Capacitor question on an amp (AiSHi) - Page 1
Forum section: electronics / repair

author: Syze00
author_rank: Contributor
timestamp: July 26, 2022, 04:53:07 pm
content: Hello everyone.I hope I am posting this in the right location. I am by far no electrical engineer, but I know how to replace a screen on a phone, a capacitor or some other small component others might not feel comfortable doing. I have no formal knowledge though.I assume this is the main power board since the 120 comes directly into this board and there is two distinct sides with the AC side having the giant caps. On the DC side of the power there are capacitors that I can not find a reference for. The brand is AiSHi model 1036J. They are blue and look like bipolar caps but I don't know why I can't find them even on AiSHi's own site. Can someone possibly recommend a cap or tell me whats special about these? What are the characteristics I would need to find a match besides the operating temp, uF and voltage?

author: mariush
author_rank: Super Contributor
timestamp: July 26, 2022, 05:14:15 pm
content: It's a switching power supply, so you need to replace them with LOW ESR capacitors.They don't have to be same brand, same series. Can be anything with reasonably low ESR.but if you're curious, it's Aishi RR series :http://www.paullinebarger.net/DS/Aishi/Aishi%20%5Bradial%20thru-hole%5D%20RR%20series.pdf... 1036 is a datecode, probably 2010, week 36 or something like that.The capacitance and voltage rating should be printed on the OTHER side (see 2nd picture, look on the other side)I'd probably replace with Panasonic FM or FR series, or United Chemicon KZE series, or Rubycon ZLH or YXG , Nichicon PA (or UPA), HW series....You can install capacitors with slightly higher voltage rating ( ex 35v rated capacitors instead of 25v rated)OH and what you should do is remove / scrape / clean however you can all that brown/dark cream goop that's sticking to all the components. It's supposed to be cream colored (should be same color as the material between the big high voltage capacitors) soft sticky material spread over the parts to prevent them from vibrating or becoming loose when moving the circuit board through flow soldering (wave of liquid solder hitting the bottom of the board and soldering everything, the wave can lift light parts out of the holes in the pcb.When that material becomes brown like in your picture, it's bad, and it can become conductive and basically act like resistors between various points on the circuit board ... scrape it off everywhere you see it, around the capacitors on the edge, and also on the back of that small circuit board near the heatsink that goes across the middle of the pcb.scrape even the material that's cream looking, make "channels" of no material between components by scraping that material off.

author: Syze00
author_rank: Contributor
timestamp: July 26, 2022, 07:24:34 pm
content: Thank you for that advice. I didn't know hardly any of that. I'll get my brand newly bladed utility knife and start hacking the brown goop away. I suppose I could use hot glue if needed? Just your basic hot glue stick that comes in a 20 pack for crafts or is that conductive/not recommended? Is there any issue with just replacing capacitors with low ESR ones all the time outside of cost? Would there be a time when high ESR is needed?Thank you for your help. I'm really thankful you pointed out some things I would have missed. I really appreciate it!

author: Syze00
author_rank: Contributor
timestamp: July 26, 2022, 07:28:08 pm
content: Wow. You can actually see the goop changing from silly putty beige to crusty brown.

author: mariush
author_rank: Super Contributor
timestamp: July 26, 2022, 07:36:56 pm
content: Some circuits have specific requirements ... for example some linear regulators need an electrolytic capacitor on the output with an ESR between 0.1 ohm and 1 ohm in order to be stable.For other circuits it's often better to use capacitors with not so great specifications ... for example a lot of people like using Panasonic FC capacitors in audio circuits (not in switching power supply part of an audio amplifier, in the actual audio amplifier part), claiming it sounds better compared to much lower ESR capacitors. Panasonic FC is an older series of Panasonic, which at some point was considered low ESR (and still is, but not on same level with other series like FM or FR series for example)If it's a classic power supply using a big heavy transformer, well the rectified voltage comes out of a bridge rectifier and the frequency is lower, 100-120 Hz, so having very low ESR is not that important.It's good to replace capacitors with ESR as close as possible or a bit better than existing capacitors - don't overdo it, in some cases much lower ESR can also cause issues. Current ripple is also important... new capacitors should be able to handle an amount as close as possible or better than previous capacitor.But this particular case, it is a switching power supply circuit, and it's typical to use low ESR, as the switching frequencies are in the 40-200 kHz.In the case of switching power supplies, the Impedance @ 100kHz is practically the same value as ESR so you can look at that column in datasheets.

