VOGONS


Reply 20 of 36, by gdjacobs

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PC-Engineer wrote on 2020-08-01, 20:38:
In nearly all cases in Switching Power Supply Units/Circuits the function of the Electrolytic Capacitors are for filtering (mini […]
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In nearly all cases in Switching Power Supply Units/Circuits the function of the Electrolytic Capacitors are for filtering (minimalizing the AC ripples on the DC voltages). As higher the current, as lower the needed amplitude of the AC Ripple, as highe r the needed capacity. The power dissipation on the ESR correlates with the frequency and the current. The main effect of a higher ESR is a higher temperature of the capacitor. The good message is, that the modern low ESR electrolytic capacitors accept higher temperatures.

For Recaping you should follow this rules:

  • rated Voltage must be equal or higher (the higher voltage rating of the capacitor doesn’t lead to higher voltage in the circuit!)
  • rated Capacity must be equal or higher (would not take more than double)
  • Pitch of the legs must be equal
  • Diameter should be equal or larger (better heat dissipation), depends on place around
  • Hight should be equal or larger (better heat dissipation), depends on place above

As higher the capacity and/or as higher the voltage, as higher the volume/surface of the capacitor (hight and/or diamater). So for temperature critical capacitors for the CPU voltage regulators it can be smart to use capacitors with a notch higher voltage rating and so a higher hight/diameter for better heat dissipation.

You can test the thermal result in situations with high CPU load (Prime95) with your fingers on the capacitors. I use for recapping low ESR capacitors from Panasonic, Epcos and Yageo. And I never had capacitors which are not long-touchable.

The first criteria is correct.
Sufficient capacity (capacitance?) is more important on a 50/60hz line rectifier than smoothing the output of high frequency switching transistors. There you want an appropriate ESR as higher ESR directly translates into higher ripple voltage.
Matching the leg pitch is desirable but not essential. Sometimes close enough is good. Sometimes you bodge your way through (usually when you don't have SMD parts on hand).
There are rules of thumb for heat dissipation and case size, but the best solution is to use a capacitor with appropriately high ripple current rating.

All hail the Great Capacitor Brand Finder

Reply 21 of 36, by PC-Engineer

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In general you are right and you know what you are doing and you are able to read, compare and understand the data sheets.
I think the most users here (without a title from an university) would suffice from rules, which help to chose sufficient and obtainable capacitors.

The goal of all doing is to reduce the AC ripple in all situations (frequencys and fast load jumps) and to reduce the inductance near the switches (transistors, ...). The effect of the capicitance is reduced by the ESR.
As the ESR and the complete filtering behavior of the capacitor varies over the frequency, the temperature, the age and also with the brand/supplier (technology). I think there is calcultaed a lot of tolerance by the engineers of board manufacturer. The scattering over all effects leads to situations where the ESR of a special Low-ESR capacitor is lower than an other Ultra-Low-ESR capacitor. The limits of Low and Ultra-Low are not clear defined. To minimize the costs it is also common to chose only a few types for the entire board - what means that not always the calculated capacitance is used. As the ESR gets lower with higher capacitance and larger dimensions, it can also be a disadvantage to chose a lower capacitance for a better ESR rating. The topic is complex and there is no single answer or rule for chosing a replacement.

I have very good experiences with the easy obtainable (and also longer lasting) Low-ESR types from the brands i have listed regarding the rules i have listed.
Recaping is always a risk to destroy the board. So it could be a good strategy to chose longer lasting Low-ESR types instead of the Ultra-Low-ESR types (to do it once) and to reduce the load jumps and the current - means no hard overclocking

1994/1995 - Socket3 - ASUS SV2GX4 / POD 100MHz / 64MB / SCSI - Windows 95

Reply 22 of 36, by pentiumspeed

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Main issue is discussion is going wide and large and this is really grand. Yes, I studied electronics, researched capacitors and was member of a badcaps once. But this forum fell apart and full of spams. And incidentally I liked to get bulk purchases at good price of Samxon but they are no longer easy to obtain also in series I wanted.

