Replacing capacitors

ehnde

Thinking about buying a network card for $8 that typically goes for around $100 or more. It's $8 because there is a capacitor missing. Seller has 99% positive feedback on ebay and over 10000 feedback ratings.

On the fence about buying this. Deciding factor is: how hard is it to fix and what should I expect to pay to fix this? Never replaced a capacitor before, but I watched a youtube video Doesn't look hard. I have a soldering iron. Just need the right capacitor from radio shack? I have a soldering iron.

Primarily I'm doing this for geek cred. Grateful for any advice

Devilsbane

If you can find the right size capacitor it is a pretty simple solder job, shouldn't take more than 10 minutes.

Finding which size capacitor is needed would be your challenge. You would probably spend hours looking through documentation. For $8, why not?

tiersten

Why is it missing? If it got ripped out then there may be damage to the PCB traces. If it blew up then there may be damage to other components. I guess $8 isn't much of a risk though...

What type of capacitor is missing? Do you know what value it should be? Its very unlikely to be marked on the PCB itself.

As for soldering it a replacement, it may not be quite that easy depending on how many layers are in the PCB, size of the capacitor, components nearby blocking you and ground planes.

SteveLord

Why is it valued at $100?

demonfurbie

SteveLord wrote: »

Why is it valued at $100?

some of the fiber ones are way over $100

how ever it shouldnt be hard make sure ya have some wick to remove the old stuff before putting on a new one

JDMurray

The first question I'd ask is, "Why is the capacitor missing?" If someone tried to repair the board and did a bad job at pulling the cap, the board is likely ruined (especially true of a lead cap soldered in a multi-layer PCB). If it's a surface mount cap, the PCB could be badly burned if it was removed with a conventional soldering iron.

Find out the current condition of the board and its history, and insist on seeing close-up photos of the area on both sides of the board where the cap is missing. If the board is bad, it might not even have $8 (+ shipping) worth of salvageable parts.

ehnde

Thanks for the advice, I certainly don't want to buy something that cannot be repaired! A picture is worth a 1,000 words, right?

Devilsbane

That spot looks fine, no burn marks or anything.

But what is that off to the right? Looks like a child was stabbing at it with something.

tiersten

Devilsbane wrote: »

But what is that off to the right? Looks like a child was stabbing at it with something.

Looks like adhesive residue from a paper label or something similar. It doesn't look like flux.

tiersten

ehnde wrote: »

Thanks for the advice, I certainly don't want to buy something that cannot be repaired! A picture is worth a 1,000 words, right?

Again, why is it missing? It looks like it was knocked off the board?

Do you know what value that capacitor should be?

You sure that replacing this capacitor will fix it?

It looks like some sort of bypass capacitor connecting one of the internal power layers to the groundplane. It doesn't look like its involved in any regulation, filtering or clock circuitry. Losing it shouldn't completely kill the NIC? You got anything more than just it doesn't work?

ehnde

tiersten wrote: »

Again, why is it missing? It looks like it was knocked off the board?

Do you know what value that capacitor should be?

You sure that replacing this capacitor will fix it?

It looks like some sort of bypass capacitor connecting one of the internal power layers to the groundplane. It doesn't look like its involved in any regulation, filtering or clock circuitry. Losing it shouldn't completely kill the NIC? You got anything more than just it doesn't work?

The listing didn't provide those details. I emailed the seller yesterday. If they don't email back, they don't want to sell the card. You think it could work even without the capacitor? Interesting!

From the auction description:

Because I am not a technician and cannot further test or repair this card, I am selling it AS-IS, without a warranty of any kind.

This was purchased at a live local auction as used, a pull from a good working system.

tiersten

ehnde wrote: »

The listing didn't provide those details. I emailed the seller yesterday. If they don't email back, they don't want to sell the card. You think it could work even without the capacitor? Interesting!

No. I didn't say that and was only basing it on what you said which was that it was a non working card because this single capacitor was missing. It *might* work without it but considering the lack of information, there is absolutely no guarantee that you can make it work again. The lack of warranty and no guarantee that it even works along with the unverifiable status of the card means I wouldn't trust it to work.

TheShadow

I would let it go. If the guy is not a technician then how did he know the capacitor was missing. A simple answer is that he dropped the card on the floor and is now afraid to test it. The surface mount cap cracked and fell off, they are just ceramic and sensitive to g force shock. A second answer is that he plugged it in cocked creating a short and this cap was the first to go. You need to look at the gold fingers then for burning or pitting.

I wish the macro focus on the picture was better as I am not sure that is just sticker adhesive to the right, it could be burning from an internal short. It seems strange that 1) the sticker happened to be next to the missing cap and was peeled off and 2) the guy buys it at a live auction and immediately turns around and sells it when it was supposedly a working pull.

It doesn't pass the smell test to me. Did he buy it for less than $8 dollars as a supposedly working card worth $100. $8 plus your repair time may make it not worth considering. In any case. Cap size is probably the same as the one to the left considering they both take off to bridge etches which disappear to via hole pads. You will need a very fine tip iron and very small gage solder. If the existing tin paste on the pads is lead free then it is going to move around from residual solder paste adhesive. You may need to use a surface mount heat gun used for component removal after pre-tinning the new cap. I still have a vacuum and heat gun removal setup from the days of the motherboard cap fiasco. Not much use for it lately.

ehnde

Eh hardly seems like it's worth it. Think I'll let this one go. Learned a bit about capacitors though

za3bour

Why do you need a network card that is 100$? even if it's 8$ think about all the time you will put into this and it might not work (and I can swear it won't)

replacing a capacitor is super easy if you have the equipment I've done it a lot. I'm not sure about this network card but I remember back in 2001 we had some MB from E-Pox which used to burn almost through out summer.

We only had to change capacitors for them (they would blow) it was cheap and easy process. We ended up of course replacing all of them with MSI

Bottom line, don't buy it IMO