electronics, repairs, service manuals and datasheets discussion community for the repairs professionals and technicians
FAQSearchMembersGroupsRegisterProfilePM'sLogin/Out
Dell 2405fpw LCD - need "common" equivalent part

 
Post new topic   Reply to topic    Electronic equipment repair and service manual search discussion Forum Index -> Equipment Repairs
View previous topic :: View next topic  
Author Message
matthewy



Joined: 24 Dec 2008
Posts: 14

PostPosted: Tue Oct 27, 2009 8:47 am    Post subject: Dell 2405fpw LCD - need "common" equivalent part Reply with quote

Hunting down an issue with a dell 24" lcd monitor. Looks to be that the mosfet - 5305S has died and also took down one of the zener diodes near by.

I'm trying hard to find a common replacement for the mosfet but the specs indicate its a "Hexfet". Never seen a hex fet before. Looking for help as to what might be a suitable replacement (http://www.irf.com/product-info/datasheets/data/irf5305spbf.pdf).

Other issue is that the zener diode is burnt beyond recognition. It joins the Gate to ground in reverse direction ) Gate -----|<|----- Ground. Is this diode just for protection, anyone recomend a replacement for this too (or better yet has access to teh dell schematics? Was hoping the datasheet for the IRF5305s would have a sample with the diode in place but no luck Sad

Any help greatly appreciated, would love to get this guy back up and working, even has composite inputs etc Smile
Back to top
View user's profile Send private message
matthewy



Joined: 24 Dec 2008
Posts: 14

PostPosted: Tue Oct 27, 2009 10:12 am    Post subject: Reply with quote

just incase anyone does have the scvhematics, the zenar is D19 Smile
Back to top
View user's profile Send private message
linear



Joined: 01 Jan 2010
Posts: 1

PostPosted: Fri Jan 01, 2010 7:42 pm    Post subject: Reply with quote

Same problem here on a Dell 2405FPW, FET IFR5305S shorted, along with D19 Zener.

I've found the International Rectifier FET on eBay and locally.
Haven't tried to remove or identify zener D19 yet.

Perhaps D19 is identical to D18 (in a similar SWPS circuit right next door).

Did you succeed with your repair?
Any more info would be appreciated.

Happy New Year. Smile
Back to top
View user's profile Send private message
soumen
Guest





PostPosted: Thu Mar 08, 2012 6:47 pm    Post subject: 2405FPW D19 zener Reply with quote

Same problem here badcaps.net/forum/showthread.php?p=222789. D18 looks like a 3V zener, but no particular reason why D18 and D19 should be identical. Unfortunately, powering this up with a wrong zener may kill parts downstream. Any progress on figuring out what D19 is?
Back to top
chappers



Joined: 21 Feb 2012
Posts: 3

PostPosted: Thu Mar 08, 2012 10:23 pm    Post subject: Reply with quote

The zener, if connected between source and gate, is there to reduce damage caused by MOSFET failure, because often MOSFET failure results in a short-circuit between drain and gate, putting drain voltage on the gate, and thus back to the gate drive circuitry, causing much damage.

A zener of the right value will protect the drive circuitry. If a similar MOSFET is using a 3V zener, then that may well do for D19 too, if they are operating with similar gate voltages. You will not damage anything by using the wrong zener as it's there for protection if the MOSFET fails.

In fact, you could run the monitor without D19. Try it. Measure the voltage on the MOSFET gate using a 3V zener and if the MOSFET connected to D19 uses approximately the same voltage, then put a 3V one there.

Let us know how things go, because lots of people from my googling seem to have come across this same fault and don't know what D19 should be.
Back to top
View user's profile Send private message
soumen
Guest





PostPosted: Fri Mar 23, 2012 7:28 am    Post subject: 2405FPW D19 zener Reply with quote

The IFR5305S drain should be at 5VDC. I measured this from a properly working monitor. This means a 3V Zener is incorrect. Use at least a 6.8V Zener which should be quite safe for downstream parts. I managed to supply 5V to the drain (after removing the burnt FET) from an external 5V SMPS and all works well. I am not sure I want to replace the FET, for fear that the gate controller logic may be fried. I also recapped the SMPS board, and it is sending 19V and 7V to the other boards as is normal.
Back to top
Display posts from previous:   
Post new topic   Reply to topic    Electronic equipment repair and service manual search discussion Forum Index -> Equipment Repairs All times are GMT
Page 1 of 1

 
Jump to:  
You can post new topics in this forum
You can reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot vote in polls in this forum


eServiceInfo on FB - Service Manuals Free Download - Service Diagrams

Free TV Schematics Download - HARDW.net - Pinout Master - Jabse Service Manual Search - Jabse.InK  - onTap.bg

SnimkiOt.com - Poblizo.com : пътешествия