Dell 2408WFPb / 2408WFP - No Power

[Biessea]

Re: Dell 2408WFPb / 2408WFP - No Power

Ah ehy, these are my boards photos.

[Biessea]

Re: Dell 2408WFPb / 2408WFP - No Power

Hi Biessea,

try to heat up the heatsink on the mainboard and see whether the monitor powers on. I think you have the same problem as other forum members here.

Never buy a Dell monitor again

hey, I cleaned up the power supply board (there was a lot of dust at the end, I have this monitor bought at its exit on market, 2008 september so it's 9 years old and It's normal to find some dust solidificated)...then I tried to give current and the power on button LIGHT ON!
I was happy to see that so I decided to reassembly all and now monitor works perfectly! I'm so happy, this was the first time that I tear down my Dell and I succeded in my mission!
I'm so happy now, vertical lines appears like it do lately but after about ten minutes they disappear and the monitor works perfectly!
WOW!

Thanks for the support, anyway.

[eaarnoudse]

Re: Dell 2408WFPb / 2408WFP - No Power

Ok, that is great. But for a double check, you should cool down your monitor completely and check if it turns on again.

[dbrubeck]

Re: Dell 2408WFPb / 2408WFP - No Power

I am also trying to repair a Dell 2408WFPb. I have the same problem as mentioned in one of the previous posts. A led light that blinks one time and the monitor won't turn on. The power supply is OK, because CN701 has about 24V on the output. The reason that the inverter board doesn't power on is simple. The first black wire on CN701 is the ON/OFF signal and it's 0V.

I started to suspect the mainboard and I found a way to power up this board. It seems like there are two main sections on it. Each section has a big chip, a crystal and a voltage regulator. First, I measured the section at the side where the power supply cable comes in. The crystal has a perfect sine wave and the voltage regulator shows a perfect 1.8V. But there is no voltage on the second crystal and voltage regulator.

I heated the heatsink and the onboard chip in the first section very carefully with a hot air rework station. Then I tried to power up the monitor and it was working great again. I waited some time until the heatsink was cooled down. The monitor did not start up. I heated the heatsink and chip again and the monitor was working fine.

I think there is a cold solder joint in one of the pins of this chip. Maybe a reflow precedure will solve the problem, although this method is not very reliable. I hope this post will help other people to troubleshoot this specific problem.

Greetz,
Erwin

Thanks Ewrin, this was my exact problem.

By heating the big chip on the logic board to around 125 F (by blowing heat onto the heatsink, and measuring with an IR thermometer), I was able to get the monitor to turn on normally. After the chip cooled down, it would not turn on. Same results on repeat.

I expect that by leaving the monitor in standby, there will be enough heat generated to keep this chip warm and therefore allow the monitor to function indefinitely.

If the monitor gets turned off and cools, I should be able to boot the monitor by using a hairdryer through the lower vents to heat up the insides to ~125 F.

I'm curious if people on the board think that the root cause is inside the chip or a bad solder joint to the logic board. If this happens again, I might try a full reflow with flux and a heat gun and see if it makes a permanent fix.

Thanks!

[budm]

Re: Dell 2408WFPb / 2408WFP - No Power

Since there are lytics caps close by you may want really localized the heat or trying to localize the heat to the caps only and see what happen.

[eaarnoudse]

Re: Dell 2408WFPb / 2408WFP - No Power

Hi dbrubeck,

Another forum member (YulCmr) did some really interesting research lately. He did an X-Ray photography to check whether or not bad solder joints were present on the board. And the conclusion was there were no bad joints and all balls were OK. I am still convinced that the chip is damaged internally. And that makes the monitor immediately beyond repair...:-(

[AlaskaCC]

Re: Dell 2408WFPb / 2408WFP - No Power

I recently purchased a 2408WFP and have only been able to get the power light to come on a few times but was never able to get an on-screen display. I am a neophyte at component repair but am fair with a soldering tool. I was not able to detect any obvious problems through visual inspection.

After reading through the thread, I have confirmed there is 23.56 VDC at CN701. I checked every wire at the connector. The 23.56VDC is on the green wire and the yellow wire. I am not sure what else to do at this point. I can purchase a replacement board for ~$40 but hate to do that. I would appreciate some suggested next steps. Thank you.

[eaarnoudse]

Re: Dell 2408WFPb / 2408WFP - No Power

Hi AlaskaCC, I am afraid you purchased a bad 2408WFP and maybe your seller was aware of these problems before selling this monitor to you. I repaired about 3 2408WFP monitors and in all cases I had to replace the mainboard. I think this will be the only option for you.

You can also try to heat up the heatsink and see if it comes live. Good luck and keep us posted.

[AlaskaCC]

Re: Dell 2408WFPb / 2408WFP - No Power

Thanks for the recommendation. I will find a source for the mainboard and let you know the outcome.

[eaarnoudse]

Re: Dell 2408WFPb / 2408WFP - No Power

I bought the last one on AliExpress 2 weeks ago. I hope you will find a source elsewhere. Good luck :-)

[AlaskaCC]

Re: Dell 2408WFPb / 2408WFP - No Power

I purchased a replacement mainboard from an eBay seller that did the trick. I just completed the install. The monitor is back in business! Any idea what components fail on the mainboard or what causes the breakdown?

