Reusing caps

[Koda]

Guys I would like your opinion on reusing caps from old power supplies and motherboards. The reason I'm asking is because where I am from there aren't many electronics shops and they don't sell quality caps anyways. If I would like to purchase a cap, I would have to travel 45 kms. to the next town, and online shopping is not an option since my country is not approved by PayPal. Also we don't use credit cards alot here. So I have loads of old motherboards and power supplies and I would like to know if you guys think it's ok.

[Topcat]

Re: Reusing caps

its risky business....I'd advise against it, but if you have no alternative, check them with an ESR meter if you can and certainly dont use known bad brands or bloated ones. Beyond that, it's pretty much trial and error.

[severach]

Re: Reusing caps

I've used reclaim caps for a long time. When I started I took everything including the bad brands and 85*C caps. That got my stock up but the bad ones are risky. Some last forever and some die in the cap box. Once I got plenty of good brands I stopped collecting bad brands. I haven't had any problems reusing good brand caps. Reclaim caps must be tested for uf and ESR with a meter like the Atlas ESR70.

One day when stock was overflowing I went through and discarded all my remaining 85*C caps.

A benefit of reclaim caps is that you have a lot of odd shapes and sizes allowing you to service something immediately rather than waiting for an order to come in. Sometimes the best brand with the lowest ESR isn't the best replacement part and sometimes a standard part won't fit. A drawback of reclaim caps is that you never have enough of certain sizes which has driven me to purchase some. Another drawback of reclaim caps is you feel a certain attachment to them and try to conserve. Once you buy a bag full for cheap you are much more liberal about replacing them leading to better quality work.

I will still reclaim a few very good and odd sized caps but as volume rises buying is a lot more practical than reclaiming.

[Spitz]

Re: Reusing caps

Guys I would like your opinion on reusing caps from old power supplies and motherboards. The reason I'm asking is because where I am from there aren't many electronics shops and they don't sell quality caps anyways. If I would like to purchase a cap, I would have to travel 45 kms. to the next town, and online shopping is not an option since my country is not approved by PayPal. Also we don't use credit cards alot here. So I have loads of old motherboards and power supplies and I would like to know if you guys think it's ok.

I have used old caps from motherboards and power supplies for years and most of the time they work. I don't clean the board after I change them so I can tell if they need replaced a second time and 90% of the time if I have to work on boards again, it is not the ones that I replaced. In my opinion I think caps go bad more from heat than anything else, especially in power supplies. The fan locks up without warning and then the caps go bad from the build up of heat. If the ps companies would spend a little extra and put ball bearing fans in their power supplies, it would eliminate over half of the failures.

[cadillacman]

Re: Reusing caps

i save all my "shotgun" caps where i shot it with caps and it didtn fix my issue..

i dont always trust them, but when im in a pinch i use them, also sometimes when im fixing a $20 monitor or cheapie dvd player, spending $10-20 in caps is not cost effective, so thats what they get used for the most.

[onegoodpcguy]

Re: Reusing caps

i save all my "shotgun" caps where i shot it with caps and it didnt fix my issue.

.....

haha i do that too. if you shoot it with new caps they should still be good...??

[Phaihn]

Re: Reusing caps

I fixed my PSU in my Computer with caps from old motherboards and its working ok so far in the long run ill get some good brand caps and redo it sometime.

[cb92]

Re: Reusing caps

I use a white marker to identify used parts. It's handy to mark polarity and to highlight items in photos.

[Uranium-235]

Re: Reusing caps

I only keep known good brands (panny, ruby, some nichi, sanyo), and then test thier resistance curve with an ohmmeter

[PCBONEZ]

Re: Reusing caps

Electrolytic caps 'reform' the thickness of the oxide layer to the applied voltage within an hour.
- The thickness of the oxide layer is what determines the safe voltage for the cap.

That means if, for example, you find a cap with 16v marked on the side in a circuit with only 2.5v actual voltage then it isn't a 16v cap, it's a 2.5v cap.
[That situation is common even on mobos. I've seen 16v caps on actual voltages as low as 1.5v on mobos - it's not even uncommon]

If you then put the [now 2.5v or 1.5v] cap on 12v you will have excessive leakage current [which can damage the cap permanently] and you can end up with a shorted or a permanently high leakage cap.
The cap will try to reform but while it's trying it has excessive leakage - it's a race to see which wins - and you can end up with an uneven oxide layer that has high leakage in some localized thin spots....
[The cap can be handling Ripple just fine but 'leaking' DC to ground - which means your PSU is working harder to keep the voltage in spec.]
.
If you are going to use old caps then you should 'formally' reform them back to the voltage marked on the side.
Especially if you dunno what voltage they were actually on before.

~
Using old caps is much more risky than using new old stock caps.
[NOS = New but past the Shelf Life.]
NOS have only drifted.
Old caps have actually been Reformed down.
.

[stevo1210]

Re: Reusing caps

I've reused old caps from a newer model dead motherboard before. I don't recommend doing it because you're heating the cap off one board and then reheating it again. But I didn't care at the time I fixed a board using old caps from a donor board because the board I was fixing cost $2. That $2 board now sits inside my bedroom computer and hasn't had any issues... yet.

[momaka]

Re: Reusing caps

I, too, reuse caps quite often - even from bad brands. As long as they look ok and the device works "ok", that's all I care about. Of course this is only when I do repairs for my own stuff. If I'm fixing something for someone else, I try not to reuse caps at all if that's an option (or if I am fixing something I care about).