Problem is, reality is hard and solid. The ones people suggested are more than decade old and makers of capacitors had dropped some so this leaves me with fewer options.
Knowing what to get is the main battle and this is where people talked about fell short.

The knowledge gained by substituting and get proper results is the *current* knowledge I wanted to know about so I can order fresh set of capacitors that works for these that is no longer available for example ultra low ESR is no longer easy to find. EG: Will polymer capacitors work in this regard, so on? And standard low ESR what is the current series that I can order from. I can get from ebay and mouser so need to know these.

One time I ordered capacitors from ebay seller that claimed this is correct type of capacitors that works and turned out it is not acceptable substitute for what I needed to repair the LCD TV few years ago that friend purchased used needed recapped.

Cheers,

Great Northern aka Canada.

Reply 23 of 36, by darry

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pentiumspeed wrote on 2020-08-02, 18:56:
Main issue is discussion is going wide and large and this is really grand. Yes, I studied electronics, researched capacitors […]
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Main issue is discussion is going wide and large and this is really grand. Yes, I studied electronics, researched capacitors and was member of a badcaps once. But this forum fell apart and full of spams. And incidentally I liked to get bulk purchases at good price of Samxon but they are no longer easy to obtain also in series I wanted.

Problem is, reality is hard and solid. The ones people suggested are more than decade old and makers of capacitors had dropped some so this leaves me with fewer options.
Knowing what to get is the main battle and this is where people talked about fell short.

The knowledge gained by substituting and get proper results is the *current* knowledge I wanted to know about so I can order fresh set of capacitors that works for these that is no longer available for example ultra low ESR is no longer easy to find. EG: Will polymer capacitors work in this regard, so on? And standard low ESR what is the current series that I can order from. I can get from ebay and mouser so need to know these.

One time I ordered capacitors from ebay seller that claimed this is correct type of capacitors that works and turned out it is not acceptable substitute for what I needed to repair the LCD TV few years ago that friend purchased used needed recapped.

Cheers,

IMHO, buying capacitors on Ebay is a recipe for getting either cheap crap or counterfeits .

Reply 24 of 36, by pentiumspeed

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It was identified as genuine and had photos of these and seller seemed knowledgeable, and behaved like seller was in repair business and when I received them was not good one. Then I knew why. I have seen this happen due to people not knowledgeable in other words, didn't research and did not vetted them as good subs.

Oh well, as was needed a kit. Yet there are good sellers but I had to search and verify the series that is appropriate to this applications is major task. This why I asked here what the brands and series of them that are current production and so I can just go there and search and buy them.

Still no answer here yet some of you said that worked well, please provide the brand and series of these capacitors (especially electrolytic low ESR capacitors)?

Cheers,

Great Northern aka Canada.

Reply 25 of 36, by TheMobRules

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pentiumspeed wrote on 2020-08-02, 21:25:

Still no answer here yet some of you said that worked well, please provide the brand and series of these capacitors (especially electrolytic low ESR capacitors)?

When it comes to brands it's easy: Nichicon, Rubycon, United Chemi-con (also known as Nippon Chemi-con) or Panasonic.

As for specific series, it really depends on the component you are trying to recap and its age. But as a general guideline:

  • Pre-2000 power supplies: Nichicon UPJ/UPS, Rubycon YXF, UCC LXV/LXY
  • 2000-2005 power supplies: Nichicon UPW, Rubycon YXG, UCC LXZ/KY, Panasonic FC
  • Pre-S7 MB: in most cases anyting rated 105C should work, Intel used the old equivalent to Nichicon UPM on a lot of their boards
  • Socket 7, Slot 1: Nichicon UPW or equivalent
  • S370, Socket A: Panasonic FM, Nichicon UHW, Rubycon ZLQ
  • S478/775, 754/939: these usually have ultra-low ESR caps, you'll probably need to use polymers here

Series to avoid: Nichicon HM/HN, UCC KZG/KZJ as these are almost guaranteed to fail prematurely (I don't think they are in production anymore though)

Again, it's better if you provide specific examples of what you need to replace, I'm just basing this on past experience but the options could change depending on the board. If you want to be certain it's worth to put some effort on finding the datasheets of the caps you are replacing (if possible) and browse Mouser or Digi-Key for japanese caps with similar specs.

