The only reason to buy old stock is to save money. They aren't rated for long term storage and they do have a finite shelf life. Buying fresh through regular channels I also know I'm getting genuine stuff and not some fake crap.

Ozzuneoj wrote:

I have a question for everyone who tinkers with old hardware and on occasion has to replace capacitors.

I am mainly talking about electrolytic caps.

TL;DR response from me - I'm in the camp that checks physical cap condition and replaces if they look bad and/or checks brand names and replaces on brand alone. And yes, sometimes I just flat out replace because preventative maintenance. When I do replacements, I do a full recap because why not? Especially if the brands aren't reputable. Chances are a board that has 15+ year old electrolytics aren't going to be the best.

Its a basic question. If any of us can dig a 10-30 year old computer out of a scrap heap, power it on and NOT have capacitors explode or have the system immediately become unstable, why do some people make such a big deal about buying New Old Stock capacitors?

New old stock capacitors? Why on earth would people do that? Buy new Japanese caps from Nichicon, Panasonic, Rubycon, or Chemicon.

I've read about people building "capacitor reforming" stations out of breadboards and laptop power adapters to "heal" the capacitors because of film layers degrading over time etc. etc. etc....

Do you have some sources for this and the context for what types of caps they are healing?

And all that sounds perfectly reasonable, but why don't we see the effects of capacitors sitting unused for years in our various devices?

The phrase "see the effects" actually refers to a broad range of what can be observed.

A cap responsible for noise filtering for power on your mobo could be letting noise through that it should otherwise eliminate. Would you notice this if not looking for it on a multimeter or oscilloscope? Maybe not. But then maybe it gets bad enough to start causing noticeable oddities in the circuit it supports.

Perhaps there are capacitors in a sound circuit that aren't in the best of shape and the color of the sound changes - or maybe it is in the amp circuit and you just shrug and turn up the volume. "No biggie."

Maybe there are some failed caps in your power supply that are not doing their job. Maybe the PSU powers up just fine, but the caps inside have gone bad. Etc... etc...

The changes in the values for the caps as they age can still easily be within tolerance for the circuit they support. So it isn't that the what-ifs above are meant to cause paranoia. They are simply what ifs. Things to keep in mind when evaluating your hardware.

Some would have you believe that a 5 year old "New Old Stock" cap of a reputable brand isn't worth using to get a 17 year old motherboard working...

What's with the new old stock?

and yet the rest of the caps on the board that aren't leaking likely won't explode or cause problems of any kind if you do replace the bad one.

That doesn't make sense. Do these "some" work on the premise that the best time to replace a capacitor is after it vents? (More on "explode" in a bit)

Some people take things so far that they replace every single capacitor on every board or power supply they get.

If I am using an old power supply in the long run for an old system I just built, I recap it. For motherboards, I suppose you can play it by ear - but the chances are that mobos from a certain time period need a recap regardless. Also, the support caps near the processor especially are low ESR. As caps age, their resistance can increase. Then you start getting into that territory of works sometimes or "Hmm... it didn't start up on the first try once last week, but now it is OK..."

Others, like me, replace only bad\leaky caps and use TONS of old gear with the original caps and have no issues what so ever.

The #1 terrible assumption I see people make (and right here on vogons) is that the only caps that are bad are the ones that are leaky. You can't tell if a cap is good by looking at it. In addition, sometimes the caps leak out the bottom rather than vent at the top - in which case they did visibly leak, but the leakage might not be seen prior to removal. So when you say "bad/leaky" - do you mean only those that are leaky or that you pull caps out of circuit and test them to see if they are bad?

The devil's advocate response that ties into what I said earlier, though - you could have a capacitor in TERRIBLE shape and things still operate just fine. It comes down to when you want to address caps - is it a preventative maintenance operation, or do you want until something starts failing?

My IBM 5150 has all its original caps.

Those are tantalum caps. Apples and oranges to electrolytics. This is also what I was assuming you meant when you mentioned exploding capacitors earlier.

