Opinions/Advice on Do/Should I replace ALL Electrolytic Capacitors on old equipment?

[RetroComputingGrotto]

I've just been repairing some (very) old speakers with a loud hum that occurred as soon as you powered them on regardless if any actual audio is played through them. I work in a School so it's 99% likey that the Teachers have hardly ever turned the power off on them for well over 10+ years.



As you can see the top large capacitor on the right has a bulge on the top so defincately needs replacing. As the one next to it is exactly the same capacity and voltage I planned to replace them both.


What is your advice/opinion on whether or not on old(er) equipment that has been well used, should all the other electrolytic capacitors also be replaced as they cost just a few pennies each or am I just wasting my time and should I just replace the one(s) that are clearly faulty?

[dmill89]

I've just been repairing some (very) old speakers with a loud hum that occurred as soon as you powered them on regardless if any actual audio is played through them. I work in a School so it's 99% likey that the Teachers have hardly ever turned the power off on them for well over 10+ years.



As you can see the top large capacitor on the right has a bulge on the top so defincately needs replacing. As the one next to it is exactly the same capacity and voltage I planned to replace them both.


What is your advice/opinion on whether or not on old(er) equipment that has been well used, should all the other electrolytic capacitors also be replaced as they cost just a few pennies each or am I just wasting my time and should I just replace the one(s) that are clearly faulty?

I would say it depends. Factors such as the ease of replacing all the caps (is it only a few, or does the device have dozens/hundreds of caps, are they accessible or do you need to remove other components, do you have the caps on hand or do you need to buy them?), the quality of the caps (are they reputable Japanese/European/American brands, are they known failure-prone brands, or are they "no name" caps that are hard to find any info on?), and how critical the device is/whether you're willing to replace them all for "piece of mind" are all factors worth considering.

I do usually at least replace all the caps that are identical to the failed one(s) though.

A while back I recapped the entire secondary side of the power supply in one of my laser printers (Brother HL5250DN circa 2005), after the standby rail cap failed (with the classic "wouldn't start after a power failure" symptom), though all the caps (all Japanese) except for the standby one (which was powered 24/7 for 16 years) tested in spec, so it probably wasn't necessary, but I had the caps on hand and once the PSU was out (removing the PSU from the printer was more difficult than actually replacing the caps) replacing them was fairly easy.

I've also got audio equipment (audio applications are generally much less stressful on caps than SMPS/computer application) going back to the 1960s/1970s with caps that still test in spec, so while all electrolytic caps may fail "eventually", "eventually" may be a very long time for quality caps that aren't heavily stressed.

[Perry Babin]

It's refreshing to hear the voice of sanity when it comes to capacitors. The 'it depends' is perfect. I constantly deal with people who are going to replace every capacitor because people on the internet told them it's the right thing to do. And of course, after replacing the perfectly good capacitors with new capacitors, the improvement is night and day. The one I like the best is that it 'opens up the soundstage'. Another thing they love to do is to resolder every solder joint which typically leads to a bridge that they can't find in an amp with no available schematic diagram.

[PeteS in CA]

I can't make out the brand of the two large caps, which probably should be replaced, since one is bulged. The small ones are Illinois Capacitor, which is a fairly good brand. Replace or leave alone depends on lots of factors. Age is one. At 30YO or greater, I'd consider it. The ambient temp when in use is a factor (e.g. 85C caps in a 70C internal ambient are probably not going to last as long as if the internal ambient is 50C). The application matters. Use as a switching P/S output cap is more stressful than use as a decoupling capacitor in an analog or digital circuit. Not being powered on for a decade is not healthy, as the aluminum oxide dielectric can thin during non use (i.e. cannot withstand the full rated voltage).

[redwire]

It's a complicated decision whether or not to "shotgun it" (replace all electrolytic capacitors) in a piece of gear.
You have to consider: the age of the gear, quality of the caps, their stress level (SMPS vs audio) and how much time in your life do you want to spend fixing it.
There are times I replace all, other times only a few.

