broken Asus motherboard

April 4, 2006 10:02 AM

Help me identify a tiny componant on my Asus motherboard.

I have an Asus A7V333 that I damaged while changing the heat sink. With the help of an electrical engineer friend, I determined that I knocked off the tiny resistor at RN30. If I can find out the values of the component, this friend can easily replace it.

Is there someplace that can help me or from where I can get a detailed schematic/diagram of the board? Asus support is absolutely no help, their online help form is broken, and I get no response to my emails.

posted by bradn to computers & internet (15 comments total)

If it is in fact a resistor, then the answer you are looking for should be quite visible on the outside. The color bands that are painted on it give the value away. Here is the first link that I found via Google, it has the basics covered.

posted by TheFeatheredMullet at 10:18 AM on April 4, 2006

Sorry, here is the link
posted by TheFeatheredMullet at 10:21 AM on April 4, 2006

If it is a surface mount resistor (rectangular, with no wires coming out, as opposed to peanut/cylinder shaped with wires coming out), it won't have color bands on it. Instead it should have numbers identifying the resistance. And be much harder to replace, although if your friend has the equipment it could be possible.

Best bet is definitely to make a thorough search for the lost component. Else I think you have to hope you find someone with the same motherboard.
posted by TheOnlyCoolTim at 10:23 AM on April 4, 2006

Oh yeah - the hardware forums at places like HardOCP would probably find you someone with the same motherboard.
posted by TheOnlyCoolTim at 10:26 AM on April 4, 2006

TFM the resistors with the colored bands are way to larged to be used on the boards.

Does the resistor have any numbers on it?

Why not use a multimeter to measure the resistance of some of the other, similar looking resistors on the board?

And what do you mean by 'damaged'? you could even try mesuring the resistance of the damaged resistor itself.
posted by delmoi at 10:40 AM on April 4, 2006

The resistor itself is gone, there is no way I will find it. It was a surface mount component, not absolutely sure it was a resistor. There are no values except the number on the mobo.
posted by bradn at 11:15 AM on April 4, 2006

I ask this of all you electrical engineering experts: is there any chance that the lack of one resistor wont make any difference? I know that the first inclination is to point out how competitive the motherboard market is, and that no company would spend 1/10th of a cent on an unnecessary component, but couldnt it be that the resistor's function just isnt _that_ important?
posted by Maxwell_Smart at 11:41 AM on April 4, 2006

The "RN" designation may mean that it is a resistor network, that is, several resistors packaged in one part. The value of the resistence may or may not be printed on the part, depending on the size. TheOnlyCoolTim is right, you'll need to find someone with the exact same motherboard to identify the part for you and possibly, to measure the resistence with a meter if it's not printed on the package.
All of this assumes that the pads on the board have not been damaged. If they have, it will take some very specialized skill to repair the pads and solder the part back on.
All of this for a motherboard that is, what? four years old? Sounds like a good excuse to upgrade to me.

btw. you will never get a schematic for the board.
posted by kc8nod at 11:42 AM on April 4, 2006

Ok, thanks.

Yes the component is important, because it won't pass the memory test without it. Incedentally, it's located between the RAM and CPU.

kc8nod, it was an upgrade excuse. I am building a new machine AND I replaced the broken board in the old one with a cheaper version of the same board with less features. I was hoping to still get some mileage out of the broken board. It seems like an easy fix if I could find out what it is, but even to the extent of measuring the component on the replacement board is too much trouble.

Thanks for the help.
posted by bradn at 12:01 PM on April 4, 2006

Maxwell_Smart, I'm not an electrical engineer by a long stretch but it's certainly possible that if the missing component happens to have been part of a non-essential/unused subsystem that it might cause no problem. For example it could be part of onboard sound or video circuitry, an infrared port, a floppy drive interface, or something else that not everyone uses. On the other hand it could be an essential part of memory or hard drive interface circuitry (and could therefore corrupt your data). Or it could be part of some bit of timing or temperature monitoring circuitry (and could therefore cause problems that could damage other components). So the question is: are you feeling lucky?
posted by Songdog at 12:07 PM on April 4, 2006

You can often get away without a capacitor here or there, depending on where it is in the circuit of course. A missing resistor is much more likely to cause a problem - bradn has found that out the hard way :P

If it was a resistor network, it would have more than two connection points, that would be obvious.

If the resistor is attached to a circuit that appears to be repeated, then there is a good chance another copy of the same resistor is already on the board somewhere. Ask for more details if you are interested

There is a good chance that the resistor is just a pull-up/pull-down, or similarly value insensitive. So, you might try soldering a 3k3 or 10k resistor in the location and seeing what happens.

It isn't too hard to solder a through hole component to a surface mount location, just bend the leads so that the component floats above the board. This will not be as reliable as a properly repaired board, but it should be okay. Sometimes it will not work properly at all though, for example the long leads might pick up too much noise..
posted by Chuckles at 12:54 PM on April 4, 2006

If the resistor isnt there a short in the resistor network is created and electricity doesnt flow, which would create a problem. With digital logic circuits often times the absolute resistance values are not that important as many of the chips are designed to operate in a range of voltages (although im not sure how true that is with something as complex as a motherboard).

to adress your question, yes...given lots of time, a computer with circuit software and an EE degree you could reverse engineer the network and figure out the resistance value.

OR you could find someone with a similar mobo and simply measure the resistance of the equivalent resistor on that board...i cant imagine it would be too different from board to board. Then see if doing that works....i have a feeling it will.
posted by I_am_jesus at 12:59 PM on April 4, 2006

If the resistor isnt there a short open circuit (ed.) ... is created.
posted by Chuckles at 1:05 PM on April 4, 2006

thank you chuckles.....

my mind is elsewhere
posted by I_am_jesus at 1:12 PM on April 4, 2006

I probably shouldn't be so pedantic.. If we were talking about an extension cord or something I wouldn't have bothered, but I think it is a little more important when talking about component level electronics.
posted by Chuckles at 1:26 PM on April 4, 2006