need to know the value of a smd cap

[geep6]

I have a galaxy gts 250 video card given to me and it has no video. But the cooling fan kicks on so i started looking at it closer and i found a piece of smd cap wedged between to legs of an ic. The ic being this one www.richtek.com/download_ds.jsp?s=327 it was wedged between pin 1 and 2 or 2 and 3 not real sure but any way i was wondering if there was a way to tell the value of this cap here are a few pictures of the damaged area

[Toasty]

Re: need to know the value of a smd cap

I think the better question might be... Where are D11 & C465?

Pics on the web don't show them there. See attached. Pure luck to find a pic of that area so clear and large.

If they were not there, then C473 is unnecessary. It connects to nothing.
Looking at the "hanging chad" of a contact, it seems it may have been hit trying to remove/install the board. Perhaps?

What pin does the right hand pad of C473 connect to on the 9259 IC?

Toast

[geep6]

Re: need to know the value of a smd cap

Pins D11 & C465 are not populated on my board either. The right hand pad of c473 goes to pin 1 boot of 9259 IC and the left hand pad of c473 goes to pin 13 phase of 9259 IC.

This is what it says about pin 1 in the pdf. Bootstrap supply for the upper gate driver. Connect the
bootstrap capacitor between BOOT pin and the PHASE
pin. The bootstrap capacitor provides the charge to turn on
the upper MOSFET.

[Toasty]

Re: need to know the value of a smd cap

Unfortunately, SMD caps are unmarked and unremarkable visually. A 1uF may look identical to a 20uF.

Either find a trashed board somewhere or experiment with some values. Maybe start at 1uF to 5uF ?

[tom66]

Re: need to know the value of a smd cap

The bootstrap cap value is not important; 1uF should do. Bigger is better.

[geep6]

Re: need to know the value of a smd cap

Would this cap be directional

[Toasty]

Re: need to know the value of a smd cap

?

You mean polarized? No.

[geep6]

Re: need to know the value of a smd cap

Yea polarized that what i was thinking. Any idea what i might pull one off of. I would hate to have to wait a week to see if it will work. I have all kinds of junk electronics laying around

[Toasty]

Re: need to know the value of a smd cap

Got a cap meter or DMM with a capacitance range?

Again, can't just look at these because two identical could be miles apart in value. Perhaps a power supply or similar area in a piece you have.

[geep6]

Re: need to know the value of a smd cap

I do have a older digital multi meter. But i dont know if it has a capacitance range or how to set it to test for capacitance here is a pic of it.

[Toasty]

Re: need to know the value of a smd cap

Nope. No capacitance scale.

[geep6]

Re: need to know the value of a smd cap

Bummer guess i will just have to order a cap. How much is a decent cap meter ?

[Toasty]

Re: need to know the value of a smd cap

A true capacitance meter would be ~$40 and up into hundreds. A capacitance and ESR meter would be $120+, the latter being the most useful as it does double duty.
The Peak Atlas ESR70 is an example: http://catalog.anatekcorp.com/viewPr...item_id=736034

All Electronics has this one, but I don't know (and won't vouch for) its accuracy or reliability:
http://www.allelectronics.com/make-a...E-METER/1.html

Circuit Specialists has this one (same disclaimer):

Item: CSI6013A -
http://www.circuitspecialists.com/csi6013a.html

They (and others) have DMMs with a capacitance range, but they can be limited in their ranges, such as these:

Item: CSI2010 -
http://www.circuitspecialists.com/lo...ultimeter.html

Item: CSI2205D -
http://www.circuitspecialists.com/csi2205d.html

Item: CSIMS8264 -
http://www.circuitspecialists.com/csims8264.html

I have 2 of the last one as they were "freebies" with orders of equipment.

Their line of meters: http://www.circuitspecialists.com/di...ltimeters.html

Unfortunately, until you step up into bigger bucks, there are few reviews and it's essentially a "pig-in-a-poke" choosing one.

Toast

[severach]

Re: need to know the value of a smd cap

The Atlas ESR70 won't measure lower than 1uF. The cap ranges on a standard DMM work good for this.