you are clicking on the wrong videos then... this guy definitely does it the hard way

Thanks for the essay Regards

All of that, plus he was replacing elyts in a switch-mode PSU secondary side and DID NOT mention ESR. I couldn't believe my eyes. Picking the right capacitor for the job is *crucial* and it's not just a matter of capacity and voltage. Thumbs up for Nichicon, but he skipped the choice of product line. After that, I'm not at all surprised that he has not mentioned solid polymer - which in my experience turns the circuit immortal (as far as capacitors go), except in rare cases the tiny ESR may destabilize the feedback loop of the SMPS, and solid poly also should *not* be used in filters or RC timing circuits, due to their inherently higher leakage (would skew the timing or ruin operation of the circuit). Regarding ESR (and permitted ripple current, which is the flip side of the same coin), you really need to study a handful of vendor datasheets to get a clue. You will likely end up settling on one or two high-grade families of wet aluminum elyt capacitors from each top-notch vendor (Nippon Chemicon, Panasonic, Nichicon, Elna, Kemet, maybe one or two others) and you will specifically know that there are the cheaper product lines, from those same vendors, that you need to *avoid* for SMPS use. Any solid polymer (almost regardless of vendor) beats any aluminum elyt, except that solid poly is not available for higher voltages and it features that slightly higher leakage which matters in analog circuitry = for those two cases you go for quality wet aluminum. The caps originally used likely have twice the nominal voltage (or more) compared to what they actually sustain in the schematic. This is for practical reasons (BOM variety reduction) and there was a rule of thumb that "nominal = twice the actual voltage" results in maximum lifetime, all else equal. And then the board maker would typically save on cap vendor and ripple current dimensioning. So if I have a chance (I have a schematic or I can measure the circuit beforehand), and I have a clue about the function of the circuit that I'm recapping (most often some stabilized PSU rail) I first look for a solid poly that's just "one step up" from the actual voltage (such as: 5V actual -> 6.3V nominal) as for solid polymer this is perfectly okay. And on SMPS secondaries, I go for a cap model that fits in the space (diameter and height), that's available to me (stock levels are problematic nowadays), that has appropriate nominal voltage, and I try to max out the capacity. Even in the polymer range, I tend to find a cap that has larger capacity (and I could actually go even with a lower capacity, as it's really ESR that matters in SMPS secondaries). And I can be pretty sure that any polymer will have significantly lower ESR than the comparable aluminum wet elyt I am replacing = ESR is not much of a concern in that case. Concerns about "higher capacity than original = risk of blowing an inrush-limit NTC" is only any concern in the SMPS PSU *primary* side, where you likely won't have enough space to hitch capacity up anyway. This concern could also be valid for audio amp rail voltage, on a secondary side after a conventional 50Hz iron-core transformer (which can carry several times its nominal power, for a limited time during inrush). In contrast, in SMPS secondaries, don't worry about inrush. Inrush does certainly happen on startup, but is inherently soft-limited by the SMPS main stage maximum carried power, and the energy storage capacity (in watt-seconds) is far lower in the secondary, compared to what's stored in your primary, because of E=(1/2)CU^2, and because of the capacitances typically present in the primary and secondary side. Also, the secondaries only start charging after the primary inrush is safely over, and the main stage starts up. If you'd crank up the secondary side capacitance *way up high* (decimal orders), the SMPS would probably detect a failure to reach output rail voltage within some timeout and would either shut down altogether (output short circuit detection) or would keep re-trying (hiccup mode), and might as well reach normal operation after a few hiccups (or not). Some industrial PSU's are actually protected by a constant current limit on the output (time-unlimited, or time-limited for e.g. 3 seconds) but that's not something you'll find in PC's / displays / consumer electronics. BTW, thumbs up for mentioning IPA for cleaning, and the various flux varieties. I have one specific use for aggressive acidic flux in microelectronics: it's an excellent agent for de-oxidizing your soldering tips, including the hollow variety in desoldering guns. An oxidized tip ruins your whole soldering experience. I keep around a few coin-sized scraps of sheet copper or tin-covered iron, and a small flask of "stainless steel flux". When my soldering tip goes dull, I depose a tiny drop of that acidic flux on a piece of tin-covered metal sheet, and wallow the tip around for a bit in the molten tin+flux. The fumes are really bad, but the tip is like new. Then there are some "best practices" for taking care of your tips, such as apply a droplet of tin on the tip when turning the iron off = keep it soaked. And, bronze or brass shavings are more appropriate (sensitive on the tip) than a wet sponge. And a tip for working with the heated desoldering hollow tip/gun: apply the tip on the component leg being desoldered, wait for the tin to melt through the hole, and then gently wiggle the hollow tip around on the leg, by circular motion, and only then apply suction, while still wiggling around. In problematic holes (large areas of spilled copper) the air sucked through the hole will quickly cool down the hole below the melting point, but chances are that this motion helps you clean the hole thoroughly before that happens. When I have a problem with "too much copper around", there are pre-heat aids (pads) commercially available, or I apply additional heat on a nearby soldering pad, or I can apply a thin local streak of hot air... sometimes I would use four or five hands, rather than just three 🙂 Actually as a first measure, if I fail to desolder a lead-less leg upon the first attempt, I apply a drop of Sn60Bb40 on the leg, which hopefully soaks through the hole all the way to the component side, and dilutes the pure tin - so that the second attempt has a better chance of succeeding. A colleague used to have a special tin wire with Bismuth content, for this very purpose (low melting point, diluting problematic solder joints when desoldering).

