seems to be obtained with a buck converter(L4978). I measured the potential at it's eneable pin and it's basically ground and accordin to the datasheet that means it's in sleep mode.
Can you tell me if that 12v rail should be on at all times?
Also, out of the 2 heatsinked cips only the bga one gets warm, the other one is stone cold
Ps: thank you for the compliments regarding my english.

[Neill]

Re: Dell 2709w No power

The 12V and one of the 5V rails ONLY come on when the monitor is powered on. The fact that you have no I2C activity means that the monitor is not in the powered on state.

I was hoping that the grounding of that point passed R279 would wake up your monitor.

For me also it is only the BGA chip that gets warm. The other chip with a heat sink is only enabled when the monitor is powered on, the 27MHz crystal beside does not oscillate until the 24V and second 5V rails are enabled.

Is the 19.6608MHz crystal near the BGA chip oscillating? I'm guessing it probably is because as you say the heat sink is warm.

[ytsoc]

Re: Dell 2709w No power

it's true, the main processor crystal is oscilating. i'm begining to think it's the processor that's gone.
I was looking to buy a board, but i can't find one in europe.

[Neill]

Re: Dell 2709w No power

So your monitor has 3.2V present and you cannot get the CPU to initialize by taking the low side of R279 to ground. It is even worse than my one.

I think that both of our monitors are beyond repair. I don't like to give up but there is not much you can do with a 416 pin BGA chip.

[Topcat]

Re: Dell 2709w No power

There was a dell 2709w on fleabay with a broken screen for 55 bucks. it appears to be gone now....but keep your eyes peeled for another one like it....working boards for cheap.

[ytsoc]

Re: Dell 2709w No power

yes i saw that one, but i doubt the seller was willing to ship to europe.
One last thing(as a hail mary) i'll try is to reflow the bga chip.

[Neill]

Re: Dell 2709w No power

yes i saw that one, but i doubt the seller was willing to ship to europe.
One last thing(as a hail mary) i'll try is to reflow the bga chip.

I was looking into reflowing that chip also, you are brave!

You can buy the FLi30336 in single quantities from Aliexpress.

One more thing you could try:

1. Cut the orange wire that goes from the PSU to the main board. cut it in the middle and strip back some insulation.
2. Plug the monitor in to the wall outlet and wait a few seconds.
3. Now join the orange wire.

This is not the same as ground the low side of R279.

[ytsoc]

Re: Dell 2709w No power

Good news and bad news:
Good news is that the reflow did the trick and the monitor now sort of works.

Bad news: when connected to a pc on any imput, the picture doesn;t come on, it goes to stand-by, if i disconnect the cable(dvi vga or hdmi) it says x cable disconected and it goes to sleep.

I can get into the menus and the monitor seems to working except it doesn't display any picture from the inputs

There might be 2 things that cause this:
1 the fact that i replaced that 25lv020 meory and now i can't seem to find it anymore
2 the bga chip is toast and now is only half working

Neil, do you have any means to read that 25lv020 memory?

[Neill]

Re: Dell 2709w No power

Neil, do you have any means to read that 25lv020 memory?

Not really. Nothing on hand but I guess I could program a micro controller(AVR) to read it and and send the data to a PC over serial.

What would you use to read it?

For the re-flow did you remove the chip, clean up the pads and re-ball the chip or did you heat it up without removing it?

[ytsoc]

Re: Dell 2709w No power

there's no need for reballing(or should i say no real advantage) just apply some flux and heat it up till the solder balls melt(be aware that those el caps won't like the heat and some will explode depending on how you do the reflow) .
The problems isn't with those balls but with those within the chip, so a correct fix is to replace the chip.

I have a small programmer( called minipro) that i use to read/program chips. It's pretty cheap and surprisingly(at least for me, a novice) it supports a great number of devices ranging from al sorts of memory chips to mcu's

[Neill]

Re: Dell 2709w No power

I have a small programmer( called minipro) that i use to read/program chips. It's pretty cheap and surprisingly(at least for me, a novice) it supports a great number of devices ranging from al sorts of memory chips to mcu's

I had a look at that programmer. Looks to be very good value. There are some on eBay for about USD$50.

I'm thinking now that I might just get a re-furbished 2709W from this eBay seller:

http://cgi.ebay.com/ws/eBayISAPI.dll...m=321368104396

Also I might try re-flowing the BGA chip. Funny, I have been in electronics for 25 years and I've yet to buy a hot air soldering tool.

[ytsoc]

Re: Dell 2709w No power

i'm curious if a reflow might solve your monitor's problems, it's a bit weird.

[ytsoc]

Re: Dell 2709w No power

hello again, neil, do you still have that monitor?
Could you please try and read that 25lv020 memory? I really need to rule that memory out as a cause for the monitor not displaying the input image

[rocket]

Re: Dell 2709w No power

I've come into possession of one of these monitors with multiple issues (vertical strips on the left hand of the screen which go away once warmed up, and recently failure to initialise).

It was pretty obvious that the previous owner (or someone) had attempted a repair but only succeeded in damaging a corner of the screen (now there are a few bright pixels where the screen is damaged - someone had inserted a screwdriver at the screen itself to pry the case open AND broken some clips at the corner). Unbelievable.

Initially on plugging the power light would flash blue and go out. I have to wait about 10 seconds between power ups to repeat the symptoms otherwise there'd be nothing happening. I could get it to eventually start after a number of rapid on-off attempts. Once warmed up it still start up ok even after power is removed and reapplied. But fails again when the monitor cools down.

So it does sounds to be a bad solder joint, possibly within the main cpu. I'll have to get the thing open later to see if applying pressure to the cpu will allow it to come on. If so then time to buy a hot air rework station!

ytsoc - where do you apply flux?

Hopefully the strips are fixable with some foam pads. The pixels are probably toast - I might apply a dab of marker ink on them - at least a 'dead' pixel is better than a bright spot.

[Neill]

Re: Dell 2709w No power

hello again, neil, do you still have that monitor?
Could you please try and read that 25lv020 memory? I really need to rule that memory out as a cause for the monitor not displaying the input image

Sorry have not been on here for a while. I don't have any easy way to read the contents of the chip. Perhaps I could de-solder and post it to you?

I've come into possession of one of these monitors with multiple issues (vertical strips on the left hand of the screen which go away once warmed up, and recently failure to initialise).

Initially on plugging the power light would flash blue and go out. I have to wait about 10 seconds between power ups to repeat the symptoms otherwise there'd be nothing happening. I could get it to eventually start after a number of rapid on-off attempts. Once warmed up it still start up ok even after power is removed and reapplied. But fails again when the monitor cools down.

So it does sounds to be a bad solder joint, possibly within the main cpu. I'll have to get the thing open later to see if applying pressure to the cpu will allow it to come on. If so then time to buy a hot air rework station!

.

Interesting. I too can get my one to come on by flicking the switch at the wall on and off quickly a few times.

I'm quite sure it is a problem with the FLi30336, either the chip itself or the soldering on the BGA package.

[ytsoc]

Re: Dell 2709w No power

So it does sounds to be a bad solder joint, possibly within the main cpu. I'll have to get the thing open later to see if applying pressure to the cpu will allow it to come on. If so then time to buy a hot air rework station!

ytsoc - where do you apply flux?

I don't know if the problem is a solder joint between the chip and the board, it could be within the chip(there are also connections inside the chip that fail due to thermal stress)

The flux is applied on the sides of the chip, once it's heated the flux will go underneath the chip and help with the reflow.


Thanks for replying neill, so you've given up on yours? how much do you want for that memory?