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Help identifying surface mount capacitor on Dell Motherboard

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211

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I have a Dell Vostro 1500 which suddenly refused to power on. Online searches as well as Dell's 'oh your warranty JUST expired, that's too bad...' tech support point to a bad motherboard.

I pulled the motherboard to see if I could spot anything obvious and sure enough, I found a bad surface mount capacitor. It's labeled PC124 which suggests it's a Power Capacitor but I cannot tell what it's value is. Does anyone have an idea how I can identify what value this cap is?
 

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Preher TV

Member
Remove one of the other caps that is the same color and size and measure it's value. There is a set of 2 more in the photo right above the set that has the bad one. This is going to be the fastest way to find the value of those ceramic chip capacitors.
 

211

Member
I pulled the cap as suggested but I cannot seem to measure any believable values.
I have a Fluke 89-IV which measures capacitance, however with no leads attached I get a value of 0.087 uF (which fluctuates +/- .002uF). When I connect the leads to the cap the value holds steady at 0.088uF, which is pretty much what I'm measuring without the leads touching; I have a hard time believing that is the TRUE value.
I am able to measure a plain 'ol dielectric cap with a stamped value and the Fluke will display its reading just fine.
I'm wondering if the value for the SMT cap is too small or the meter is not sensitive enough???

What are the chances that an 'identical looking' SMT cap from an old desktop mobo would have the same or close enough values?
 
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kchriste

New Member
Forum Supporter
Why is 0.087uF not believable?
No, one that looks simular is not neccessarily going to be the same. Even less likely if it is from another PCB, era, PCB manufacturer, etc...
It is unlikely that the cap is the only problem with your laptop. Change it out to see.
 

Preher TV

Member
What is the capacitance measurement range for your meter?

No don't look on another board, only compare with ones on the same board, and the ones that are in the same type circuit serving the same purpose that are the same size and color.

sometimes it is hard to get a reading from ceramic chip caps, make sure you are pressing down hard enough on the temination caps or use test leads that have sharp tips.

this could be the value, .082uF or 820nF is a normal ceramic chip value, so .088uF would be a normal value found measuring a ceramic chip cap with a tolerance of 10%-20%.
 

mneary

New Member
Your message wasn't clear to me. Did you remove PC125 and measure it? If you can't identify PC125, try PC120, a little further away.

The premise is that if you can identify PC125, it is your best bet to identifying PC124.

What are the markings on that chip next to PC124? I'm guessing it's a MOSFET.
 

mvs sarma

Well-Known Member
What is the capacitance measurement range for your meter?

No don't look on another board, only compare with ones on the same board, and the ones that are in the same type circuit serving the same purpose that are the same size and color.

sometimes it is hard to get a reading from ceramic chip caps, make sure you are pressing down hard enough on the temination caps or use test leads that have sharp tips.

this could be the value, .082uF or 820nF is a normal ceramic chip value, so .088uF would be a normal value found measuring a ceramic chip cap with a tolerance of 10%-20%.

best is to use 0.1 or 100nF

0.082uF makes 82nF and Not 820nF
 

Preher TV

Member
best is to use 0.1 or 100nF

0.082uF makes 82nF and Not 820nF

oops thanks, one place too far...:D..I need to slow down a little bit when stopping in between tasks to reply to posts, and of course I could always use more coffee..lol...
 
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