Reply 20 of 71, by bloodem
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- Oldbie
rasz_pl wrote on 2022-08-01, 17:43:what you need is
-low ESR
Of course, low ESR is nice to have, but "need" is a bit of an overstatement.
I have been recapping boards since 2005. In the past 5 - 10 years or so, I have been using high quality and low ESR caps (just because I can).
However, at one of my old jobs in the 2005 - 2010 period, never did we use low ESR caps (and, overall, the caps we used were of average quality... at best). We were the type of company that mostly dealt with other companies (private or public), so we always knew how our repairs fared over time (since these were our clients). And, yeah, after recapping them, some of those boards continued to run in the harshest of conditions, 24/7, without any problems. In fact, I don't remember a single instance where a motherboard that I or my colleagues recapped died at a later date.
Now, I'm not an electronics engineer, I'm a software engineer, but my experience tells me that, if the cap does not get hot during normal operation, then you don't need lower ESR.
If ESR is an issue (like is usually the case with switching power supplies), the first sign of trouble is the fact that the capacitor will get hot (and even explode in a very short amount of time if there's too much ripple current that it can't handle).
If capacitors remain nice and cool, then lower ESR (although still nice to have, especially from good brands) is far from being a requirement.
And a short (very recent) story related to this:
A few weeks ago I was in my hometown and took my mother's car for an oil change, checking the brake system, etc. She specifically told me to go to a certain small(ish) auto repair shop, because she knew the owner.
Well, while being there, I ran into one of my friends and ex-colleagues, who is one of the technical contacts for this repair shop (employed by a different company), and he was doing some maintenance work for them (fixing & cleaning the printer from the accounting department, among other things). As it turns out, after talking to him, I realized that this auto repair shop actually had one of my old motherboards (an Asus CUBX).
I had almost forgotten about this, but my friend had contacted me in 2018 (knowing that I'm into retro computing), and asking me if by any chance I had a spare motherboard with ISA slots. I told him that I did have ~10 such boards (10... at that time, since then my insanity has ownly grown 😁). He further explained that he urgently needed such a motherboard to replace a dead motherboard that belonged to an "auto repair shop" which had a very old software solution for the brake test platform. All in all, the brake test app only ran on Win95 (maybe Win98, but it had never been tested) and used a proprietary ISA board. Every hour that the brake test platform was offline resulted in a very substantial money loss for the auto repair shop. So his only requirement was: the most stable motherboard that I was willing to give up (something with 440BX preferred, obviously), and at least one ISA slot. CPU speed was not particularly important.
At that point I had just received a working Asus CUBX in decent condition, I had tested it and it was very stable (but it did have some slightly bulged caps).
Four years ago, socket 370 boards were very easy to come by (sometimes for free ar almost for free), so I easily gave this one up (I was definitely not willing to give him a Slot 1 board 😜 ). Now, because having a stable and (hopefully) long-lasting motherboard was of utmost importance, I quickly did a full recap. Of course, I wasn't very willing to use any of my Panasonics / Nichicons / Rubycons (and didn't even have that many of those, anyway), so I used some cheaper Fujicon general purpose caps, since I had many of these. Hardly a "good brand", but I had used them for 'less important' recaps before without encountering any issues. After that, I sent him the board, threw in a 1 GHz Coppermine (which is still quite cheap), a 128 MB PC100 module that I had used for testing + a new Matrox G450, just to be on the safe side.
Fast forward to 2022: as you've probably guessed by now where I was going with this, my motherboard has been running for the past four years, almost 24/7, in one of the harshest conditions possible (dusty environment, hot/cold weather, humid air, etc), and they've confirmed that so far they've had no issues with it.
Now, one might be wondering why they continued to use such an old brake testing platform (I also had the same question myself), and they told me that the platform had originally been installed in 1996, together with other technical equipment, and the investment had been substantial - over $500k (which was a lot of money for a new & small neighborhood auto repair shop). Since then, the platform had worked flawlessly, they do have a very strict maintenance schedule for it, they replace all the required consumable parts, etc. Unfortunately, even though the manufacturer still offers spare hardware parts for the brake test platform itself, they never bothered to update the software for this particular model.
So, having said that, don't be afraid to use general purpose caps on (most) motherboards (especially if it's not a motherboard that you value in particular, but you still want to see it fixed), because they are totally fine as long as you have a stable platform after that and the caps themselves don't get hot.
2 x PLCC-68 / 4 x PGA132 / 5 x Skt 3 / 1 x Skt 4 / 9 x Skt 7 / 12 x SS7 / 1 x Skt 8 / 14 x Slot 1 / 6 x Slot A
5 x Skt 370 / 8 x Skt A / 2 x Skt 478 / 2 x Skt 754 / 3 x Skt 939 / 7 x LGA775 / 1 x LGA1155
Current PC: Ryzen 7 9800X3D
Backup: Ryzen 7 5800X3D