All of the OEM Slot1 and Socket 7 boards I have tested from the mid 90s have zero bad caps and work perfectly,

You pulled every individual capacitor and tested it with an ESR meter? Wow. 😁

despite being in storage for 10+ years and probably not used much for 15 or more (with the caps themselves being 20+ years old).

So, why should I avoid large lots of obviously legitimate (not fake) brand new capacitors on eBay just because they weren't manufactured this year or even from within the last 10 years? I know the scientific reasons, but how many of you actually experience repeated failures of older high quality capacitors?

You'll have to explain the new old stock reasoning to me, because I don't follow. I mean I know that certain lines of caps are being retired and some values are being dropped (for instance I had to sub some 2.2uf caps for 1uf caps for the PSU I just recapped), but I don't see a reason to buy OLD capacitors.

I will say that if I do bother to actually purchase new capacitors and spend the time to do a re-cap, I
1: Buy Japanese
2: Buy from a reputable source like Digi-key or Mouser. I will never buy caps from ebay. Ever.

All I meant by "new old stock" is, not brand new from Mouser or Digi-Key. For example, a big bag of Sanyo WX capacitors 200 count for $20:
https://www.ebay.com/itm/CAPACITOR-RARIAL-150 … vAAAOSwyP5Z57Xt

New package, packing slip, style of capacitor matches all the pictures online so it isn't likely to be fake. But the date is from 12 years ago.

I'm sorry if my post came across as critical of those who are more diligent at replacing and testing capacitors, its just frustrating trying to find consistent sources online for inexpensive parts and information about what we should or shouldn't bother replacing.

When I mentioned not replacing all capacitors on a board, I meant that most people seem to ignore all of the very small electrolytics on a board and only replace the larger ones that more commonly fail. I will always replace all caps of a certain brand on a board when I recap due to failures, but if there are caps of other (better) brands that I don't currently have replacements for, if I test the system and it works, I don't generally replace those. So, at what point is it actually important to replace a capacitor? How old? How big or small? What location?

And no, I don't have an ESR meter. At some point you have to have limits on what you can reasonably call defective and worth replacing. It depends on your level of knowledge\skill (mine is fairly low), tools available (I have soldering\desoldering stations and a basic multimeter), and the reliability of the device (in my case, most things "seem" to me to work fine unless visibly defective). I just don't personally have the skill, equipment or time to pull, test and replace every cap on every board I come in contact with that is more than 10 years old. For the most part, this has suited me just fine and I've been playing with old hardware for years (built my first K6-2 Voodoo 2 SLI Win98 system in 2007 and its still working). I'm sure things will continue to age differently as capacitors in PCs approach 30-40+ years old, but the components I have dealt with up to now have so rarely had ANY recurring problems that I haven't even seen the need to get a tester for capacitors. Also, while I agree that seemingly infrequent problems could be related to aging capacitors, its hard to use the stability of older PCs as a gauge for determining whether it should be recapped. Systems used to crash all the time, even when new 😀. Anandtech used to actually keep track of how many crashes they experienced in a certain time period on a given platform.

My IBM 5150 does have electrolytics in its power supply, and that's what I was referring to... sorry, should have clarified. The system is jam packed full of extra hardware and it "seems" to still be working fine, despite the 30 year old 63 watt unit that sat completely unused in storage for 15 years before I got it. I may recap it at some point, but I need to get a special screw driver to get into the PSU, as it uses security torx or some crazy thing like that. I did replace a bad tantalum on a NOS Everex EGA card though. 😀

Anyway... this is an interesting discussion, I hope to learn more about all this stuff eventually.

The manufacturer will have shelf life information, although that will be based on both electrical viability and usability in soldering processes.