Reply 26 of 36, by schmatzler

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pentiumspeed wrote on 2020-08-02, 18:56:

for example ultra low ESR is no longer easy to find. EG: Will polymer capacitors work in this regard, so on?

Anecdotal evidence: I've replaced all of the regular 1000uf@6.3V capacitors on my Abit VH6T with Polymer capacitors (X-Con ULR1000/6.3L). The board still works very well and stable.

I'm not a professional expert in board design so it's probably not a good idea for every project, though.

Edit: I've mostly used Panasonic EE and Nichicon UVZ series for all of the other caps. Full list is here. These are good as in "worked well for a year".

Reply 27 of 36, by gdjacobs

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Replacing HM, HN, and KZx series with poly caps is really the only option now. Panasonic FM series and low ESR caps with similar specs can also be replaced (for ex with Panasonic SEQP, SEP, or UCC PSA series when used in high frequency switching applications, like a VRM filter). This is generally an ESR upgrade, so there's a small chance of instability (depending on how sensitive the feedback circuit is).

I haven't looked in depth at matching higher ESR caps as they have high reliability replacements available, but I suspect there's nothing on the market that's appropriate.

Last edited by gdjacobs on 2020-08-03, 17:46. Edited 1 time in total.

All hail the Great Capacitor Brand Finder

Reply 28 of 36, by pentiumspeed

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My applications: is to rebuild PSUs: this will be compaq proprietary PSUs to safeguard against blowing up, and one of my generic baby AT PSU. I also ordered 2 Astec baby AT PSUs and they tend to be well built.

And as usual pentium III motherboards and socket 462 boards.

Also small capacitors (under 470uF), I intend them to be low ESR or polymers that I find in PSUs and boards. The small capacitors tend to be real troublemakers in PSU as they were used as both filtering voltage and signal coupling, the sizes are around 10, 22, 33, 47, 100 and 220uF in size, usually 50V.

For now that's all I think of that needs them.

Cheers,

Great Northern aka Canada.

Reply 29 of 36, by gdjacobs

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pentiumspeed wrote on 2020-08-03, 17:35:

My applications: is to rebuild PSUs: this will be compaq proprietary PSUs to safeguard against blowing up, and one of my generic baby AT PSU. I also ordered 2 Astec baby AT PSUs and they tend to be well built.

I wouldn't use poly caps for this, unless you're working on a more recent PSU. You'll want a good supply of Nichicon PW, Panny FC, etc. for general purpose use.

pentiumspeed wrote on 2020-08-03, 17:35:

And as usual pentium III motherboards and socket 462 boards.

Definitely, poly caps are excellent as replacements for KZG, KZJ, HM, HN, etc.

pentiumspeed wrote on 2020-08-03, 17:35:

Also small capacitors (under 470uF), I intend them to be low ESR or polymers that I find in PSUs and boards. The small capacitors tend to be real troublemakers in PSU as they were used as both filtering voltage and signal coupling, the sizes are around 10, 22, 33, 47, 100 and 220uF in size, usually 50V.

For now that's all I think of that needs them.

That should be fine. Just try to match ESR and ripple and be aware that no poly caps are bipolar.

All hail the Great Capacitor Brand Finder

Reply 30 of 36, by digger

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Aside from PSUs, when it comes to capacitor replacement, doesn't vintage hardware have much more lenient tolerances than newer motherboards that run at much higher clock speeds and at much lower voltage levels?

Reply 31 of 36, by TheMobRules

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digger wrote on 2020-08-03, 19:27:

Aside from PSUs, when it comes to capacitor replacement, doesn't vintage hardware have much more lenient tolerances than newer motherboards that run at much higher clock speeds and at much lower voltage levels?

