SMD capacitor or resistor?? What is it?

Thread Starter

born2fly

Joined Dec 5, 2020
30
I should know better but I'm not sure, sorry if this seems rhetorical. Is there a way to tell if the unmarked(black) components are caps or resistors? I know in most cases they are considered to be resistors but I have also seen were they are caps. This is a dell mb out of a laptop that is missing a few components, keeping it from booting. There aren't any schematics (thank you Dell) so this is a bit of a tricky repair. Thank you to anyone who can help.
 

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MrSalts

Joined Apr 2, 2020
2,111
Ouch. How were they removed? Some look like you can see the tin solder below where the components were. Some look like the tin solder and copper pads were ripped off to leave only the beige circuit board material visible. Those look like someone grabbed the caps/resistors with a pair of pliers and pulled them off. Good luck.
 

DickCappels

Joined Aug 21, 2008
9,105
Generally the ones that are very dark are resistors and the lighter colored ones are capacitors. After a while you will be able to tell upon sight.

When in doubt, desolder the component. Capacitors should have very high resistance.
 

WBahn

Joined Mar 31, 2012
26,932
See if you can match up the silkscreen with the pads. Looks like PRnn is likely a resistor and PCnn is likely a cap.

But what are you going to do even if you can determine which missing components are caps and which are resistors? You don't know what values they should be.
 

Thread Starter

born2fly

Joined Dec 5, 2020
30
See if you can match up the silkscreen with the pads. Looks like PRnn is likely a resistor and PCnn is likely a cap.

But what are you going to do even if you can determine which missing components are caps and which are resistors? You don't know what values they should be.
Exactly - part of my delema. I think all I can do is measure some of the others and hope for the best.
 

Thread Starter

born2fly

Joined Dec 5, 2020
30
Generally the ones that are very dark are resistors and the lighter colored ones are capacitors. After a while you will be able to tell upon sight.

When in doubt, desolder the component. Capacitors should have very high resistance.
The problem is they are missing, seemed to have gotten knocked off when there was an attempt by others to change the battery. Came to me not able to boot, some voltages were present on the board.
 

Thread Starter

born2fly

Joined Dec 5, 2020
30
Ouch. How were they removed? Some look like you can see the tin solder below where the components were. Some look like the tin solder and copper pads were ripped off to leave only the beige circuit board material visible. Those look like someone grabbed the caps/resistors with a pair of pliers and pulled them off. Good luck.
I got the laptop because it wouldn't boot after a battery change & found a few 0402's missing. All I have to go on at this point is a picture of the motherboard online and measuring the existing components & hoping for a good result. I just wanted to be sure I was thinking right on which was what. BTW- I cleaned the pads, you should have seen them before I did, was obvious some of the little guys got ripped. I think someone slipped with a screwdriver because there is a screw hole fairly close by and a scrape nearby that looks like it's from a screw driver. Yeah - this ones gonna be a real challenge, hope I can be a hero with this one.
 

MrSalts

Joined Apr 2, 2020
2,111
I got the laptop because it wouldn't boot after a battery change & found a few 0402's missing. All I have to go on at this point is a picture of the motherboard online and measuring the existing components & hoping for a good result. I just wanted to be sure I was thinking right on which was what. BTW- I cleaned the pads, you should have seen them before I did, was obvious some of the little guys got ripped. I think someone slipped with a screwdriver because there is a screw hole fairly close by and a scrape nearby that looks like it's from a screw driver. Yeah - this ones gonna be a real challenge, hope I can be a hero with this one.
If the copper bands are ripped off and you have no idea which value of which component is needed, your time may be better spent working at McDonalds for $17/hr for 15 hours and buy a new Dell laptop.
https://www.dell.com/en-us/shop/del...aptop/spd/inspiron-15-3510-laptop/nn3510eyzuh
 
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