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What's Q1 on EX475 motherboard? [SOLVED]
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Author:  Fry-kun [ Mon Feb 01, 2010 2:38 am ]
Post subject:  What's Q1 on EX475 motherboard? [SOLVED]
I burned out this component and my LEDs don't work anymore (all except power LED).
It's a MOSFET with "340" written on it -- it's between the VGA header and an electrolytic capacitor, see http://i48.tinypic.com/2d0dv1f.jpg
Can someone help me figure out what that component is?
This page says it might be Fairchild FDV340P (p-ch mosfet 20V 70 mA). I didn't find FDV340P on fairchildsemi.com (nor at mouser and digikey), but there's a FDN340P. No idea if that's the right part though.

If you have a working unit -- I'd like to see a photo of the markings on an undamaged motherboard.
Author:  Rob_Pritt [ Mon Feb 01, 2010 10:59 am ]
Post subject:  Re: What's Q1 on EX475 motherboard?
How did you burn out that component? I've had a similar problem with my MB since upgrading the RAM. None of the LEDs except the power LED work anymore. Plus, the fan speed don't work right either. Sound like I need to pull the MB and examine the components.
Author:  Fry-kun [ Mon Feb 01, 2010 11:33 am ]
Post subject:  Re: What's Q1 on EX475 motherboard?
I think it first burned out by itself at some point. I was trying to diagnose it yesterday and it came to life after burning out some more... don't ask me how that works o_O
But I didn't like it that there was a burnt component in my PC, so I de-soldered it -- LED stopped working again.
Well, here's hoping that someone can help us identify the mosfet so we stand a chance of fixing it...

Could you take a picture of your Q1 (it's on the motherboard between the VGA/Serial header and an electrolytic capacitor nearby). Mine was burned out so I'm not 100% sure I should believe the picture. There seem to be 3 circles in a triangle formation next to the 0 of "340", I'm curious if it's a logo...
Author:  ymboc [ Mon Feb 01, 2010 11:01 pm ]
Post subject:  Re: What's Q1 on EX475 motherboard?
I've had good experiences with electronics repair shops... if it had happened to me I wouldn't hesitate to bring it to the same one that soldered my bios socket.
Author:  Fry-kun [ Tue Feb 02, 2010 1:13 am ]
Post subject:  Re: What's Q1 on EX475 motherboard?
Do you know one in Bay Area that doesn't cost an arm and a leg?
Main problem here is that it's hard to tell what that component was -- that's because these are too small to have very meaningful markings. Once I figure out what it was, I'll get one a solder it into place myself :)
Author:  ymboc [ Sun Feb 07, 2010 10:58 am ]
Post subject:  Re: What's Q1 on EX475 motherboard?
Fry-kun wrote:
Do you know one in Bay Area that doesn't cost an arm and a leg?
Main problem here is that it's hard to tell what that component was -- that's because these are too small to have very meaningful markings. Once I figure out what it was, I'll get one a solder it into place myself :)
I think someone in electronics might be able to tell just by the shape of the component... throw in some of the identifying marks you've already figured out they'll be pretty sure of what you need.

Have you tried soldering surface-mount components? It's a black art... find a dead/old motherboard to practise on, you'll see what I mean.

The other thing to consider is that it might not be the only ruined component on your board... I don't know how much it would cost to repair it in your neck of the woods, but if it's significant you could considering shopping around for a used/refurbished EX47x instead.
Author:  jrock [ Tue Feb 09, 2010 12:33 pm ]
Post subject:  Re: What's Q1 on EX475 motherboard? -- PLEASE HELP WITH PHOTOS
I have it from a reliable source that Q1 is a AO3409 P-Channel Enhancement Mode Field Effect Transistor. Data sheet is here:

http://www.aosmd.com/pdfs/datasheet/AO3409.pdf

Looks like it's in stock at Digikey too for about 51 cents :).

-Jerry
Author:  Fry-kun [ Wed Feb 10, 2010 12:38 pm ]
Post subject:  Re: What's Q1 on EX475 motherboard? -- PLEASE HELP WITH PHOTOS
Jrock, you... rock!
And I like your music taste too ;)

P.S. I'm ordering a 25-pack of these to have some spares and to get a discount. If you want to save a few bucks on digikey shipping, PM me and I'll send you some in a regular envelope (first class USPS) :)
Author:  Fry-kun [ Wed Feb 10, 2010 5:08 pm ]
Post subject:  Re: What's Q1 on EX475 motherboard?
ymboc wrote:
Have you tried soldering surface-mount components? It's a black art... find a dead/old motherboard to practise on, you'll see what I mean.


