If cost isn't a concern, modern multilayer ceramic and polymer capacitors can be used in many of these circuits without a problem.
https://68kmla.org/forums/index.php?/topic/19 … rs-mlcc-smdsmt/
Modern motherboards have long switched away from wet electrolytic to polymers.
wrote:If cost isn't a concern, modern multilayer ceramic and polymer capacitors can be used in many of these circuits without a problem.
https://68kmla.org/forums/index.php?/topic/19 … rs-mlcc-smdsmt/Modern motherboards have long switched away from wet electrolytic to polymers.
Yes, and it would be easy to recap older mobos with polymers as the uFs are relatively low compared to some of the heftier pentium 4 boards.
wrote:Some tantalum capacitors might become volatile with age but this certainly isn't guaranteed. I will take the fact that the ones […]
Some tantalum capacitors might become volatile with age but this certainly isn't guaranteed. I will take the fact that the ones in your computer still looked to be in good condition despite being several decades old as a good sign.
They definitely don't look like wet slug tantalums. All of the ones I've seen used sealed cans, like aluminium electrolytic capacitors.
Ceramic capacitors are a better choice than film capacitors for decoupling at high frequencies, i.e. the kind of frequencies you see in computers. These sort of capacitors would be my first choice for this application since they are now available in high values which are physically small and inexpensive.
You need to differentiate between power supply decoupling and signal decoupling. I wouldn't use a tantalum for signal decoupling in an analogue circuit either, but they work very well at power supply decoupling.
It's much more likely that this is a manufacturing error than a design error.
But aluminium electrolytic capacitors also have a oxide layer which can fail.
You would use a film capacitor for power supply decoupling in a digital circuit? That doesn't make sense.
I am referring to using the films as audio decoupling-- or in general areas to replace pF tantalums. Or as I already stated, VCO tuning caps. I am not sure how you are confusing the use of decoupling with power supplies and audio, it was just a quick explanation between the two.
--> and there are specialized film power supply capacitors... so I am a bit perplexed why you are making an argument on a superficial point when I provided quite a lot of information on why vintage capacitors need to be replaced.
And yes films have been around for a long time-- and as I stated secondly-- they were too expensive for most consumer products, hence cheaper and inferior counterparts like ceramics which ARE NOT GOOD for VCO stability, and cause mechanical feedback!
Despite being decades old??? I replaced *all* of the capacitors in the system regardless of type.
Ceramic capacitors act as pickups and are not suitable for synthesizers. As for motherboards, you'd have to but nuts to put them in-- as most motherboards don't use pF. It would introduce noise over time on the bus, as well.
The design was not a manufacturing error, but a schematic error. IBM placed incorrect polarity marking on the silk-screening-- and the manufacturing assembled them according to [that] silkscreen error.
Aluminum capacitors do not use a tantalum oxide layer, which is what I was getting at.
wrote:Despite being decades old??? I replaced *all* of the capacitors in the system regardless of type.
I think it's clear my point was that you probably didn't have to replace the tantalum capacitors.
Ceramic capacitors act as pickups and are not suitable for synthesizers. As for motherboards, you'd have to but nuts to put them in-- as most motherboards don't use pF. It would introduce noise over time on the bus, as well.
No, you wouldn't be nuts to use a modern ceramic capacitor to replace a tantalum capacitor. Ceramic capacitors have improved drastically in recent years and are now available in values large enough to be useful in many applications where they weren't before. We're talking microfarads here, not picofarads.
Aluminum capacitors do not use a tantalum oxide layer, which is what I was getting at.
Why were you saying you didn't want to use a capacitor with an oxide layer then? The aluminium oxide layer in aluminium electrolytic capacitors can and does fail.
wrote:I think it's clear my point was that you probably didn't have to replace the tantalum capacitors. […]
wrote:Despite being decades old??? I replaced *all* of the capacitors in the system regardless of type.
I think it's clear my point was that you probably didn't have to replace the tantalum capacitors.
Ceramic capacitors act as pickups and are not suitable for synthesizers. As for motherboards, you'd have to but nuts to put them in-- as most motherboards don't use pF. It would introduce noise over time on the bus, as well.
No, you wouldn't be nuts to use a modern ceramic capacitor to replace a tantalum capacitor. Ceramic capacitors have improved drastically in recent years and are now available in values large enough to be useful in many applications where they weren't before. We're talking microfarads here, not picofarads.
Aluminum capacitors do not use a tantalum oxide layer, which is what I was getting at.
Why were you saying you didn't want to use a capacitor with an oxide layer then? The aluminium oxide layer in aluminium electrolytic capacitors can and does fail.
They most definitely needed to be replaced. I've worked with enough vintage electronics-- both with leaking electrolytics and exploded tantalums. You do NOT leave old capacitors in old electronics. I'm sorry... this machine was also exposed to humidity and sat in presumably a garage for 20 years.
A random blog post about recapping *synthesizers* is not pertinent to this, especially when it goes on about tantalums NOT being volatile when this can EASILY be observed, or how he says you do NOT need to recap vintage electrolytics. Oh yes you do:
That's a panasonic capacitor leaking from its bungs after 36 years. It ate the traces. Required jumpers. Roland used these a lot on their synths. Modern ceramic discs being improved don't fix vintage ceramics. And they also don't change the TOLERANCE either (as that's what I was basing my 25% tolerance off of). You need film capacitors for proper VCO tuning accuracy.