"KONMO" are known low-quality Chinese electrolytic capacitors. Notice the Illinois Capacitor "IC" logo bastardization lol. It says they founded in 2016 and are making appliances.
The prego main filter caps could have been overvoltaged or just low quality. I'd replace all, use film caps for the 0.22uF parts and let it run for decades.

The power amp IC was replaced I can see, the heatsink bar massively over-torqued bending it.

[momaka]

I agree with everything dmill89 and redwire mentioned above. Indeed there are always many considerations to take when it comes to the question should every cap be replaced or just a few?

When it comes to cheap-o computer speakers, the answer I usually give is: replace everything if the caps are "no-name" garbage brands. Reason I give that suggestion is because most cheap PC speakers I've dealt with pretty much always used garbage no-name caps, and more than 50% of the time, just about every cap inside, big or small, tested bad or about to fail. The most recent case of this was a set of Boss 3000 PC speakers - every single damn cap tested bad... except for the large filter for whatever odd reason. That one tested in spec for capacitance and ESR, though I didn't test it for leakage current, so who knows. IIRC, it was a 25V cap and had 24.5V DC supplied to it at no load. How it survived for so long is really a miracle.

On that note, check the output AC voltage of the transformer (assuming it uses a linear / AC line transformer?) and see how high it goes with no load. Then multiply by 1.4142 (the square root of 2) to get the peak DC voltage that could get to the filter cap(s). In general, it's not a good idea to run caps close to their rated voltage. Rule of thumb is to have the cap voltage rating at least 2x the circuit voltage. Of course, with higher voltage circuits, the 2x rule becomes cost-prohibitive. In those cases, 10-30% margin is not uncommon.

Given the above picture, it looks like there aren't that many caps to replace on the board (assuming that's the entire board for the speakers), so should be pretty trivial to replace all of the caps. Anything electrolytic under 1 uF you can replace with film caps.

The power amp IC was replaced I can see, the heatsink bar massively over-torqued bending it.

LOL, good catch.

That'd be something my dad would do. He always jokes the proper way to torque stuff is to go all the way until the screw/bolt head snaps, then turn a quarter turn back.
(What's worse, he's done that more than a few times by mistake, so joke's on him.)

[RetroComputingGrotto]

The power amp IC was replaced I can see, the heatsink bar massively over-torqued bending it.

That'd be something my dad would do. He always jokes the proper way to torque stuff is to go all the way until the screw/bolt head snaps, then turn a quarter turn back.
(What's worse, he's done that more than a few times by mistake, so joke's on him.)

Nope! This was done by the manufacturer as we have a fair few of these dotted around the place and the ones I've peered inside so far are all the same! 😲


They clearly didnt think about (or care about) them being repaired as the 'removable' plugs were not in sockets and were actually soldered directly on to the PCB so (as you can see on the above photo) I had to desolder them to be able to work on the PCB and remove/replace the caps!


They have pretty much been left turn on all day (and night) for the last 10 years, only exception is during a power cut in a thunderstorm!! Teachers don't know how to operate power buttons/knobs on any device from a TV to a laptop and (in this case) a set of wall mounted speakers so everything is pretty much power on all the time 😒 we did go around powering them all off during half-term breaks once but we were then inundated with helpdesk incidents saying data projectors, speakers, TV screens and computers in computer suites were all not working!! How they manage to turn on their TV and/or laptop at home is beyond me as they cant do it at School.


