How can I improve this 5V 2A power adapter? Increase reliability - Page 1
Forum section: electronics / general

author: daisizhou
author_rank: Super Contributor
timestamp: October 13, 2025, 11:07:37 am
content: Hallo everyoneI checked a 5V 2A power adapter and found that the 400V 10uf aluminum electrolytic capacitor was damaged.I replaced it with a 450v 10uf electrolytic capacitor, and I used heat-resistant tape to isolate the high heat conduction. Can this operation extend the life of the electrolytic capacitor?I plan to use this power adapter to power the fiber optic transceiver, which is powered on 24 hours a day.I want to minimize the possibility of it failing. Are there any other improvements or enhancements that need to be made?Because if the power supply of the fiber optic transceiver is interrupted, the network will be directly interrupted. I don’t want this to happen.

author: wraper
author_rank: Unknown
timestamp: October 13, 2025, 11:20:33 am
content: How about do nothing? It's a decent quality PSU, nothing wrong with its design. Why in hell did you replace polymer capacitor with electrolytic? It's a downgrade, not improvement.Quote, to say the least.

author: daisizhou
author_rank: Super Contributor
timestamp: October 13, 2025, 11:50:19 am
content: Quote from: wraper on October 13, 2025, 11:20:33 amThe polymer capacitor has a withstand voltage of only 6V, so I replaced it with a 10V 1000uf aluminum electrolytic capacitor.

author: wraper
author_rank: Unknown
timestamp: October 13, 2025, 12:26:11 pm
content: Quote from: daisizhou on October 13, 2025, 11:50:19 amSo what? Also it's not withstand voltage, it's rated voltage, and it's 6.3V, not 6. Withstand voltage is higher. Do you think it's the only spec that's important? It had much lower ESR and like 3-6 times the ripple current rating of what you used as replacement. People use polymers as an upgrade for electrolytic to improve longetivity, yet you do an exactly opposite. You already screwed up those buck converters as in another thread. What is the supposed mechanism that Kapton tape is supposed to improve anything? If anything, you only exposed those components to additional stress while soldering them for no good reason.

author: mtwieg
author_rank: Frequent Contributor
timestamp: October 13, 2025, 12:36:52 pm
content: Agree that replacing the output capacitor is probably a bad idea. Even if you increased the voltage rating and capacitance, the ESR is probably much higher than the original cap. Was there any evidence of damage on that capacitor?The kapton tape does nothing for you. A screen door on a submarine, as they say.It's possible the input caps failed due to surges on the mains. Plugging the supply into a surge protector is probably worth a try.

author: daisizhou
author_rank: Super Contributor
timestamp: October 13, 2025, 12:40:06 pm
content: Quote from: wraper on October 13, 2025, 12:26:11 pmPolymer capacitors usually have very low withstand voltage values, so I used a new 10v 1000uf electrolytic capacitor.I usually don't consider ESR. Are you saying that polymer capacitors are better than aluminum electrolytic capacitors?Nowadays, many aluminum electrolytic capacitors look similar in appearance to polymer capacitors, making it difficult to purchase real polymer capacitors. Therefore, I replaced them with aluminum electrolytic capacitors because I have many brand new aluminum electrolytic capacitors in my electronic warehouseI want to lower the operating temperature of electrolytic capacitors by sticking heat-resistant and heat-insulating stickers. Many people say that lowering the temperature can extend the service life, so I made this improvement

author: daisizhou
author_rank: Super Contributor
timestamp: October 13, 2025, 12:45:31 pm
content: Quote from: mtwieg on October 13, 2025, 12:36:52 pmThe initial polymer output capacitor looks undamaged, but I believe it only has a 6.3V withstand voltage value, while the power output is 5V. I haven't used LCR to measure the capacitance and ESR values of the polymer capacitor yet because I think it has been used for a long time and there is a high possibility of aging, so I replaced it

author: wraper
author_rank: Unknown
timestamp: October 13, 2025, 12:49:49 pm
content: Quote from: daisizhou on October 13, 2025, 12:40:06 pmSo?QuoteIt's way more important spec than rated voltage as long as part is used within its limits. And max ripple current is even more important spec.QuoteDo you live in a cave or something?

author: mikeselectricstuff
author_rank: Super Contributor
timestamp: October 13, 2025, 01:05:44 pm
content: Replace it with a 5V 4A PSU - under-running PSUs to keep them cool is the best way to improve reliability

author: NiHaoMike
author_rank: Super Contributor
timestamp: October 15, 2025, 03:08:16 am
content: It looks like the primary caps failed from a combination of heat and the input voltage possibly being near the upper limit.

author: daisizhou
author_rank: Super Contributor
timestamp: October 15, 2025, 03:44:27 am
content: Quote from: NiHaoMike on October 15, 2025, 03:08:16 amThe original capacitors were 400v6.8uf and 400v10uf. I replaced them with 450v10uf capacitors. I don't know how long they can last.

author: kite31
author_rank: Regular Contributor
timestamp: October 15, 2025, 04:05:13 am
content: Quote from: daisizhou on October 13, 2025, 12:40:06 pmYou mean you have arranged that some radiant heat does not reach the capacitors, so where is that heat now going? How sure are you that messing with the internal thermal design is a great idea?What current does your transceiver draw? It seems likely either that you are chasing a non-problem or else add a small fan or simply uprate the power supply so it runs cooler, as already suggested.

author: daisizhou
author_rank: Super Contributor
timestamp: October 15, 2025, 04:55:38 am
content: Quote from: kite31 on October 15, 2025, 04:05:13 amThis is the first time I have done this operation, and I am not sure whether this operation will really improve the durability of the capacitor.This is my first attempt, and I have never seen others do such a modification, so I did it with a try mentality.The actual current consumed by the transceiver is about 250ma.This power supply is too small to add a fan inside. If a hole is opened, it can indeed improve the heat dissipation, but at the same time it is completely non-waterproof, so it is difficult for me to adopt such a solution.The power supply shell is marked with 5V 2A, but as you know, this type of power supply is very common in China. Who knows if it can really reach 2A or if it is a trick? There is no model mark on the main control chip.

