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Old 04-13-2011, 09:56 AM   #1
gajones
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Default Dell 3008wfp faulty power supply

My Dell 3008wfp screen shut off completely one day. I took it to an engineer who replaced some parts on the power supply, and it worked for a short time before it died again. He replaced some more parts, but the same thing happened again, twice. Unfortunately for me I had bought a refurb model which only had a 1 year warranty.

The engineer tells me
Quote:
your power supply has a fault on the secondary side of the power supply. Diode D22 which is type V30120S (the rectifier diode for the 14 volt rail), is blowing after the monitor has been running for a day or so.
I've had no luck finding a replacement power supply (I found a site called lcdrepair.us but they no longer have any), or asuitable repair kit (the ones I've found contain capacitors but not the diode). I'm hoping somebody may know where to pick one up, or can offer some insight on how to fix it.

Last edited by gajones; 04-13-2011 at 09:59 AM..
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Old 04-13-2011, 10:05 AM   #2
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Default Re: Dell 3008wfp faulty power supply

would be odd for it to blow for no reason.
pics would help..

datasheet
http://bambooz.pytalhost.net/badcaps..._datasheet.pdf
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Old 04-13-2011, 11:36 AM   #3
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Default Re: Dell 3008wfp faulty power supply

findchips.com

http://www.findchips.com/avail?part=V30120S
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Old 04-13-2011, 12:21 PM   #4
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Default Re: Dell 3008wfp faulty power supply

hi my name is zen.just joined site.

i am the engineer currently working on this psu.

as gajones has posted my findings,i will add a bit more info.

i have about 20 years experience working in the electronics repair industry.mainly tv and audio.

i'm normally quite good with power supplies,but this one is difficult to work on as the diode mentioned only seems to blow after unit has been re-assembled and then after working for a few days.

i even managed to source the exact same diode from china as opposed to an equivalent i had replaced with originally.

i have replaced a few other components on the 14 volt rail which diode D22 is the rectifier of.

have also checked the electrolytic caps on that rail.they all have good esr readings and are high quality 125 degree ones aswell.

as i'm not that familiar with dell psu's,i guess i need advice from someone use to working on them.

will try and post some photo's when i have a chance to strip monitor down again.

a schematic of the psu may also be useful.

thanks
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Old 04-13-2011, 12:42 PM   #5
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Default Re: Dell 3008wfp faulty power supply

I think the 120v reverse voltage rating of the diode is a bit tight. If he lives in an area with high mains and the transformer has high leakage inductance then the voltage at the diode could spike higher than that. I would advise a 200 volt replacement.
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Old 04-13-2011, 12:45 PM   #6
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Default Re: Dell 3008wfp faulty power supply

i would try first by checking the resistors linked to the shottky diode,it seems to me that one is gone higher value,thus pushing more current to the shottky ,you will need the schematic,for resistor type and value,also check for any reverse voltage,this will cause the shottky to blow,as it seems this monitor stays ok for a day or so,then pops,suggesting a small voltage that is creeping up and biting the diode on the ass,also if all checks out ok,then consider a higher amp diode that maybe will take more current,as sounds as if it could be a design issue with that power board with current boardering on the amperage of the diode,you can go higher on the amps for the diode,just the same as you can step up the voltage for a cap(higher not lower dont forget!),also double check on the main fuse it should read 1 on a dmm,if higher this will sugest a short somewhere.
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Old 04-13-2011, 03:34 PM   #7
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Default Re: Dell 3008wfp faulty power supply

^^ Off topic. Totally.

The diode is 30A. The monitor draws 4A at 14v, if not lower. The high current rating is so that voltage drop can be kept low and they get away with a smaller heatsink. There are no resistors linked to the diode because it wouldn't make any sense, and the power supply only pushes as much current thru the diode as the controller tells it to. And if the controller tells it so it means the monitor needs that current.

Your only pertinent observation is related to the diode reverse voltage. And that indeed could be the cause.
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Old 04-13-2011, 03:50 PM   #8
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Default Re: Dell 3008wfp faulty power supply

An observation and a question.
The monitor apparently ran a year without problems, and now after running and getting totally warm the diode fails. Is there a possibility it could be as simple as re-soldering a transformer?
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Old 04-18-2011, 10:27 AM   #9
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Default Re: Dell 3008wfp faulty power supply

thanks for the input guys

will have another go at it.
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Old 07-03-2011, 03:42 AM   #10
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Default Re: Dell 3008wfp faulty power supply

unfortunately it hasn't been possible to fix - it runs fine uncovered, but replace the casing and it heats up and blows again.

I've come to the conclusion that the only way to fix it will be to replace the whole power supply, but I just can't find anywhere that sells them. Any ideas where I could try?
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Old 07-04-2011, 02:33 AM   #11
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Default Re: Dell 3008wfp faulty power supply

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Originally Posted by gajones View Post
unfortunately it hasn't been possible to fix - it runs fine uncovered, but replace the casing and it heats up and blows again.

I've come to the conclusion that the only way to fix it will be to replace the whole power supply, but I just can't find anywhere that sells them. Any ideas where I could try?