If you like, here's some reading for you...
http://citeseerx.ist.psu.edu/viewdoc/download … p=rep1&type=pdf

Ozzuneoj wrote:

All I meant by "new old stock" is, not brand new from Mouser or Digi-Key. For example, a big bag of Sanyo WX capacitors 200 coun […]
Show full quote

All I meant by "new old stock" is, not brand new from Mouser or Digi-Key. For example, a big bag of Sanyo WX capacitors 200 count for $20:
https://www.ebay.com/itm/CAPACITOR-RARIAL-150 … vAAAOSwyP5Z57Xt

New package, packing slip, style of capacitor matches all the pictures online so it isn't likely to be fake. But the date is from 12 years ago.

I'm sorry if my post came across as critical of those who are more diligent at replacing and testing capacitors, its just frustrating trying to find consistent sources online for inexpensive parts and information about what we should or shouldn't bother replacing.

When I mentioned not replacing all capacitors on a board, I meant that most people seem to ignore all of the very small electrolytics on a board and only replace the larger ones that more commonly fail. I will always replace all caps of a certain brand on a board when I recap due to failures, but if there are caps of other (better) brands that I don't currently have replacements for, if I test the system and it works, I don't generally replace those. So, at what point is it actually important to replace a capacitor? How old? How big or small? What location?

And no, I don't have an ESR meter. At some point you have to have limits on what you can reasonably call defective and worth replacing. It depends on your level of knowledge\skill (mine is fairly low), tools available (I have soldering\desoldering stations and a basic multimeter), and the reliability of the device (in my case, most things "seem" to me to work fine unless visibly defective). I just don't personally have the skill, equipment or time to pull, test and replace every cap on every board I come in contact with that is more than 10 years old. For the most part, this has suited me just fine and I've been playing with old hardware for years (built my first K6-2 Voodoo 2 SLI Win98 system in 2007 and its still working). I'm sure things will continue to age differently as capacitors in PCs approach 30-40+ years old, but the components I have dealt with up to now have so rarely had ANY recurring problems that I haven't even seen the need to get a tester for capacitors. Also, while I agree that seemingly infrequent problems could be related to aging capacitors, its hard to use the stability of older PCs as a gauge for determining whether it should be recapped. Systems used to crash all the time, even when new 😀. Anandtech used to actually keep track of how many crashes they experienced in a certain time period on a given platform.

My IBM 5150 does have electrolytics in its power supply, and that's what I was referring to... sorry, should have clarified. The system is jam packed full of extra hardware and it "seems" to still be working fine, despite the 30 year old 63 watt unit that sat completely unused in storage for 15 years before I got it. I may recap it at some point, but I need to get a special screw driver to get into the PSU, as it uses security torx or some crazy thing like that. I did replace a bad tantalum on a NOS Everex EGA card though. 😀

Anyway... this is an interesting discussion, I hope to learn more about all this stuff eventually.

You are playing Russian Roulette with applying full rated voltage to aluminum electrolytic capacitors that have sat unused for many years without reforming them first.

Ozzuneoj wrote:

Anyway... this is an interesting discussion, I hope to learn more about all this stuff eventually.

I forgot to say, "good topic." Thanks for starting it!

I don't have any computers pre 1980's (unless you want to count a 70's era Atari 2600 as a computer). On older machines you can blow things up by running them at full power. I don't think this is the case with modern computers. I do know some CRT tv's would blow chips if their capacitors were bad (and CRT TVs tend to run hot).

You can buy a cheap ESR/parts tester on ebay (mega 328 based ones for example) for a few dollars. Granted it uses a 9V battery for voltage so accuracy of anything using higher voltage is not exact but most PC capacitors are close. Those devices come in very handy and I suggest people have one around.

Apple computers that used SMT and thru hole aluminum capacitors from the Quadra through the G5 era have issues and tend to need replaced.
Generic and OEM PCs that were made through the capacitor plague era also need capacitors replaced.

Tantalum capacitors that are run over specified voltages (from power supplies that are not running in spec) will explode and could take other components with them.

I tend to stock only a few specific capacitors I need all the time (SMT 46uf 16V for example) and order the rest as needed so they don't sit around for too long. Liquid capacitors have a shelf life and a powered on usage life (time @ specific temperature). Everything wears out eventually but the way things are engineered computers tend to work even if some parts are out of spec.