Actually, yes I have :)
I bought a small SMT soldering practice kit a while ago to test my skillz. My hand is steady enough to do it.. it may not look like a professional job, but it works. Also, I recently ordered a hot air rework station - after I practice a bit on old broken electronics, it should make things even easier.

ymboc wrote:
The other thing to consider is that it might not be the only ruined component on your board... I don't know how much it would cost to repair it in your neck of the woods, but if it's significant you could considering shopping around for a used/refurbished EX47x instead.


That's true, but it's definitely worth a shot for $10. Got 25 replacements for that much, if all is well then I should just need one; if it burns out, I have 24 more tries left :)
If it doesn't work, I'll start asking people to check their signals around this guy.
Author:  Comp1962 [ Thu Feb 11, 2010 2:12 am ]
Post subject:  Re: What's Q1 on EX475 motherboard? -- PLEASE HELP WITH PHOTOS
Check signals around Q1 hell I had to get a magnifing glass just to find it let alone being able to even see well enough to probe around it. One would need one of the round lighted magnifiers just to see what they are doing. I have worked on many boards in my day and would not even contemplate trying to solder one of those suckers on.

I wish you all the luck in the world. :encore:
Author:  Fry-kun [ Fri Feb 12, 2010 3:20 pm ]
Post subject:  Re: What's Q1 on EX475 motherboard? -- PLEASE HELP WITH PHOTOS
Got hot air rework station yesterday and the chips from Digikey this morning. Will probably try installing the replacement tonight.

"Probably" because I have little experience with hot air rework -- I tried desoldering and re-soldering chips off an old busted GPS board this morning, that went fairly well. I'll need to try again a few times before I'm comfortable trying it on a motherboard :)
Author:  Fry-kun [ Sat Feb 13, 2010 12:50 am ]
Post subject:  Re: What's Q1 on EX475 motherboard? -- PLEASE HELP WITH PHOTOS
Just installed it -- no lightshow :(

theory 1: jrock's source is not as reliable as we thought.
The chips I got from digikey have markings A9N̅A / 1H. That makes this part pretty close to 340 and A91̲A / 2D from our photos.. I want to believe that it's the right part.

theory 2: something else on my motherboard is burned out and I have no idea what :(
Author:  Comp1962 [ Sat Feb 13, 2010 2:18 am ]
Post subject:  Re: What's Q1 on EX475 motherboard? -- PLEASE HELP WITH PHOTOS
@ Fry-kun ~ jrock is a reliable source and I do not believe he would post incorrect information. Honestly the difficulty in getting that component installed is a challenge and even if you did manage to get it installed properly without damaging it with to much heat the next issue is without schematics its difficult to trace the lines so your left doing reverse engineering.

Having said all that I also know there is fun in troubleshooting these things and its rewarding when you get it to work. In the mean time I would try to locate a used EX47x somewhere possibly eBay and get your server back running this would allow you to continue to work on your motherboard and run your server or use a known working motherboard to help you troubleshoot your current problem.
Author:  Fry-kun [ Sat Feb 13, 2010 3:21 am ]
Post subject:  Re: What's Q1 on EX475 motherboard? -- PLEASE HELP WITH PHOTOS
Yeah, I think you're right. After checking the datasheets and reading up a bit on FETs, it seem like the part matches up.
Guess I'll be debugging the motheboard :)
Author:  Comp1962 [ Sat Feb 13, 2010 11:25 am ]
Post subject:  Re: What's Q1 on EX475 motherboard? -- PLEASE HELP WITH PHOTOS
There is a test you can do on the actual MOSFET where you set your meter up on the Resistance Scale you can charge the MOSFET with the meter and watch it drain. What I am not exactly sure is if you can do a proper test with it mounted on the circuit board or not but here is a link to show you how to test a MOSFET. http://www.techpowerup.com/articles/ove ... oltmods/21.

Also there are 5 fuses on the motherboard that you should check just incase one of them was taken out. I was looking at them last night on an EX470 Motherboard which works but when it runs the fans speeds are flat and the drive LED's do not come on after the server boots and the health light stays purple. I have not worked on this motherboard in quite sometime but I have 2 motherboards to work on that I pull out from time to time but its been a while but your working with that MOSFET has me motivated to take another look at those 2 boards. One is my original the other I purchased with a known blown LAN port which I actually got to work with a USB to gigibit cable so if I need a motherboard I can use that. Actually the lan port on that particular boad does function but only at 10 not 100 or 1000 and it may not be repairable but I found a way to run it and did run it for a month. Anyway I have 2 EX470 boards that can run in servers but are not fully functional but do work. I would like to make them fully functional again but that might not be possible but I have nothing to lose here.
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