Hi bro...i have the same problem with you ....btw i just done searching for the part...by the way, u could buy the part for psu 3008 wfp the link below

http://item.taobao.com/item.htm?id=6930940343

its from china i think..by the way becareful shopping..try find trusted middle men to handle the shopping for you since its chinese website

hope u can fix ur 3008 wfp...i waiting for mine technician to fix mine.
i did follow ur thread @ dell support page seems they are helpless! ..there is still hope update ur thread when ur 3008 already fixed...
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Old 07-04-2011, 02:25 PM   #12
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Default Re: Dell 3008wfp faulty power supply

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Originally Posted by ezdy View Post
Hi bro...i have the same problem with you ....btw i just done searching for the part...by the way, u could buy the part for psu 3008 wfp the link below

http://item.taobao.com/item.htm?id=6930940343

its from china i think..by the way becareful shopping..try find trusted middle men to handle the shopping for you since its chinese website

hope u can fix ur 3008 wfp...i waiting for mine technician to fix mine.
i did follow ur thread @ dell support page seems they are helpless! ..there is still hope update ur thread when ur 3008 already fixed...
hi, thanks very much for the info - well done for finding the part, i've spent hours searching for it! Have you actually bought it from that website?
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Old 07-31-2011, 05:01 PM   #13
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Default Re: Dell 3008wfp faulty power supply

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Originally Posted by Th3_uN1Qu3 View Post
I think the 120v reverse voltage rating of the diode is a bit tight. If he lives in an area with high mains and the transformer has high leakage inductance then the voltage at the diode could spike higher than that. I would advise a 200 volt replacement.
I like your suggestion. I'm going to take a chance and not replace the Schottky Rectifier with the Vishay V30120S 120v reverse voltage. I'm going to try the STMicroelectronics Schottky Rectifier rated at 170v reverse voltage instead. http://search.digikey.com/scripts/Dk...5-ND&x=23&y=16

Hopefully this one won't burn out after a couple of days. I'll let you know how it goes. Thanks for the suggestion.
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Old 08-16-2011, 08:15 PM   #14
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Default Re: Dell 3008wfp faulty power supply

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Originally Posted by Lumberjack777 View Post
I like your suggestion. I'm going to take a chance and not replace the Schottky Rectifier with the Vishay V30120S 120v reverse voltage. I'm going to try the STMicroelectronics Schottky Rectifier rated at 170v reverse voltage instead. http://search.digikey.com/scripts/Dk...5-ND&x=23&y=16

Hopefully this one won't burn out after a couple of days. I'll let you know how it goes. Thanks for the suggestion.
Worked! And still running strong. The 170v STMicroelectronics part did the job.
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Old 08-17-2011, 05:22 AM   #15
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Default Re: Dell 3008wfp faulty power supply

Thanks for the report! We're always happy to hear success stories.
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Old 01-12-2012, 04:15 PM   #16
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Default Re: Dell 3008wfp faulty power supply

My monitor as well just died the power supply is the issue, the problem is dell will not give them what they need to try and fix it. Any chance you would be ok if i share this information with them to try, and fix my issue. After this experience i am not sure i will buy from dell anymore.

Last edited by mardon1975; 01-12-2012 at 04:23 PM..
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Old 01-12-2012, 04:23 PM   #17
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Default Re: Dell 3008wfp faulty power supply

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Originally Posted by mardon1975 View Post
Any chance you would ok if i share this information with them to try, and fix my issue.
Anyone who finds this via search engine is welcome to the info. It is good etiquette to credit the person with the solution.
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Old 03-14-2012, 07:51 PM   #18
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Default Re: Dell 3008wfp faulty power supply

Hi Guys. I'm new to this board having just found it, after having just had my Dell 3008 monitor fail 3 months outside it's 3 year warranty

I'm pretty certain my PSU has the same problem described here, and I've already bought some much higher rated diodes (STPS40170CT) to fix it. No-one's posted an image showing the D22 diode location (it isn't marked on my board), so I'm posting an attached image of where MY faulty diode is located and wonder if someone could confirm that this is the infamous D22 on the 14V rail?

I also thought it would help others to know where to look after they'd managed to open up the Dell monitor (now that was one hell of a difficult job. How on earth do Dell repair them - maybe they just scrap and replace in-warranty items?).

If anyone can confirm I'm looking at the right device then it would help enormously before I start dismantling the heatsinks to get at the failed device (which isn't all that easy even for an experienced elec. eng.). I have visually confirmed that the faulty device marked in my photo is a 30120S.

Thx.
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File Type: jpg DEll3008PSU_Faulty_Diode.jpg (228.4 KB, 431 views)

Last edited by Jetset; 03-14-2012 at 08:37 PM.. Reason: Added info.
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Old 03-14-2012, 10:19 PM   #19
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Default Re: Dell 3008wfp faulty power supply

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Originally Posted by Jetset View Post
No-one's posted an image showing the D22 diode location (it isn't marked on my board), so I'm posting an attached image of where MY faulty diode is located and wonder if someone could confirm that this is the infamous D22 on the 14V rail?
Is there a marking on the front side of the pcb for the red circled component?
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Old 03-15-2012, 09:53 AM   #20
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Default Re: Dell 3008wfp faulty power supply

Ahhh...Yes, I can just about read the silk screen using a bench magnifier. The component is definitely D22!

One other question if I may: Do you know if this diode blowing is likely go have damaged anything further down the 14V line (I can't see any fuse or fusible link that would normally be present in a SMPS to protect against such failure, and I'm using the old mains plug from the UPS to power the new 3011, so nothing has blown externally)?

Thanks for your response.

Colin
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