Old caps... its all down to how good the caps are to begin with. I tested a few caps in my 1978 TV a year ago an they where not all that far from speck.
Meanwhile a motherboard that 10-15 years old can have junk for caps.

as for NOS caps, unless if you working on something funky that you can't get a new cap for, just buy a new cap. Its just not worth all the trouble only to have the cap fail say a year or two latter.

I wonder, since we're talking about electrolytics.. Where can I find out date codes of these caps ?
- If I wander through my local electronics shop of choice, I'll see the same looking capacitors again and again.
How can I be sure these are still good and not something like ~15 years old already ?
- Asking the employed people in front of other customers isn't polite and seems impudent.

If this forum supported polls I'd set up a poll to see how often people have instability problems with old parts in general, or how often parts with problems have been fixed by replacing otherwise decent looking capacitors.

That's really my main reason for asking this question. I can't see why an old capacitor that was made in 2005 and never used is any worse off than one that was made in 1995, was used for years and hasn't been used since 2000, and yet the vast majority of us enthusiasts on this forum don't recap all of the boards we tinker with, nor do we have problems with them. So, at what point does it become necessary or even make a difference? Are we going to see a sudden mass extinction of all the old boards, CPUs and cards due to slowly declining flitering caps 20 years from now? Will we still care? How many times are we planning to recap our boards until we're so old that can't do it any more? 🤣

After looking a bit it does look like the prices on Mouser are a bit lower than I remember. I remember shipping costs being quite a bit higher and most parts I needed didn't give much a volume discount. I just saw some Nichicon caps with similar specs to the Sanyos I posted above for about 34 cents each for 10+ (22 cents for 100+). Still not as cheap as the random old stuff on eBay, but its more reasonable than I remember and shipping is also not bad (4.99 for cheapest usps shipping).

Well, I think the experience of failing caps isn't quite as black and white - as you basically stated as much with the question about mass extinction of all the old boards, etc due to "slowly declining filtering caps." There shouldn't really need be a point at which we as retro collectors and enthusiasts go from "everything still works OK" to FAIL-BOOM. It can happen. It does happen. Does it happen to everyone? No.

But the simple fact is that electrolytics have a lifespan. They also have a tolerance that swings around their rated values. The circuits also have a range of acceptable values. So even as the caps age and capacitance increases and ESR increases, things still work. They may continue to work fine for years and years.

Unless we are all original owners of the retro hardware we use, we are unaware of the history behind all the components we acquire. Likewise, as collectors, there are a decent number of us that are committed to preserving this hardware for the long term. I'll admit that I chuckle a bit at some of the heat paranoia when it comes to heatsinking old processors that didn't originally require cooling or stuffing a ton of heatsinks across a Voodoo card despite the fact they shipped and worked just fine without them. But then I shrug because the reasoning for this is longevity of those components. Preservation.

So I guess the true question comes down to how much one cares. And that is a truly subjective question. Is it fun in the short term to just build an old computer and game on it - don't replace the caps and when or even if it goes... it simply goes? Maybe it takes another 20 years for those electrolytics to fail. At that point, will we still care? Another perspective is replacing capacitors, VRMs, heatsinking VRMs, ICs, etc., and trying to treat your motherboard, PSU, etc. like it is staying at a resort in attempt to increase the lifespan to as long as possible.

I can't see why an old capacitor that was made in 2005 and never used is any worse off than one that was made in 1995

Someone can validate or correct me on this, but that is an interesting choice of years you used because motherboards basically went tantalum->electrolytic->polymer with electrolytics spanning a large percentage of product from 1995-2005. Shifting the focus to longevity of tantalums or polymers from electrolytics is a bit of an apples to oranges to bananas scenario.

Ozzuneoj wrote:

I have a question for everyone who tinkers with old hardware and on occasion has to replace capacitors. […]
Show full quote

I have a question for everyone who tinkers with old hardware and on occasion has to replace capacitors.