And sometimes pcb boards made mistakes with printing and when the board was made, caps blew of course the polarity was wrongly printed on the board, to cut costs the guys who solder the boards ignored the wrong print and installed it right. Now years later you come along and follow the printed negative sign. Bang caps blows up. You allways check if the print is 100% correct on the installed cap. If not always follow installed caps negatives. Make pictures first!!!!

Yeah, in my 58 years of soldering I've heard all that before, but consider it overly cautious. Kind of like how you should never leave your house without a broad-brimmed hat because of the risk of skin cancer. Well, maybe, but probably not. I do have an assortment of solder suckers and solder wick of varying sizes, but in my experience you can do more harm than good if you try to get too fancy. The technique I've illustrated doesn't require expert soldering skills. Competent, yes. Expert, no. I prefer to keep it simple and avoid overthinking it. And let's not forget that for many people the alternative would be to junk the whole device, so what's there to lose?

dangoodell2 fair enough, each to his own I suppose 🙂

@@dangoodell2 I totally agree with you!

​@@dangoodell2 I've reached the same conclusions as you after 6 years of working on vintage audio gear. Solder wick and desoldering tools work well.... but they require more application of heat to the board. It's a compromise- less old solder in the joint, yet more heat applied to the contact and surrounding components. Fine and dandy if it's a modern board with sturdy contacts/traces/layer construction, not so good when you're dealing with the flimsy old yellow boards of the 70s-80s. Personally, I'd rather reflow the leftover solder with fresh Kester rosin flux and Kester 63/37 than risk lifting a contact or trace. Not to mention the time savings- when you've got 24+ channels to recap on a mixer, getting every last bit of solder off the joint would triple the repair time. I see full desoldering as "high risk" with minimal gain. The less heat into the board, the better.

​@@dangoodell2 let's thank the good comment before being defensive only.

Hi washu. Big fan here! S2

@@KaiSoDaM Why that you for your kind words, but I'm not entirely sure, what are you referring to.

no... it's not, poor method

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theres always one.

As a general rule, I do not try to remove old solder unless I can't get a good joint with the new component. You can make a mess if solder drips across circuit board traces where it's not supposed to, especially if the traces are close together. However, in some environmental conditions really old solder may oxidize enough to develop a gray, gritty coating that comes off on your fingers. Such solder probably won't bond with the new part and can leave you with a cold solder joint. In that case, remove the bulk of the old solder and apply new solder. You don't need to get all of it off, just enough so the rosin in the new solder can finish the job cleaning the contacts for a good, new bond. You can use solder wick or a solder sucker. I've also had success just lifting the board an inch or two off the workbench and letting it drop. If you use this latter technique, add a bit of new solder to the old solder so the ball of solder will be a bit heavier, then drop the board so the molten solder drops onto the workbench in a small ball. With a little forethought you can orient the board so to lessen the number of components the ball will drop past, minimizing the risk of the solder catching on other components and bridging circuit traces. But the need to remove old solder should be rare. Most of the time I've been able to get a good solder joint without resorting to special efforts to remove old solder. Sometimes I may even add just a touch of new solder to bolster the joint, since some of the old solder may have been taken away on the leads of the old component or on the tip of the iron. Plus, the rosin in the new solder also helps to clean the joint a tad more.

@@dangoodell2 Thanks a lot! It's good to be able to learn from the experts.

@@dangoodell2 Really excellent and detailed explanation here. Ditto for the video. Thank you.

In this context, V and VDC mean the same thing. Yours should be safe to use. Most electronic equipment operates on DC, so a power supply (either in an outboard power "brick" or built into the device itself) converts AC current from the wall outlet to DC current used internally by the device. These electrolytic capacitors are used to filter and smooth out the converted voltage. Remember that they are polarized, so make sure you orient them in the proper direction.

So how did that go? I have an old Rotel amp that needs recapping