I would assume that an old 5V CPU can tolerate significantly more ripple in absolute terms than a modern 1.4-1.5V processor. If we're talking about percentages of the nominal voltage then I'm not sure really. But in general modern PC components seem to be more sensitive than the old stuff.

Reply 32 of 36, by gdjacobs

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All else being equal, reduced ripple is always better as it translates into reduced heat stress and improved service life for semiconductors.

All hail the Great Capacitor Brand Finder

Reply 33 of 36, by Miphee

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It doesn't matter. People build and test these computers for a few days or weeks at most then get bored with them, sell them or put them in storage for a long time.
They won't be used 10 hours a day for years like modern computers. It's pointless to overthink this "issue". Use whatever reputable brand your local store sells.

Reply 34 of 36, by appiah4

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All this talk of ESR for Socket A stuff and I never had an issue with replacing failing shit Teapo caps on Socket A boards with other shit caps like Koshin; they just work fine. Has anyone done a recap tht didn't work properly due to high ESR?

Retronautics: A digital gallery of my retro computers, hardware and projects.

Reply 35 of 36, by IBMFan

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Miphee wrote on 2020-08-04, 04:34:

It doesn't matter. People build and test these computers for a few days or weeks at most then get bored with them, sell them or put them in storage for a long time.
They won't be used 10 hours a day for years like modern computers. It's pointless to overthink this "issue". Use whatever reputable brand your local store sells.

+1
I almost excusively use used caps from previously working electronics and never had an issue.I only care about capacity and voltage and the rest are irrelevant to me. It's not professional but it's very practical,I won't spend $15 to recap a $5 psu when I can do it fo free with used parts.Last time I needed 6 pcs of 560/16 low-esr caps for a board and it was a grand total of $22(12+10 shipping), that was the cheapest option.So I just replaced them with standard 560/16 used caps I already had and it was all good.It's just not worth the investment for a part that is barely used.

appiah4 wrote on 2020-08-04, 06:21:

All this talk of ESR for Socket A stuff and I never had an issue with replacing failing shit Teapo caps on Socket A boards with other shit caps like Koshin; they just work fine. Has anyone done a recap tht didn't work properly due to high ESR?

Only 1 way to find out. replace all caps on a board with standard types and run a stress test on it continuously for a few weeks.
I'm 100% sure it will work fine after that.
You know what?I mght just do it for science with one of my rigs.I'll find the shittiest brand of used caps I have and put them to the test.

Reply 36 of 36, by PC-Engineer

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Electrolytic capacitors have an behavior similar to batteries. If they getting older (by age/storage or by usage) the ESR rises and the capacitance decrease. The effects are accelerated by temperature - each 10K higher temperature doubles the aging speed.
The most old, 20years aged boards, work fine with well aged capacitors.

I had changed some bulbed capacitors, which had a capacitance within 10% tolerance to nominal value and some inconspicuous capacitors with only 30% of nominal capacitance. Was not able to measure the ESR, but would suspect, that it’s value was massively increased. Anyway, what happens by aging with the capacitors is not identical over all brands and their technologies. As observable on many consumer boards the supplier often chosed cheap, fast aging capacitors also for high class boards. So i suspect it is not important to chose the best possible ESR for the capacitor. I think recaping the consumer boards from Asus, Gigabyte, Abit, ... with low-ESR types from high-quality brands is always better than keeping the old ones. High quality brands with focus on reliability like Intel, Fujitsu-Siemens, Ibm, Compaq, ... took often high-quality caps.

Again, i recommend to take low-ESR types of high-quality brands from your local provider. And if you want to make it better, then solder a SMD ceramic capacitor (e.g. Kemet type 0805 with 220...470nF for 3mm pitch) between the legs of the electrolytic capacitor on the back of the PCB.

I recaped (appr. 5 caps) the first board (Epox S370, bought in 2000, got unstable with bulbed capacitors) in 2001 with standard low-ESR types from Panasonic, which ran until 2004 without trouble and bulbed caps.

1994/1995 - Socket3 - ASUS SV2GX4 / POD 100MHz / 64MB / SCSI - Windows 95