One time, I had some friends of my family bring me a small 17" LCD TV to fix. The problem was with the external power adapter - bad start-up cap. Replacing this cap brought the TV back to life. But since I am curious, I opened the TV anyways. Good thing... I found quite a few bloated 16v 470uF Stone caps on the video/logic board. Didn't have any other caps in stock that would fit, so I reused some Ost RLP pulled from a motherboard. Made note of the bloated caps and gave back the TV. Told them the TV is fixed for now but will need to replace a few more parts again. 3 weeks later I got the replacement caps, took back the TV, and replaced my reused Ost RLPs with proper replacements. TV is still working as far as I know.

Some of the Stone caps I replaced above were not bulged, so I saved them (lol). A few weeks ago, I was experimenting with a flyback transformer and needed a high-frequency AC voltage line to drive the flyback. Decided to use a crappy Sun Pro-built Raidmax 380W PSU - more particularly the unrectified 5V output from the 5vsb. Good thing I decided to try the Raidmax without much load first - the 5vsb went out of spec even with a 100 Ohm load resistor. That's only 0.05A of load! When I tried a 10 Ohm resistor, the resistor that supplies power to the PWM IC started burning and smoking. At first, I blamed Sun Pro and thought it was just crappy design. But then I traced the 5vsb circuit and found that some of the bloated caps on the secondary were for the 5vsb circuit - no wonder the thing couldn't regulate properly. Replaced them with the non-bulged Stone caps above and not only was the 5vsb working, but it didn't go out of spec even with 1A of load.
Hooking my flyback transformer to the 5vsb actually worked, and I guesstimate I was able to get about 2 kV out of it.
Shorting the HV on the flyback made the PSU do some interesting things, though - but that's for another (Sun Pro bashing) thread.

[severach]

Re: Reusing caps

I've had plenty of problems reusing bad brands. Reusing good brands hasn't caused any problems.

[shovenose]

Re: Reusing caps

I have a (somewhat bad) habit of using untested, used, non-reformed, capacitors to fix stuff.
As long as they pass a visual check, I use them.
I keep ALL so I even used Asia'X to fix bulging Fuhjyyus in a PSU even though they are both the same :P
However, I try to use new/quality caps on stuff I sell...

[PCBONEZ]

Re: Reusing caps

Most caps cost well under $1.
Using one bad cap can easily cost an hour (or hours) of your time.
My time is worth more than $1/hr.
.

[stevo1210]

Re: Reusing caps

Most caps cost well under $1.
Using one bad cap can easily cost an hour (or hours) of your time.
My time is worth more than $1/hr.
.

At the time I did my $2 board, the thing didn't even POST. So one night I was bored and decided to recap with some substitute Panasonic ones from another board and amazingly it POSTED. I should probably buy new caps and recap it once more but putting all this work in for a socket 939 board is worthless in my eyes anyway.
If it was a board that POSTed and worked before being recapped then I surely would have bought proper caps to start off with.

[Uranium-235]

Re: Reusing caps

Most caps cost well under $1.
Using one bad cap can easily cost an hour (or hours) of your time.
My time is worth more than $1/hr.
.

not a matter of your time or money. for most of us, we (more specifically customer) wants something NOW. Can't wait for online orders, and sometimes we try to stock new caps, but in the end, occasionally we run into a cap that we don't have new

I just recapped a lcd monitor that had the 'shut off in 2 seconds' issue (dell, of course). In addition a bad screen image (kind of a faded ghost image, an inch off to the right). I replaced 2 elite 16v 1000 with pannys off a asus board, and the 35v 470 elites with some 16v 270 polys from a asus pegatron board. Monitor works beautifully, no ghost image, and actually goes from black to bright probably faster then it would new (something that almost worries me).

one good thing though is I saw radioshack stocking some 25/35v 470 nichicons lately, more expensive then thier general circut caps but totally easy to come by.

and of course you do have somebody in a country that has NO way to get caps, though even paypal is blocked, theres other ways of paying for caps online with other dealers

[gerg]

Re: Reusing caps

I reuse caps if they test good on the esr meter. the company i work for does not believe in anything new

[Uranium-235]

Re: Reusing caps

I just recapped a lcd monitor that had the 'shut off in 2 seconds' issue (dell, of course). In addition a bad screen image (kind of a faded ghost image, an inch off to the right). I replaced 2 elite 16v 1000 with pannys off a asus board, and the 35v 470 elites with some 16v 270 polys from a asus pegatron board. Monitor works beautifully, no ghost image, and actually goes from black to bright probably faster then it would new (something that almost worries me).

hahahah I spoke tooo sooon. Just woke up. Had the monitor off all night, turned on this morning. yay, works great. Had it on for a few seconds.........POP!!

turned it off, unplugged it post haste. kind of happy this happened now, and that I didn't keep it on all night testing the screen

loudest pop i've ever heard from electronics. Didn't effect the monitor screen for the few seconds it was on after the pop, sssmeelled. Not a lytic smell ether, so I suspect I popped a poly. Maybe I should stick to lytics in these cases. I was going by the half rule since it is a vrm, though a power supply vrm, not CPU. I'm going to take it apart and post a pic in a few hrs

smell reminds me of burnt popcorn, in itself some what ironic

[PCBONEZ]

Re: Reusing caps

At the time I did my $2 board, the thing didn't even POST. So one night I was bored and decided to recap with some substitute Panasonic ones from another board and amazingly it POSTED. I should probably buy new caps and recap it once more but putting all this work in for a socket 939 board is worthless in my eyes anyway.
If it was a board that POSTed and worked before being recapped then I surely would have bought proper caps to start off with.

What does that have to do with using a bad cap?
.