author: Coordonnée_chromatique
author_rank: Frequent Contributor
timestamp: July 26, 2022, 07:59:27 pm
content: Quote from: mariush on July 26, 2022, 07:36:56 pmSome low ESR capacitors that come with amazing specs designed for SMPS are sometimes cheaper than general purpose capacitors because they are selled in much larger volumes today.These very low ESR capacitors will generate a huge current rush at startup, especially if they are paralelized and if there is noting to limit this current (the circuit is not designed for them) the internal pressure surge will harm them in the long term.

author: Syze00
author_rank: Contributor
timestamp: July 27, 2022, 01:28:46 am
content: I'm fairly certain that this is the schematic. I'm not good at reading them yet but I know this one doesn't have the switch so I'm fairly certain of its accuracy. Also the block diagram and pictures look very close.http://www.thompdale.com/bash_amplifier/New_2-1/New_2-1_bash_amp.htm

author: Syze00
author_rank: Contributor
timestamp: July 27, 2022, 08:32:03 pm
content: Can I ask how you match ESR when its not labelled if the cap is bad? Like if there is a Visha or some other brand, usually the only thing I can see is the uF rating, the voltage and sometimes the operating temp. I do have an ESR meter like the one pictured. Not sure if its a good one or not. All I know is I couldn't afford to spend the money on the Atlus one at the time.Just looking at Mouser or Digikey makes me realize how little I know about capacitors. In my head I've always thought Nichicon and Panasonic make good ones and it goes down from there.

author: Jeff eelcr
author_rank: Frequent Contributor
timestamp: July 29, 2022, 12:19:28 am
content: Syzeoo you look at the manufacturers data sheet on the capacitorthat you need to replace.Panasonic is a good brand.JeffOh, every time I look at the title of the post I think bless you (Aishi)(Achoo)and get a laugh.

author: BrokenYugo
author_rank: Super Contributor
timestamp: July 29, 2022, 08:08:37 pm
content: If you can't get a datasheet to get rated ripple current (mind the test frequency)/ESR/tanδ value (all are related) for the original part, you just have to make an educated guess based on what you're working on and where it is in circuit. SMPS secondary side stuff that sees the high frequency ripple needs to be low ESR/high 100khz ripple current. Close enough is often good enough, though better specs are likely going to give a longer lived repair (running a cap below rated temp and ripple current dramatically increases the hour rating) and vice versa.Often you can get away with just sorting my ripple rating@100kHz after putting in the case size, lead spacing, capacity, voltage, and temperature, with the exception of places you want a kind of crappy cap with some ESR, like around a linear regulator, mains filter caps without any inrush limiting, etc.

author: Zero999
author_rank: Super Contributor
timestamp: July 29, 2022, 09:24:48 pm
content: There are no non-polarised electrolytic capacitors in that photograph. They all have a band on the package, denoting the negative.Why do you think the capacitors are bad? The messy stuff covering them is just an adhesive.

author: Jeff eelcr
author_rank: Frequent Contributor
timestamp: July 30, 2022, 12:56:57 am
content: That adhesive becomes conductive and corrosive as it turns brownnot anything you would want on a PCB.SyzeooIf you want to add glue you want some that does not outgas I useGoop (brand) from ace placed carefully.jeff

author: abdulbadii
author_rank: Frequent Contributor
timestamp: July 30, 2022, 02:37:31 am
content: Imho likening to R's 2 or 3 digit before another last one as exponent, C has same suchso 103 x 106pF = 103 uF of same/greater V spec in 5% tolerance as its suffix is J ->https://www.electronics-tutorials.ws/capacitor/cap_5.html)

author: Syze00
author_rank: Contributor
timestamp: July 31, 2022, 04:56:50 am
content: I was just going to order a set of replacement caps for the entire boards. I do have the smaller ones on hand in a kit I purchased. After a lightning storm the speakers went muffled and looking everything up and researching the issue, replacing the caps are usually the fix. I also don't have anything to do so why not?I just never saw those particular ones before. I didn't know if they were something special that I wasn't aware of and wanted to ask about those. Also the Customer service people from the company only deal with OEMs so the best I got was a "sorry but your too small" email response. I mean points for at least responding.Also, some of the caps are bulging. I will have to remove the schmoo since one of the commenters said that stuff can become conductive over time.I spent a couple hundred bucks on this Klipsch 2.1 setup for my PC and if I can fix it, I want to. I also have the tools to make it an easier job. The hardest part is probably going to be testing the caps and other components and getting that adhesive goop off.Any circuit board safe chemicals to remove that type of adhesive is welcomed! Otherwise I'm just gonna have to hobby blade it. I don't have an ultrasonic cleaner but I have enough tools to fix this or break it professionally!

author: Syze00
author_rank: Contributor
timestamp: July 31, 2022, 04:17:31 pm
content: When I was searching Mouser or Digikey, I noticed 10% tolerance and 20% tolerance. I know closer is better, but will 20% tolerance really be ok?

