Dell 2408WFPb / 2408WFP - No Power

[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

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.

[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

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

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

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

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 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...:-(

[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.

[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!

[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.

[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.

[Biessea]

Re: Dell 2408WFPb / 2408WFP - No Power

Ah ehy, these are my boards photos.

[eaarnoudse]

Re: Dell 2408WFPb / 2408WFP - No Power

Good day, I had same power issue with my Dell, I opened it and this is the results. After a nice clean now the led on the power button on the bezel is ON another time, when before didn't light on.

1) Anyway, in the small caps at the right of IC652 I have voltage, fluctuating, from about 0.300v. to -0.100v.

2) the SMPS chip has this part number 1203P60. There is voltage on Vcc pin and it's fluctuating from 12.5v to 14.5v about. When I click on power button the voltage here is stable 14.5v.

PS: Here in Italy we have 220-230V. AC from the power supply line.

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

[eaarnoudse]

Re: Dell 2408WFPb / 2408WFP - No Power

Hi YulCmr and Locki. I read your last posts now. It's good to know that the solder balls on the BGA chip are ok after the x-ray photography, so reflowing this chip will be wasting your time... I am pretty sure now that the chip itself is faulty internally. Maybe one of the pins is internally broken. When you heat up the heatsink (and so the chip), the monitor will power on. After cooling down, the problem will be back!!!

There are more Dell monitor types that use similar chips on their mainboards and I have seen the same problem on these boards. Dell doesn't supply parts and when you try to contact them, they will never respond on your messages or call you back. It's pretty frustrating. That's why I recommend my customers nowadays to avoid buying a Dell monitor....

[Biessea]

Re: Dell 2408WFPb / 2408WFP - No Power

1) What is the DC voltage across that small cap (right of IC652)? Is it stable or fluctuating?

2) IC601 is likely your SMPS chip.

a) What is the part number?
b) Find the datasheet.
c) Is there DC voltage on the Vcc pin?
d) Is it stable or fluctuating?

3) I assume you have mains x 1.414 DC voltage across the large filter cap? That is 120 V AC x 1.414 roughly 165 V DC?

Good day, I had same power issue with my Dell, I opened it and this is the results. After a nice clean now the led on the power button on the bezel is ON another time, when before didn't light on.

1) Anyway, in the small caps at the right of IC652 I have voltage, fluctuating, from about 0.300v. to -0.100v.

2) the SMPS chip has this part number 1203P60. There is voltage on Vcc pin and it's fluctuating from 12.5v to 14.5v about. When I click on power button the voltage here is stable 14.5v.

PS: Here in Italy we have 220-230V. AC from the power supply line.

[YulCmr]

Re: Dell 2408WFPb / 2408WFP - No Power

Hi !

Back from the X-ray photography. No big deal. Every solder ball seems nice and good. Soooo .... the problem is elsewhere. I get it back today, I'll have a look to the board under a microscope.

Is it really impossible to get a service manual for this screen ? I can't find one, even a non-free version.

[locki]

Re: Dell 2408WFPb / 2408WFP - No Power

Hi YulCmr,

manufacturers use these BGA chips in combination with lead free solder.

I am afraid your monitor is beyond repair...

I had same problem, during cold morning i must sometime few times turn of and on againt to correct initialize ... so probably i have same issue

[YulCmr]

Re: Dell 2408WFPb / 2408WFP - No Power

eaarnoudse,

I asked for an X-Ray photography of the BGA chip at my work. I will update this thread as soon as I can got it. I hope I'll be able to see some failed solder balls.

[locki]

Re: Dell 2408WFPb / 2408WFP - No Power

it looks like power supply running, i can hear some little noise from 1203P60
i can measure voltages on CN701 connector ...

grey 3,24V
purple 3,2V
blue 0
green 23,17V
yellow 23,17V
orange 0
red 23,17V
brown 0,712V
NC
black 3,24V


problem was in R613 . I damaged it when i solder it .. infinite R measured

i can turn it on, and i can see low backlight but not menu etc ... so i probably fixed my power supply to state like before my mistake and short circuit ...