Change Capacitors On Motherboard

[hackmole]

I have a bad humming noise on dialup and have been told that the problem is my capacitors on my Dell motherboard and that one or more need to be replaced. The capacitors I have are by Sony 3900mf, 6.3v. Does anyone have any recommendations of what capacitors might be best to get or anything else to say about that problem?

 

[KF]

Who is it that told you this? Do not change the capacitors on your motherboard.

A bad capacitor in a non-switching power supply could cause hum. But they don't use that type of power supply in PCs. Devices that hook up to the PC may.

The dial tone is a sort of humming noise. Is that what you are talking about? Some modems have a setting to check for a dial tone (or not) before they dial.

It is more likely hum has something to do with the way the phone line is hooked up or improper or missing ground. For things that attach to the computer, if they have electrical plugs that are not polarized, try reversing them.

 

[hackmole]

Thank you for your respionse.

The humming sound is not the dialtone sound. It is a humming sound in the background of the dailtone sound. And it comes in either high frequency or low freqency and slows my Internet speed to a crawl.

I also have a second computer and with the same connections, same wires, and same modem have no problems. I have already changed the power supply box with no change. I used a different phone and still had no change. I also notice that there is a wire from my motherboard to the frame which I guess is the grounding.

A tech support person thinks it is the capacitors that either might have blown out from a powersurge or lightning or were just bad.

 

[jamautosound]

Since you have the same modem in another computer, try swapping those, just to count out the fact that it's not the modem.

Before you start changing capacitors.

 

[hackmole]

Sorry, that's what I meant about the modem. I swapped the modem from my other computer, the computer I'm using right now, and transferred that modem to the other computer and got the bad dialup noise. I also moved the computer to a different spot in case there might be something interferring but that didn't make any difference. I used a different surge plug adapter but that didn't make any difference either. I keep on thinking if there is something I overlooked but I don't believe bad RAM could be responsible for line noise. It seems like the only thing left is the motherboard or the capacitors. And bad capacitors have been known to cause dialup noise. Somewhere I also read that not enough capacitors on the motherboard could cause dialup noise. If I had a volt meter I might be able to check and see which capacitors were bad but I don't so I think I would have to change all eleven capacitors on the board. I think the capacitors are pretty cheap but the labor could be intense because those capacitors are bolted on the board and I would have to use a soder gun and melt their stubs off. Then I would have to melt the new ones back on. I don't know if it is even going to be worth all the trouble.

 

[OS]

Originally posted by: hackmole
Sorry, that's what I meant about the modem. I swapped the modem from my other computer, the computer I'm using right now, and transferred that modem to the other computer and got the bad dialup noise. I also moved the computer to a different spot in case there might be something interferring but that didn't make any difference. I used a different surge plug adapter but that didn't make any difference either. I keep on thinking if there is something I overlooked but I don't believe bad RAM could be responsible for line noise. It seems like the only thing left is the motherboard or the capacitors. And bad capacitors have been known to cause dialup noise. Somewhere I also read that not enough capacitors on the motherboard could cause dialup noise. If I had a volt meter I might be able to check and see which capacitors were bad but I don't so I think I would have to change all eleven capacitors on the board. I think the capacitors are pretty cheap but the labor could be intense because those capacitors are bolted on the board and I would have to use a soder gun and melt their stubs off. Then I would have to melt the new ones back on. I don't know if it is even going to be worth all the trouble.

You need to examine the capacitors on the mobo. It will be plainly visible on the mobo if the caps are really going bad. If the tops are puffing up and/or cracked, or if they are leaking fluid, then the caps are bad. If you don't see anything, the caps are fine.

If in fact the caps are bad on the mobo, consider just replacing the mobo. It's pretty time consuming to replace all the caps and if you mess something up, you can cause damage to other stuff in your computer.

 

[AMDfreak]

I agree that a new mobo is the better option, but just in case you really need to keep that one, here is a guy that will replace capacitors for you.

 

[hackmole]

Thanks, that is a good web site. It's hard to be there are people who actually do that. Seems really hard.

 

[KF]

Originally posted by: hackmole
Thank you for your respionse.

The humming sound is not the dialtone sound. It is a humming sound in the background of the dailtone sound. And it comes in either high frequency or low freqency and slows my Internet speed to a crawl.

I also have a second computer and with the same connections, same wires, and same modem have no problems. I have already changed the power supply box with no change. I used a different phone and still had no change. I also notice that there is a wire from my motherboard to the frame which I guess is the grounding.

A tech support person thinks it is the capacitors that either might have blown out from a powersurge or lightning or were just bad.