I replaced all of the caps, mainly to practice my desoldering and soldering technique and the speakers are now as good as new (with no loud humm/buzzing) so the Teaching and Learning can commence again when the pupils return in a weeks time 😎

[ChaosLegionnaire]

They have pretty much been left turn on all day (and night) for the last 10 years, only exception is during a power cut in a thunderstorm!! Teachers don't know how to operate power buttons/knobs on any device from a TV to a laptop and (in this case) a set of wall mounted speakers so everything is pretty much power on all the time 😒 we did go around powering them all off during half-term breaks once but we were then inundated with helpdesk incidents saying data projectors, speakers, TV screens and computers in computer suites were all not working!! How they manage to turn on their TV and/or laptop at home is beyond me as they cant do it at School.

whether this is good or not is pretty much a touchy subject because making the equipment last longer by turning them off to reduce heat dmg when not in use is a valid point. however, keeping the caps energised so they dont turn bad from being unused is also another valid point, esp. if junk caps are being used in the equipment. so i say just turn them off when not in use anyway. if it fails, it actually exposes all the junk caps in the equipment so they can be identified and replaced.

and to avoid all those pebkac issues, just turn all the equipment back on one day before school restarts or on the day itself first thing in the morning when u reach the school. if u can remember to turn them all off when the school term ends, surely u can remember to also turn them back on when school restarts?!

I replaced all of the caps, mainly to practice my desoldering and soldering technique and the speakers are now as good as new (with no loud humm/buzzing) so the Teaching and Learning can commence again when the pupils return in a weeks time 😎

whether to do a full recap or not depends on whether that fixes the problem or not. if a partial recap, partially fixes the humming noise problem and its no longer as noisy as before, then u're on the right track.

[momaka]

They have pretty much been left turn on all day (and night) for the last 10 years, only exception is during a power cut in a thunderstorm!! Teachers don't know how to operate power buttons/knobs on any device from a TV to a laptop and (in this case) a set of wall mounted speakers so everything is pretty much power on all the time 😒 we did go around powering them all off during half-term breaks once but we were then inundated with helpdesk incidents saying data projectors, speakers, TV screens and computers in computer suites were all not working!! How they manage to turn on their TV and/or laptop at home is beyond me as they cant do it at School.

I think it's more of a "negligence" problem - i.e. no one thinks or cares to "care for" stuff that is not theirs, so stuff gets left turned On all the time. This then makes everyone used to the fact that everything is always On and working without thinking about it. And when it's not working, they forget to check the simple stuff - i.e. is it plugged in, turned On, and etc. Most people also hold onto the idea that they should only do what they are paid to do at work and nothing more. So if something is not working and it's not their responsibility, they don't go out of their way (and usually at all) to see what the problem is. Just call the respective department / person responsible for dealing with that problem and call it done.

I replaced all of the caps, mainly to practice my desoldering and soldering technique and the speakers are now as good as new (with no loud humm/buzzing) so the Teaching and Learning can commence again when the pupils return in a weeks time 😎

Nice, great to hear you got them saved! - one less piece of electronic equipment for the e-Waste dump/pile.

whether this is good or not is pretty much a touchy subject because making the equipment last longer by turning them off to reduce heat dmg when not in use is a valid point. however, keeping the caps energised so they dont turn bad from being unused is also another valid point, esp. if junk caps are being used in the equipment.

Well, in the case of cheap PC speakers, it doesn't actually usually matter too much anyways, since many of these typically use a small (and inefficient) line-connected AC transformer that wastes pretty much about the same amount of power with the speakers in "off" state as it does when when the speakers are On. If the transformer is inside the speakers, this will always keep the caps "nice and warm" . And if not, then I suppose it's only down to how hot the amp IC runs while idling. Most dissipate around 1 Watt or less, so their heatsinks tend to be lukewarm usually (i.e. they're not making other things too hot.)

and to avoid all those pebkac issues, just turn all the equipment back on one day before school restarts or on the day itself first thing in the morning when u reach the school. if u can remember to turn them all off when the school term ends, surely u can remember to also turn them back on when school restarts?!

That's something I always did as a student in school, thinking I'm helping the environment. Truth is, my effort was probably a teeny tiny drop in the ocean, if even that, as most public schools waste a lot of energy and have no incentive to save anything, since it's all budgeted in and funded by taxpayers anyways. (Not that I shall argue that private schools are any better either.)