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capacitor plague finally struck home

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Reply 20 of 28, by BitWrangler

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iraito wrote on 2024-06-17, 16:59:

I still don't understand the randomness of life expectancy for caps, i have an amiga 1200 with old caps (i checked myself during repairs) 30+ old caps and they are still working, no bulging no nothing, then you check something way newer with so called high quality caps and they are plagued.

IMO there's a design factor... if you design in a lot of latitude, it can use any caps, whatever is cheapest that month, which is why PC Chips and ECS still often work with bulgy caps and anything you can scrape up to put on them works fine... others are finely tuned tight tolerance engineering with no margin for error, needing highest spec caps in perfect condition... Asus seems to be like this... if the takeoffs from the ASUS are still +/- 20%, not leaking, throw them on an ECS.

Also PSU are a factor, if your PSU is putting out spiky shit, it will hammer the motherboard caps, maximisalating the deathalisation.

Unicorn herding operations are proceeding, but all the totes of hens teeth and barrels of rocking horse poop give them plenty of hiding spots.

Reply 21 of 28, by iraito

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shamino wrote on 2024-09-05, 23:23:
The pressure buildup that causes bulging and leaking is a sign of a catastrophic failure that's more common with caps that were […]
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iraito wrote on 2024-06-17, 16:59:

I still don't understand the randomness of life expectancy for caps, i have an amiga 1200 with old caps (i checked myself during repairs) 30+ old caps and they are still working, no bulging no nothing, then you check something way newer with so called high quality caps and they are plagued.

The pressure buildup that causes bulging and leaking is a sign of a catastrophic failure that's more common with caps that were made for very low ESR. As manufacturers pushed the ESR levels lower, the chemistry on those type of caps was more prone to being unstable. PC motherboards in the late 90s-2000s created the demand for those caps. Only the best manufacturers were able to make them reliable, and even they had some issues with some of them.

Something as old as an Amiga would have had more conservative caps that tend to be more stable. They're more likely to just quietly and gradually go out of spec without obvious signs. Also, physically smaller caps aren't likely to bulge like bigger ones can.
The only way to be sure if they're still in spec would be to desolder and measure them, but if you get to that point then there's no reason not to replace them anyway.

I once recapped a Sega Genesis console and found that all the caps of one brand were way out of spec, and another brand were all still good.

BitWrangler wrote on 2024-09-06, 03:24:
iraito wrote on 2024-06-17, 16:59:

I still don't understand the randomness of life expectancy for caps, i have an amiga 1200 with old caps (i checked myself during repairs) 30+ old caps and they are still working, no bulging no nothing, then you check something way newer with so called high quality caps and they are plagued.

IMO there's a design factor... if you design in a lot of latitude, it can use any caps, whatever is cheapest that month, which is why PC Chips and ECS still often work with bulgy caps and anything you can scrape up to put on them works fine... others are finely tuned tight tolerance engineering with no margin for error, needing highest spec caps in perfect condition... Asus seems to be like this... if the takeoffs from the ASUS are still +/- 20%, not leaking, throw them on an ECS.

Also PSU are a factor, if your PSU is putting out spiky shit, it will hammer the motherboard caps, maximisalating the deathalisation.

It makes sense, factually over the years i learned that some boards simply keep on going as if they are immortal, can't complain to be honest.

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Reply 22 of 28, by akimmet

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Your Amiga also predates the capacitor plague era. Anything made before 1999 or so is far less likely to have catastrophically bad capacitors.

However there are still some examples of known bad capacitors before then. The surface mount capacitors used on PS/2 floppy and hard drives is one example. The capacitors used in Toshiba T1200 laptop battery charging circuits is another.

The oldest example I am familiar with is the motor drive capacitors in Technics direct drive turntables. After 40 years it is rare to find an example that doesn't exhibit some evidence of leakage.

