Can this motherboard part be replaced

[davexnet]

Hello,
It's a last-ditch effort to see if I can repair this old motherboard.
A small black component (I think it's a power regulator of some kind) has burned out
along with 2 capacitors next to it. I've changed the capacitors but it wasn't enough.

It looks as if it may be beyond the typical home repair; this part seems to be attached to the
board in a pretty sold way, perhaps to draw of the heat.

Here's a stock image I found showing similar parts, I marked them with a red hand-drawn
arrow, lower right.

Any thoughts appreciated.



Uploaded with ImageShack.us

 

[jomeshkck]

Hello,
It's a last-ditch effort to see if I can repair this old motherboard.
A small black component (I think it's a power regulator of some kind) has burned out
along with 2 capacitors next to it. I've changed the capacitors but it wasn't enough.

It looks as if it may be beyond the typical home repair; this part seems to be attached to the
board in a pretty sold way, perhaps to draw of the heat.

Here's a stock image I found showing similar parts, I marked them with a red hand-drawn
arrow, lower right.

Any thoughts appreciated.



Uploaded with ImageShack.us

This is MOSFET may be N-Channel, if it burned you can change it use a hot air soldering station, if this board is a pb(lead) free, you need an extra preheater unit.

If it is make before 2007, the board may use pb+sn solder. so you can use only hot air soldering station. But pb is poison never soldering in a closed room.

 

[davexnet]

The board is old, I'm unable to see any identifying info on the part at all.
Should it be a certain voltage or value?

If it can be identified, or it's just a generic part, can you suggest a possible source
for a new part?
Thanks again.

 

[jomeshkck]

Which one is burned or Both are burned? You are denoted two arrows.
Is it your burned mobo?
I can't see properly in photo..

 

[jomeshkck]

Ok, I hope it for memory power section.
You can change both are with N-Channel MOSFET TO-252, 30V/24V,60A, Below 15mOhm.
STD70NH02LT4 or NTD60N02R would be better:thumbsup:.

 

[davexnet]

Actually, that's not my motherboard, just a stock photo to illustrate the parts.

On the actual board that's burned out, there are two next to each other. The other one
looks OK and there is lettering that I can see. I'll see if I can get a magnifying glass
and ID further.

Location-wise, they are next to the power supply main connector, also close to the RAM
slot.

Thanks very much for your help.

 

[davexnet]

I got this component off. It seemed to be glued to the board.
Is this some kind of thermal compound? The legs 2 were unsoldered easily enough,
but the part was attached to the board on the side opposite the legs. The base
seems to be partly metallic, not sure if there is an electrical contact in the base, or
whether it's purely for heat transference.
The writing on the part says as follows:
ST 9918
MOROCCO
B4ONE
03L-20

Unless those numbers mean anything to anybody, I'll see what I can find re:
the info given earlier.
Thanks very much.
Dave

 

[davexnet]

This is the part number.
If anybody knows a source, I'd appreciate it.

STB40NE03L

Thanks.

 

[C1]

Not optimistic at all about doing the proposed repair on a multi-layered board. As has been pointed out on other threads, if you want to take a chance on replacing soldered in components, then let a competent TV repair service attempt it.

I dont see the MB model number provided, but there's an outstanding chance you can still buy a good used replacement board perhaps even for less than the price of the components you intend to replace.

 

[bryanl]

This is the part number.
If anybody knows a source, I'd appreciate it.

STB40NE03L

Mouser, Digi-Key, RS Components, Farnell, Allied Electronics, Future Electronics are some suppliers. The manufacturer is http://www.STmicro.com

You do not need an exact replacement, just something with voltage, current, and power ratings at least as high as the originals and the operating characteristics being similar, especially the Vgs(th) gate-source threshhold voltage of 1.4V and the Rds(on) drain-source on-resistance not being in excess of 14 milliohm.

Watch the packaging type or else the replacement may not fit.

The original device was not glued to the circuit board, but its metal tab was soldered to the board. Use conventional leaded solder (60% tin, 40% lead).

 

[C1]

And when installing, dont overheat the component. Use appropriate heat sinking.
http://www.instructables.com/id/Save-your-components-with-a-heat-sink/

Be sure to not damage the MB at the solder points because of overheating.

 

[bradley]

And when installing, dont overheat the component. Use appropriate heat sinking.
http://www.instructables.com/id/Save-your-components-with-a-heat-sink/

Be sure to not damage the MB at the solder points because of overheating.

Why are all the best ideas so obvious, after the fact? lol I'm going to have to try this.

 

[davexnet]

Hi all,
thanks very much for the tips. It's an old board from an old PC (1999)
running Windows 98/Win2k dual boot. We only keep it around because my wife
does some basic home bookkeeping on it, and a few old games in Win 98 my kids play.
The board is an Epox MVP3G-M. If the fix fails, I'll just save the important
data and put something else together - let's be honest the board has had
a good life, used almost everyday for 12, 13 years.

I contacted Digi-key, and they sent me some information. The part is not available,
but they mention a possible alternative. I'm going to give it a try .
The part is only 76 cents.
http://www.digikey.com/product-detail/en/SPB42N03S2L-13/SPB42N03S2L13INCT-ND/593314

I'll update the thread when I've performed the necessary surgery on the board.
Thanks,
Dave

 

[davexnet]

I got the mosfet soldered in. I found it tricky, not a lot of room, close to other
components etc,etc. The PC actually powered up, where it didn't before.
However, with in 30 seconds it was obvious something was wrong, this new
component and the mosfet next to it were very hot and it was obvious if I left it on
any longer it would burn up.

NO obvious signs of any other damaged parts on the board. I've given up with it,
it's too old to spend any more time. Still, interesting exercise.

 

[C1]

Thanks for the report concerning how the job turned out (most people dont do that).

Ya, I was pessimistic regarding replacing the obvious defective components. My personal experience is that some circuit issue caused what one actually sees and thus what you see is the result not the actual cause.

You probably could buy a working version of that MB off eBay for little cost, but I dont think that you actually need an exact replacement. An old vintage board hosting a BX chipset probably would do.