Because the tantalum oxide is extremely temperamental. Aluminium capacitors behave quite differently.
Anyway, I'm not going with this discussion further. I hate repeating the same thing over-- especially when the other person has the desire to focus on superficial points and ignore the information that confronts what they're saying.
Old capacitors need to be replaced regardless of the technology. It's not a debate. If you want to make it into a debate, please visit badcaps forums or the EEVblog forums, and inform them that tantalums from the year 1987 are perfectly reliable. Oh, and electrolytics too.
wrote:A random blog post about recapping *synthesizers* is not pertinent to this, especially when it goes on about tantalums NOT being volatile when this can EASILY be observed, or how he says you do NOT need to recap vintage electrolytics. Oh yes you do:
Please point me to the exact point in that linked page where it states that old electrolytic capacitors do not need to be replaced. You won't be able to since that statement wasn't made.
Anyway, I'm not going with this discussion further. I hate repeating the same thing over-- especially when the other person has the desire to focus on superficial points and ignore the information that confronts what they're saying.
Your desire to portray my comments as irrelevant is both incorrect and insulting.
Old capacitors need to be replaced regardless of the technology. It's not a debate.
This simply isn't true.
Just dropping in my 2 cents: I wouldn't have replaced the tantalums. As long as they haven't exploded they're good to go basically. I'd consider this obvious faliure mode a clear advantage over wet electrolytics.. You WILL know when it's time to replace them 😀
wrote:Just dropping in my 2 cents: I wouldn't have replaced the tantalums. As long as they haven't exploded they're good to go basically. I'd consider this obvious faliure mode a clear advantage over wet electrolytics.. You WILL know when it's time to replace them 😀
When a tantalum shorts out or explodes, it can do serious damage to some hard-to-replace ICs; so by then it can be 'too late' as it were. I'm not too worried about surface mount tantalums-- haven't had any problems with those yet, it's just the vintage dippers that blow up left right and centre.
All of the old capacitors in the PSU needed to be replaced as well. So there really was no way avoiding redoing the passives on something that old. One advantage is that these passives are better built as well. I did a few enhancements to various things as a bonus.
When the time comes to replace the capacitors I put in that system again, it'll be around 2034 / 2044. So it's not necessary to risk watching passives blow up.
And to repeat myself yet again for the other bloke who couldn't see the quote I already referred to.. here it is for the other readers to observe so I don't look like I'm crazy:
Second, solid tantalums can't leak because they contain no electrolyte. "So what", you might say. In a synthesizer, does it matter if the capacitors are a few grams lighter? Probably not. No electrolyte is an advantage, but many synths are loaded with electrolytic caps and they seldom leak, and even if they do, it's usually not that big a deal.
We can tell he's referring to vintage electrolytics because the whole blog is about vintage synths & recapping. And as I just showed, it is absolutely wrong to leave them in as they will leak and damage traces. I got more photos as well, but it's not necessary to keep beating around the bush.
wrote:And to repeat myself yet again for the other bloke who couldn't see the quote I already referred to.. here it is for the other readers to observe so I don't look like I'm crazy:
Second, solid tantalums can't leak because they contain no electrolyte. "So what", you might say. In a synthesizer, does it matter if the capacitors are a few grams lighter? Probably not. No electrolyte is an advantage, but many synths are loaded with electrolytic caps and they seldom leak, and even if they do, it's usually not that big a deal.
We can tell he's referring to vintage electrolytics because the whole blog is about vintage synths & recapping. And as I just showed, it is absolutely wrong to leave them in as they will leak and damage traces. I got more photos as well, but it's not necessary to keep beating around the bush.
You think the quote you bolded means that the author is saying that you do not need to recap vintage electrolytics? Is English your second language?
BTW, I actually agree with you about the need to replace a leaking capacitor. Trace damage isn't guaranteed but it's certainly possible. Pretty much everything else you've said is wrong though.
**Moderators please remove this entire thread**
Thank you
I'd prefer it if this thread is not deleted as it may help to counteract some of the widespread myths about tantalum capacitors.
Well, I'm sorry that the original post with all the info/pics of what still is a nice looking PC has been deleted.
All the electronics talk is well above my head but who cares? Its the OP's computer and he can do what he wants to it, necessary or not
Damn, wanted to see pics and the thread got neckbearded by a dielectric snark. I don't see any ripple waveforms, frequency responses, or epsilons posted neither.
wrote:Well, I'm sorry that the original post with all the info/pics of what still is a nice looking PC has been deleted.
Me too. I wish raymangold hadn't done that.
All the electronics talk is well above my head but who cares? Its the OP's computer and he can do what he wants to it, necessary or not
Agreed. I just didn't want people to be misled into thinking they needed to replace tantalum capacitors before they fail. They can last many decades and even when they do fail they rarely do so by exploding unless badly abused in some way.
Yeah this is a necropost. I was looking on info about recapping my 8580 power supply and read a bunch of garbage from someone who thinks (or thought) capacitors last forever or that it is a waste of time to replace them before they explode.
For anyone in the future who comes across this thread recapping vintage electronics is a GREAT idea. I have a pile of things sitting on my bench I have gotten cheap or free because of exploded capacitors.
Guess I'll just pull mine out and research the replacements myself. Too bad the OP got frustrated and deleted his info.
SIMPLETHINGS: Fun stuff from the 80's and 90's!
https://www.youtube.com/channel/UCLxoVzIzuIN1tQ7DRO7gB6g