Reply 23 of 28, by asdf53

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Namrok wrote on 2024-09-06, 00:27:

I tried that at first, and had it go horribly wrong on me. I just had no clue what I was doing, and alternating between the front and back of the board constantly, I got confused about which solder point on the back corresponded to the leg of the capacitor on the front. Growing increasingly confused about why it wasn't loosening, I turned the heat on my iron up and up and up until I burned the board so badly it was a lost cause.

I never did get a plunger solder sucker to work for me. The solder always cooled off too quickly to actually get sucked into the pump. I have no idea how fast you have to be with that thing, but my hands were not steady enough to do it but a single lucky time.

Braid never worked for me either the way I've seen people do in videos. Obviously I'm doing something wrong, but without someone to watch me and explain what, I'll probably never figure it out on my own.

When the desoldering pump does not work, what's likely happening is that the solder has only melted at the top or is just barely melting, and at the same time, the adjacent traces and components keep sucking away the heat, so it will solidify almost instantly once you lift the iron. The key is to not just melt it, but melt it well past its melting point, heating up the adjacent traces and components in the process. Only then you will have enough time to pull away the iron and engage the pump. It's the same principle with desoldering braid. If it doesn't work even after turning the temperature on your iron way up, the iron just isn't capable of transferring the heat quick enough. A good sign of this happening is when the braid keeps getting stuck on the board. You either need a high performance soldering iron or you need to preheat the board. Preheating with a heat gun is the easiest and cheapest option - a $10 heat gun and a $5 soldering iron from Aliexpress are enough to recap a board.

In my opinion desoldering pumps are crap, they are hard to operate, dangerous for the user and can easily damage the board. Braid can do everything that they can do, but safer and more reliably.

And I would strongly disagree with everyone who says that recapping a board is easy, it's actually very hard for a beginner and almost guaranteed to fail on the first try.

Here's a great video of some practical desoldering that shows what works and what doesn't, and how important preheating is: https://youtu.be/EoLa9ebjwGU?t=1255

Reply 24 of 28, by BitWrangler

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IMO bevel or flow tips work best with desolder pump, you melt the blob holding iron in one hand, then go to the edge of blob holding just the very end of iron still in contact, then swoop in with the pump in the other hand, slurp.. remove iron. Alternatively, with a bit of a bigger blob on there, you can pull the solder away slightly with the flat of the bevel upright and just clinging to it, and slurp. If you're trying to hold the PCB with one hand, pick up the soldering iron, melt, put the soldering iron down, pick up the pump, arm it, then slurp.... too slow, ain't gonna work. If you have a very small or tight area where you cannot hold the iron on an edge, then you need to get the maneuver down where you roll the hand with the iron back, on the heel of your hand, then roll in the other hand with the desolder pump in one motion, unless you've heated up the whole board then that's too ouchy.

You have to suck badly at sucking until you're just kinda clumsy at it, then you have to be kinda clumsy at it for a bit until you can be okayish, then you gotta be okayish for a while until you're sorta good.... gotta just keep doing it and doing it to get better.

Unicorn herding operations are proceeding, but all the totes of hens teeth and barrels of rocking horse poop give them plenty of hiding spots.

Reply 25 of 28, by DudeFace

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Repo Man11 wrote on 2024-09-06, 00:15:

A few months ago I saw where a couple of the 6.3 volt 1500 caps on my Asus P4P 800 were bulging, and I was surprised - I really didn't think that board was at risk. But they didn't cost much, and the job isn't difficult, just time consuming. But as I've mentioned before, I cheat. I heat up each leg of the cap, alternating back and forth until I pull it clear, then I reverse the procedure to install the new ones. No solder sucking, just time and care. I think I've recapped about a dozen motherboards and a few video cards this way.

thats the way i replaced my caps as well, also 6.3v either 1000 or 1500uf, 11 in total, seems these are common ones to fail, i heated each leg and rocked the cap left to right until they where out, then revesed the process to re-install the new caps, first cutting the legs to roughly the same length as the originals,i didnt have any fancy jig to hold the board so just helt it between my knees's, 🤣, i didnt bother with a solder sucker they're really only good for larger stuff, if theres was solder still in the hole i just added more solder so i didnt have to put heat into the pads/traces, its easy to over do it and have the copper lift straight off the board, especially if you're using a basic soldering iron with a fat nib like me, also you can use an achimedes spiral drill to clear any solder from the holes, its at least safer than over heating it.