I am mainly talking about electrolytic caps.

Its a basic question. If any of us can dig a 10-30 year old computer out of a scrap heap, power it on and NOT have capacitors explode or have the system immediately become unstable, why do some people make such a big deal about buying New Old Stock capacitors? I've read about people building "capacitor reforming" stations out of breadboards and laptop power adapters to "heal" the capacitors because of film layers degrading over time etc. etc. etc....

And all that sounds perfectly reasonable, but why don't we see the effects of capacitors sitting unused for years in our various devices?

I haven't had to replace capacitors that much on older devices, but one does have to know about caps when designing electronics.
Sure, I've seen some motherboards with bulging/leaking caps, but only one of mine has exhibited this (Abit KR7A-RAID). Still haven't got around to replacing the caps though 😀
My set-top box did need new caps as it started glitching; well known issue around the net.

Anyway. If the caps are gone during storage time, they are gone, no matter if they are unused or soldered on a device.

It depends on the storage conditions (temperature, humidity). The electrolyte tends to evaporate and the rubber/plastic seal tends to break over time. Some caps are rated 1000h when stored at slightly higher than room temp (that's 42 days) and some are rated 10 years under controlled climate.

But it does not mean that the caps are completely useless after too long or improper storage, they are just out of manufacturer defined specifications that are valid for brand new tested caps. For instance the oxide layer may be degraded so that leakage current is 100 times larger than in specification until the oxide layer is reformed again. Usually manufacturer specifies that after some time (maybe year or two in storage, whether unused or mounted on device) there is a need to reform the oxide layer by applying rated voltage for some time through a resistor to limits the leakage current while electrolysis happens. And if the leads oxidise over time, so they will be difficult to solder as well, so opened package kind of should be used while it's still fresh and thus expired capacitor reels are not used in the manufacturing plants.

If however the electrolyte has evaporated too much, oxide layer degraded too much or sealing gone bad so it leaks, then the cap will be quite useless, it may be too far away from any capacitance or leakage current specs and can even be shorted so it heats up and explodes when powered.

So sure, when you take out a device that has been 10-15 years in basement and turn it on, the capacitors will have excess leakage for sure. But normal leakage is quite low, let's assume in the order of 0.01mA, so if one cap has 100-fold leakage, that's 1mA per cap, and assuming 100 capacitors (overkill?), that's still only 100mA of excess leakage current which is pretty much nothing compared to power supplies capable of several amps. It might be tough for the caps to suddenly have the voltage over them without current limiting, but if the other option would be to solder them off for proper reforming, one might as well put fresh caps there.

Just a reminder that as there are different applications for capacitors, there are different capacitors designed for these different applications.
Some capacitors are used in switch mode power supplies (like PC PSU and motherboard Vcore VRM), they have to have low ESR for handling huge ripple currents at tens if not hundreds of kHz frequency.
Some capacitors are used in linear power supplies like wall warts (at least back in the day), they don't need to have such low ESR nor huge ripple current handling ability, and they are used only at mains frequency or double of that (up to 120Hz).
Some capacitors are used in audio circuits, so there will only be like voltages not really exceeding +/- 5V AC over them. Some have also DC bias over them, not exceeding much over 6V.

All this is relevant only to electrolytic caps.
Other caps have their own peculiarities, like tantalum caps not liking large surge currents so they tend to explode.
Or ceramic caps whose capacitance drop somewhat proportionally to voltage over them.

And about that preventive maintenance by recapping everything that's old; sure changing the caps is good when there are signs of the caps going bad, but too often when something is broken there is the mentality of "it must be bad caps and all must be changed to low ESR solid polymer caps" or something similar, while it may not even be the caps at all and the real reason could be determined by small amount of logical thinking. I mean that's somewhat comparable to a car that might have one loose screw and the car will magically get better and faster by changing all screws to acid-resistant screws, even the ones that don't need to be acid-resistant but a plastic screw is good enough.