author: wraper
author_rank: Unknown
timestamp: October 15, 2025, 05:32:46 am
content: I see no indication it could not handle 2A.

author: kite31
author_rank: Regular Contributor
timestamp: October 15, 2025, 06:18:24 am
content: If demand is only 250mA on a 2A supply (even if it cannot meet that), I think we can all go to sleep now.My fan suggestion was external, not internal, but on that current draw it is superfluous.

author: daisizhou
author_rank: Super Contributor
timestamp: October 15, 2025, 06:45:12 am
content: Please see, there is no model number marked on this main control chip, so I cannot be sure if it can really achieve a load current of 2A, and it may only reach a maximum of 1 or 1.5A

author: 5U4GB
author_rank: Super Contributor
timestamp: October 15, 2025, 06:52:01 am
content: Quote from: mtwieg on October 13, 2025, 12:36:52 pmIt depends on what you need it for. If the goal is to prevent fish from entering the submarine as it slowly floods then it's doing its job admirably.

author: kite31
author_rank: Regular Contributor
timestamp: October 15, 2025, 08:24:30 am
content: Measure the voltage under load if you are seriously worried that the advertised 5V@2A will be undershot by at least 75% (and it would still work then if it sustains something like 5V). Reading the chip alone would not tell you.

author: Psi
author_rank: Super Contributor
timestamp: October 15, 2025, 09:42:30 am
content: I sometimes do cap replacements on working things to improve reliability.It's normally just because I want to know the cap is a known genuine brand and I have doubts about it. (Usually Aliexpress things that i want to run 24/7).I also make sure it's using a cap with a nice high operating temp. Since heat is usually what kills them.Obviously you have to match up ESR/voltage/capacitance.The last thing I recall doing this to is the 5V aliexpress metal frame powersupply in the wall box that powers the Raspberry pi4 running Home Assistant

author: makebit
author_rank: Unknown
timestamp: October 15, 2025, 10:34:29 am
content: You dont have any room in that case for any fan or extra heatsinking.So do you have a thermal camera you can have a quick check to see what the temps are like while its out of the case and on 250ma load?Not a great thermal test but better than nothing.If all ok, then you also have no room to increase the mains transient transient withstand either.So a jack way to do this is to connect some bigger offline power supply to the same mains lead nearby...you will then find that the bigger input cap bank of that PSU actuallywill quench mains transients to a certain degree. Hopefully it may also have a MOV inside it which will quench any transients.Of course, try and pick one without an inrush-relay/resistor because you really just want the cap bank to be right there and available to quench any mains transients.Of course it may have a bigger mov than your little PSU, which will be handy.Or buy a littelfuse TMOV module and put that on the mains.

author: daisizhou
author_rank: Super Contributor
timestamp: October 15, 2025, 01:47:40 pm
content: Quote from: Psi on October 15, 2025, 09:42:30 amIn my country, it is difficult to buy genuine capacitors. It is not because of the high price that you can buy genuine ones.They never say they are fake, so almost every company will advertise themselves as authentic, but who knows if they are genuine?Withstanding 105 degrees Celsius has become a standard feature of almost every aluminum electrolytic capacitor.How do we usually know the high temperature resistance of a capacitor? Is it just by looking at the markings on the casing?I also know about Japanese "rubycon" and "Nippon Chemi-Con", but it is very easy to buy fakes when buying them specifically. As the saying goes, you spend more money and buy a real fake.

author: ejeffrey
author_rank: Super Contributor
timestamp: October 15, 2025, 02:30:04 pm
content: QuoteSo aside from the questionable replacements you made, I think this is the wrong idea. Modifying a mass produced commodity product like a power supply rarely makes it more reliable. Occasionally there is a product that is overall well built but has a specific known flaw. But generally products as a whole are built to a price point and replacing one or two components doesn't change that. On the other hand, any modifications adds risk. Reworked solder joints are never as good as the original. Heat from resoldering can damage other components. Assembly and disassembly can cause stress cracks.Generally the best bet is to buy a reasonable quality product and understress it. A 2 amp power supply running with a 150 milliamp load is well under it's rating.

author: tunk
author_rank: Super Contributor
timestamp: October 15, 2025, 04:27:12 pm
content: No expert, but I think one of the heat sources isthe diode on the secondary side. Your replacementis larger than the original and closer to the diode,so it should be heated up more. And I assume youused a low ESR type capacitor?

author: mariush
author_rank: Super Contributor
timestamp: October 15, 2025, 04:43:28 pm
content: A solid (polymer) capacitor on the output will be more reliable than a regular electrolytic.It can be 6.3v rated - the power supply is supposed to output 5v give or take maybe 100mV so a 6.3v rating is perfectly fine.A potential improvement would be replacing the diode with another one in TO-220 (or similar) package, which will allow you to add a "heatsink" - it cold be a plain rectangle made out of copper or aluminum sheet/foil that you could place along the corner of the board (up to the Y class capacitor (don't go over the hot/cold separation line)May also want to consider removing the NTC (the black disc component near the mains input) and replacing it with a plain wire. It's there just to slow how fast the primary capacitors charge, to reduce the inrush current. Once the capacitors are charged, that NTC is still in circuit still has some resistance so it will only make heat.Note that without the NTC, the fuse may pop when you plug the charger in the mains due to the inrush current, but you can solve that with a time delay / slow blow fuse instead of a regular fuse. (yours is already a time delay fuse rated for 2A)