From what you say, it does seem like the computer is the source of the noise. I don't think there is any assurance that changing the big capacitors would fix it, although I suppose it could. Computers generate a lot of electical noise, but normally that doesn't affect the modem, since they are designed to operate in that environment.

Another possibility is to use an external modem.

The noise changes pitch from low to high, is that right? Does it ever go away? Has the modem ever worked right with this motherboard?

One thing easy to do is to loosen and retighten all the screws that hold down the mobo any other screws. The idea is to assure a good ground, which reduces electrical noise.

Are you using the same monitor with both computers? Is there anything else that is different between the two setups?

 

[hackmole]

The noise changes pitch from low to high, is that right? Does it ever go away? Has the modem ever worked right with this motherboard?

Not exactly. The noise on dialup is either a low pitch humming or a high pitch humming but it doesn't change from low to high or high to low during dialup. And it only goes away once I am logged in to my isp. But then I get horrible slow speed and sometimes completely freeze out on a Web site. And the modem has never worked right with that computer.
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One thing easy to do is to loosen and retighten all the screws that hold down the mobo any other screws. The idea is to assure a good ground, which reduces electrical noise.


I did remove the motherboard at one point. The one screw it had was pretty tight.
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Are you using the same monitor with both computers?

Yes, I'm using the same monitor for both machines and use a straight connection though I could use a switchbox so I wouldn't have to unplug and replug every time.
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Is there anything else that is different between the two setups?

Yes, they are two different computers. The one I'm using without the noise has the TX-proII motherboard while the one that includes the noise is from the Dell Optiplex, motheboard made in Taiwan. The one I'm using has a separate soundblaster sound card and a separate ATI video card while the Dell Optiplex has the sound card and video card built right in to the motherboard.

 

[KF]

It looks to me you did everything reasonable with the equipment available to you. You can't change the sound or video. And anything you do is going to cost money. You'd have to love that Dell mobo pretty good to put $50 into it.

If that Dell machine is otherwise acceptable to you, you could go with an external modem.

USB modem

SupraMax,56K V.90, USB,Modem,External. with drivers $29

 

[Hamburgerpimp]

$50-$75 to change capacitors? Just buy a new or refurb mobo for half that and be done with it. You may have to reformat if your Dell is a proprietary mobo.

 

[neo4s]

You cannot always tell if a cap is bad simply from looking at it. Even if they look normal, you?ll still have to check them with a cap checker, meter, or o-scope to be sure. Is the phone line next to any electronic equipment? Transformers in electrical equipment can induce AC noise into nearby lines. Sounds like you?ve checked about everything and might be down to either repair or replacement. IMHO just spend the extra few dollars and upgrade to a new mobo.

 

[hackmole]

I know that you can't tell if a capacitor is bad just by looking at it which is why I'm going to take all 11 of them out and replace them. I took one out yesterday but it wasn't that easy. The problem is that I couldn't pull it out by the stubs. So I ripped a capacitor off but the stub is still there. I'm not sure if I should try to remove the stub or just glue a new capacitor on to it.

If I got a new motherboard, I am not so sure it would fit in this optiplex case because this case also came with a daughter board. So I'd probably have to buy a new box. Then I would probably also have to upgrade my power supply because I think the new processors use more power. Then I'd probably also have to buy a new Pentium IV processor. And with the new motherboard, I'd also have to buy the newer ram instead of the older Dimms and Simms which I have a lot of and which would go to waste.

I definitely need a better board than my current Techpro II which only supports an 8 gig drive because I don't like that Maxtor Maxblast software I have to use so it will recognize more than 8 gigs since I have a 60 gig drive. But the Optiplex board supports up to 100 gig drives without any extra software.

Mostly, I'm more interested in spending my money on a wireless network card and access point so I can hook in to a local wireless ISP. I'd love to have super fast downloads.

 

[neo4s]

You ripped the capacitor off the board?!? :Q Capacitors should only be removed by de-soldering, and on a motherboard it should be done very carefully by an experienced electronics technician (like myself). You cannot glue on a new capacitor. The only chance you have of saving the board now is to bring the board (and the capacitor!) to an electronic tech and let him try to fix it. To replace one cap I would charge about $20, to change 11 caps I would probably charge about as much as the cost of a new board? that?s just me though. Whatever you do, don?t pull anything else off the board. Also your computer system sounds like it?s seen its better days. It wont do much good to have blazing fast downloads if you run out of room on your hard drive. I think with the age of your computer and the cost of repair you should seriously consider a new computer.