Reply 26 of 28, by asdf53

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BitWrangler wrote on 2024-09-06, 21:45:

IMO bevel or flow tips work best with desolder pump, you melt the blob holding iron in one hand, then go to the edge of blob holding just the very end of iron still in contact, then swoop in with the pump in the other hand, slurp.. remove iron. Alternatively, with a bit of a bigger blob on there, you can pull the solder away slightly with the flat of the bevel upright and just clinging to it, and slurp. If you're trying to hold the PCB with one hand, pick up the soldering iron, melt, put the soldering iron down, pick up the pump, arm it, then slurp.... too slow, ain't gonna work. If you have a very small or tight area where you cannot hold the iron on an edge, then you need to get the maneuver down where you roll the hand with the iron back, on the heel of your hand, then roll in the other hand with the desolder pump in one motion, unless you've heated up the whole board then that's too ouchy.

You have to suck badly at sucking until you're just kinda clumsy at it, then you have to be kinda clumsy at it for a bit until you can be okayish, then you gotta be okayish for a while until you're sorta good.... gotta just keep doing it and doing it to get better.

Would you mind sharing your model of desoldering pump? The ones I have used so far were all crap, but admittedly, they were rather cheap ones. I might give it another try using a better one and the technique you mentioned. The main problem was that it worked for some holes, but for the more difficult ones it didn't, and in the process, it also ripped out the vias and traces. I was lucky that I only used it on a practice board, never touched it again since.

Reply 28 of 28, by BitWrangler

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asdf53 wrote on 2024-09-07, 09:05:
BitWrangler wrote on 2024-09-06, 21:45:

IMO bevel or flow tips work best with desolder pump, you melt the blob holding iron in one hand, then go to the edge of blob holding just the very end of iron still in contact, then swoop in with the pump in the other hand, slurp.. remove iron. Alternatively, with a bit of a bigger blob on there, you can pull the solder away slightly with the flat of the bevel upright and just clinging to it, and slurp. If you're trying to hold the PCB with one hand, pick up the soldering iron, melt, put the soldering iron down, pick up the pump, arm it, then slurp.... too slow, ain't gonna work. If you have a very small or tight area where you cannot hold the iron on an edge, then you need to get the maneuver down where you roll the hand with the iron back, on the heel of your hand, then roll in the other hand with the desolder pump in one motion, unless you've heated up the whole board then that's too ouchy.

You have to suck badly at sucking until you're just kinda clumsy at it, then you have to be kinda clumsy at it for a bit until you can be okayish, then you gotta be okayish for a while until you're sorta good.... gotta just keep doing it and doing it to get better.

Would you mind sharing your model of desoldering pump? The ones I have used so far were all crap, but admittedly, they were rather cheap ones. I might give it another try using a better one and the technique you mentioned. The main problem was that it worked for some holes, but for the more difficult ones it didn't, and in the process, it also ripped out the vias and traces. I was lucky that I only used it on a practice board, never touched it again since.

Just using cheap generics, the one I've used most was from Radio Shack, blue with an aluminum barrel, just got a larger one from Princess Auto (Canada's Harbor Freight) last year and used that only a couple of times. Also have a red squeezy bulb one that I sometimes use, that one is better for sucking out of larger vias for some reason.

If vias and traces are coming up, you've burned them, or they've had corrosion from underneath, CMOS battery or something.

Unicorn herding operations are proceeding, but all the totes of hens teeth and barrels of rocking horse poop give them plenty of hiding spots.