Dell 3008wfp faulty power supply

gajones · 04-13-2011, 09:56 AM

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.

**Scenic** · 04-13-2011, 10:05 AM

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

datasheet
http://bambooz.pytalhost.net/badcaps..._datasheet.pdf

**retiredcaps** · 04-13-2011, 11:36 AM

findchips.com

http://www.findchips.com/avail?part=V30120S

zen · 04-13-2011, 12:21 PM

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

**Th3_uN1Qu3** · 04-13-2011, 12:42 PM

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.

**multimeter** · 04-13-2011, 12:45 PM

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.

**Th3_uN1Qu3** · 04-13-2011, 03:34 PM

^^ 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.

**alexanna** · 04-13-2011, 03:50 PM

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?

zen · 04-18-2011, 10:27 AM

thanks for the input guys

will have another go at it.

gajones · 07-03-2011, 03:42 AM

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?

ezdy · 07-04-2011, 02:33 AM

Quote:

Originally Posted by gajones

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...

gajones · 07-04-2011, 02:25 PM

Quote:

Originally Posted by ezdy

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?

**Lumberjack777** · 07-31-2011, 05:01 PM

Quote:

Originally Posted by Th3_uN1Qu3

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.

**Lumberjack777** · 08-16-2011, 08:15 PM

Quote:

Originally Posted by Lumberjack777

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.

**Th3_uN1Qu3** · 08-17-2011, 05:22 AM

Thanks for the report! We're always happy to hear success stories.

mardon1975 · 01-12-2012, 05:15 PM

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.

**retiredcaps** · 01-12-2012, 05:23 PM

Quote:

Originally Posted by mardon1975

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.

Jetset · 03-14-2012, 07:51 PM

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.

**retiredcaps** · 03-14-2012, 10:19 PM

Quote:

Originally Posted by Jetset

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?

Jetset · 03-15-2012, 09:53 AM

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

04-13-2011, 10:05 AM	#2
Scenic o.O Join Date: Sep 2007 City & State: Duisburg My Country: Germany Line Voltage: 230VAC 50Hz I'm a: Hobbyist Tech Posts: 2,619	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 __________________

04-13-2011, 11:36 AM	#3
retiredcaps Badcaps Veteran Join Date: Apr 2010 City & State: Canada Posts: 9,165	Re: Dell 3008wfp faulty power supply findchips.com http://www.findchips.com/avail?part=V30120S __________________ --- begin sig file --- If you are new to this forum, we can help a lot more if you please post clear focused pictures (max resolution 2000x2000 and 2MB) of your boards using the manage attachments button so they are hosted here. Information and picture clarity compositions should look like this post. We respectfully ask that you make some time and effort to read some of the guides available for basic troubleshooting. After you have read through them, then ask clarification questions or report your findings. Please do not post inline and offsite as they slow down the loading of pages. --- end sig file ---

04-13-2011, 12:21 PM	#4
zen New Member Join Date: Apr 2011 Posts: 2	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

04-13-2011, 12:45 PM	#6
multimeter Badcaps Veteran Join Date: Jan 2011 City & State: devon My Country: united kingdom Line Voltage: 230v 50hz I'm a: Hobbyist Tech Posts: 738	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.

04-13-2011, 03:34 PM	#7
Th3_uN1Qu3 Believe in Join Date: Jul 2010 City & State: Bucharest My Country: Romania Line Voltage: 230VAC 50Hz I'm a: Professional Tech Posts: 5,368	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.

04-13-2011, 03:50 PM	#8
alexanna Member Join Date: Mar 2010 City & State: st.louis mo Posts: 1,300	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? __________________ Whatever I do, I consider it a success, if in the end I am breathing, seeing, feeling and hearing!

04-18-2011, 10:27 AM	#9
zen New Member Join Date: Apr 2011 Posts: 2	Re: Dell 3008wfp faulty power supply thanks for the input guys will have another go at it.

07-03-2011, 03:42 AM	#10
gajones New Member Join Date: Apr 2011 Posts: 4	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?

08-17-2011, 05:22 AM	#15
Th3_uN1Qu3 Believe in Join Date: Jul 2010 City & State: Bucharest My Country: Romania Line Voltage: 230VAC 50Hz I'm a: Professional Tech Posts: 5,368	Re: Dell 3008wfp faulty power supply Thanks for the report! We're always happy to hear success stories.

01-12-2012, 05:15 PM	#16
mardon1975 New Member Join Date: Jan 2012 Posts: 1	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 05:23 PM..

03-15-2012, 09:53 AM	#20
Jetset New Member Join Date: Mar 2012 City & State: Yeovil, Somerset My Country: U.K. I'm a: Knowledge Seeker Posts: 10	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