AlaskaCC

[eaarnoudse]

Re: Dell 2408WFPb / 2408WFP - No Power

Hi AlaskaCC, great that you fixed your monitor with the replacement part. As mentioned above, the problems are caused by the big chip (with the big heatsink on it). I replaced this mainboard for my customer last week and that monitor is working fine too.

[pvb_astro]

Re: Dell 2408WFPb / 2408WFP - No Power

I have the same symptoms as Sparrow-- but even after reading all the material here, no luck understanding. Power supply board appears to be good. later posts mention the heat gun solution, might try that next.

I"m an electrical engineer, but not a great technician.. workmanship issues.

bicycle's schematic is helpful, but my board might be slightly different, u601 is a NCP1203 for instance. An odd note- -D608 is missing, but so is the same diode on Sparrow's pictures. The schematic doesn't show CN702 which goes to the lamp high voltage supplies. is there a on/off control wire going over there?

Power on LED flashes when AC applied. PSU output at CN701 is 23 volts, Vcc for U601/6 is 15v, U601/1 adj= 0.99v, u601/2 FB is 1.00v. All good. A bypass capacitor on one IC on the main CPU board is 2.5volts. The opto isolators IC652 and IC602 appear to be off, U652/4 is 15volts, U602/4 is 1.00 volts, suggesting power is not commanded off?

[eaarnoudse]

Re: Dell 2408WFPb / 2408WFP - No Power

Try the heat gun solution...:-)

[wakoautz]

Re: Dell 2408WFPb / 2408WFP - No Power

Newbie here. Found this forum after searching for a fix for my 2408. Same issue as most of you guys here, green led on and that's it. I might want to try the heat gun solution before anything else and let everyone know the results.

[sirzur]

Re: Dell 2408WFPb / 2408WFP - No Power

So I wanted to post my workaround (NOT fix) for the Dell screen not [powering on. But to recap

• The fix is to heat up the heatsink on the onboard BGA chip
• Seem to imply that the BGA solder is bad, but someone had reflowed the BGA chip and that did not fix the problem
• X-ray photography shows that the BGA solder balls to be intact
• Speculation that one of the internal pins broken and only bridged with heat
• I confirmed that a hot hair dryer on the heatsink for a few minutes will subsequently allow the monitor to light up

Hack uses two resistors powered by a USB 5V source to heat up the heatsink of the BGA chip. The basics of the USB heater design are:

• 2 X 3W, 6.8 ohm connected in series to USB source
• Heat resistant sleeve where it contacts the heatsink
• V = I X R, therefore that current in the circuit is about 0.37A, below the 0.5A specification of a USB port
• Heating power = V X I = 1.8 watts between the two resistors, so I chose 3W rated resistors for adequate safety margin

The implementation was as follows:
• Old USB cable, but doubled up the line to reduce line resistance (Data+ and Data- cable used for power and neutral respectively)
• Heat sleeves to resistors, between resistors and also from resistors
• When circuit is soldered, do a trial with a 5V source to confirm that resistors heat up
• Outer heatsink fins bent outwards to create space for resistors. Resistors in contact with heatsink and just held in place by friction.
• Ensure no bare wire contact with heat sink
• USB cable routed under boards
• Cut made in right protective stainless steel cover and also screen back cover to allow access for USB cable
• I would strongly recommend to connect power to the USB cable to confirm that the heatsink is being heated up before reassembling the monitor







I attach some photos to show final implementation. To use it, either connect the "new" USB to a 5V source (a phone charger works) for a few minutes. I find that 2-3 minutes is all that is required on mine. Alternatively, power up the monitor - despite the screen not lighting up, there is power to the USB ports which can be used to heat up the heatsink.

Then power down the monitor at the mains and reapply power to the monitor and it should fire up. The reapplication of power is a necessary step as just heating the heatsink with power turned on to the monitor will NOT light up the screen

[eaarnoudse]

Re: Dell 2408WFPb / 2408WFP - No Power

Wow, nice work man! :-)

[Joontree]

Re: Dell 2408WFPb / 2408WFP - No Power

Hey guys, I have a 2408wfp that has been having issues as well. Recently I powered it on to find all blacks are being rendered as greens, some blues as pinks, and an overall static/grainy appearance to the image. These symptoms are consistent regardless of cabling or image source. The menu system and all buttons still work, though a factory reset didn't help. At first I suspected a bad cap but a visual inspection of the boards didn't reveal any obviously blown or bulging caps or components. I was wondering if anyone has had any experience with similar symptoms or any ideas for what to look at when troubleshooting for this specific issue. I can post pictures if that would be helpful.

[eaarnoudse]

Re: Dell 2408WFPb / 2408WFP - No Power

I think there are 2 possible causes. Maybe your T-Con board, or your LCD panel is faulty. I would try to replace the T-Con board first, because these board aren't very expensive. When you LCD panel is faulty, that will mean the end of your monitor...

[budm]

Re: Dell 2408WFPb / 2408WFP - No Power

Hey guys, I have a 2408wfp that has been having issues as well. Recently I powered it on to find all blacks are being rendered as greens, some blues as pinks, and an overall static/grainy appearance to the image. These symptoms are consistent regardless of cabling or image source. The menu system and all buttons still work, though a factory reset didn't help. At first I suspected a bad cap but a visual inspection of the boards didn't reveal any obviously blown or bulging caps or components. I was wondering if anyone has had any experience with similar symptoms or any ideas for what to look at when troubleshooting for this specific issue. I can post pictures if that would be helpful.

Did you try re-seating the LVDS cable yet?