author: Coordonnée_chromatique
author_rank: Frequent Contributor
timestamp: July 31, 2022, 06:26:47 pm
content: Quote from: Jeff eelcr on July 29, 2022, 12:19:28 amHi, I got a silentmaxx ATX PSU from 2003 that is still operating on a computer, the capacitors are form a small "laughable" brand named "Koshin".http://www.koshin.com.hk/news/shownews.php?id=414&lang=enIs anyone knowing this brand here ?

author: jonsig
author_rank: Contributor
timestamp: July 31, 2022, 10:08:39 pm
content: Usually i just desolder one leg of the cap and test them with PEAK ESR meter to get feeling of the caps overall condition. Those dont look like they are venting. Anyways Aishi is not bad brand, think you can see them in some apple equipment today even Delta PSU´s if i remember correctly. But those YIHCON look dubious.

author: abdulbadii
author_rank: Frequent Contributor
timestamp: August 01, 2022, 02:09:09 am
content: Quote from: Syze00 on July 31, 2022, 04:17:31 pmImho so doubtful it turns to be good, try as hard as you can get the same 5% tolerance; J suffix not K M Z 10% or more

author: mariush
author_rank: Super Contributor
timestamp: August 01, 2022, 04:39:20 am
content: 20% is more or less the standard for electrolytic capacitors.It's the "normal". No need to go for 10% - the manufacturer of the power supply took that 20% into consideration when it chose the capacitors it used there.The standard values for capacitors are also chosen on purpose to account for this tolerance.For example, you have these standard values: 820uF , 1000uF, 1200uF, 1500uF820 + 20% = 985 = ~ 10001000 + 20% = 12001200 + 20% = 1450 = ~1500so 820uF that's 10% above rated value could have same value as 1000uF that's 10% below rated value.Also, this value is not really super important, these are big capacitors used to store a bunch of energy, if it's 3300uF or 3500uF, it makes very little difference.

author: Syze00
author_rank: Contributor
timestamp: August 01, 2022, 05:16:56 am
content: Luckily I purchased one of those desoldering guns thats a vacuum and a hot tip. Makes taking things off circuit boards much much easier. Just try not to ever lose the jabby bit to open her up when its blocked up! I also got a fairly large roll of solder wick that was a generic copper braid. I notice there are a few different versions of that stuff and the type of braid. I just snip a piece off, flood it with a runny resin and put the iron on it. It seems to word out well.

author: Syze00
author_rank: Contributor
timestamp: August 01, 2022, 05:33:25 am
content: Quote from: jonsig on July 31, 2022, 10:08:39 pmIs that ESR meter I got reliable/have a decent reputation for a tool so cheap? Sometimes I can't believe you can buy some of these tools so cheap. I bought that little component tester/identifyer for under $15 that runs off a 9 volt battery and its pretty amazing how much that little thing can actually do for the price. The same can be said for that little opensource soldering iron TS100. I have a hakko station but the UI is TERRIBLE! If I had to do it over again and was broke, it would be that TS100 with a laptop charger, or even that KSGER budget station.Someone needs to come out with a budget set of soldering iron tweezers that aren't clunky. I see that they have a couple of hotplates already. It would be nice in the same designers of the TS100 made soldering tweezers that accepted Hakko tips

author: jonsig
author_rank: Contributor
timestamp: August 01, 2022, 11:18:45 am
content: Back in the day i was using one of those ESR meters from Ali, it worked ok until it diedbut should be adequate for non-professional use.I´ve used Peak ESR70 for long time, it´s reliable and i use it often.Also i used Hakko Fx951 for several years, and used KSGER with ground mod. I have not tested this TS100. Because I soon found out i dont like to work with soldering equipment where you need to calibrate the soldering tip and those cheepos usually have some sort of grounding issues and in some cases plain hazardous.The smartest thing i´ve done regarding soldering stations was buying faulty metcal station with soldering wand for 70$ and bought 15x tips for 30$ with some luck. Metcals are usually easily repairable.

author: Syze00
author_rank: Contributor
timestamp: August 01, 2022, 12:51:16 pm
content: Quote from: jonsig on August 01, 2022, 11:18:45 amI've got some tools but I'm far from a professional. Maybe compared to the people I know which is not a good thing. KIDS DON'T LET ANYONE KNOW YOU HOW TO FIX STUFF until your ready to get flooded and lowballed. I've seen those KSGER's and the build quality is a turkey shoot. You don't know what the heck your going to get. China doesn't believe in grounding in any of their electronics. They can have the wire there but just don't hook it up.