Help Needed To Identify A Capacitors Markings

Discussion in 'The Projects Forum' started by jayjay_uk, Apr 30, 2014.

  1. jayjay_uk

    Thread Starter New Member

    Apr 30, 2014
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    First off... i am new to the forums and new to electronics in general. I have been doing a lot of reading on components and how they work and what they do... so far so good.

    I have been repairing a graphic equalizer (kenwood ge-7030) that needed 5 new electrolytic's from what i think was maybe a mains spike... two main caps on the ac line in... and every 10uF cap on the main board either had a low reading or non at all... it is working fine now.

    As a project i have been reading about changing capacitors and resistors to higher quality caps and metal film resistors of better quality to tighten the tolerances and hopefully improve sound... the equalizer did not cost me anything so its sort of a little project of tinkering so i have something to focus on while i am learning.

    I have come across what i believe to be either metalized/polyester film capacitors and cannot find the markings or a chart anywhere that describes what the markings mean... i am using an online calculator at the min just to punch in the 3 digit numerical code and see what the value is... then check it with a test meter... but i am stuck with this one as i am new and hoping some one here with more knowledge could help me out.

    I have attached a picture... while looking there is actually another ceramic disc cap i cannot identify... i know the values of the cap's but not what the other markings mean...

    the two different caps in question are the (L274) and the (SR183K)

    Any info/help would be very much appreciated... i have been searching google for a full day and cannot find anything on these caps... or if anybody knows of a link to a site where i can read up on them would be even better.

    Cheers.

    jayjay
     
  2. THE_RB

    AAC Fanatic!

    Feb 11, 2008
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    STandard small cap markings are the same as the traditional 3-band resistors;
    number, number, how many zeros

    so;
    274 = 27 and 4 zeros, = 270000 pF = 270 nF
    183 = 18 and 3 zeros = 18000 = 18 nF

    you will notice the first two number correspond to the standard number pairs used in resistors;
    10 12 15 18 22 27 33 39 47 (etc)

    There is no need to replace those caps, they are extremely unlikely to have failed in a low voltage audio device.

    And don't believe what you hear from those retards on Audiophool forums... Changing a polyester cap to a polyprop cap will NOT make your device "sound better".
    :)
     
    #12 likes this.
  3. MrChips

    Moderator

    Oct 2, 2009
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    I agree with RB. I would not go about replacing resistors and capacitors with the hope of improving sound quality. You're barking up the wrong tree.
     
  4. atferrari

    AAC Fanatic!

    Jan 6, 2004
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    The top of the cake, in a French magazine, Electronique Pratique, was reversing the connection of the AC plug in the wall!
     
  5. jayjay_uk

    Thread Starter New Member

    Apr 30, 2014
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    thanks for every ones input here... it has helped a lot as i spent to much time trying to find the markings. what was confusing me was there is little dots next to the L and the dots vary from cap to cap... should i not have to worry about these dots? if one did go however unlikely would i just have to mach size and capacitance and i should be ok? also on the disc caps is the starting letters SR which i cannot find anything about... in general if they in this device or another ever needed changing... am i right in thinking that as long i stick to the same physical size and just mach the capacitance that i should be ok? also are the brown/redish caps metalized or polyprop caps? i am new to this so just want to be clear on what they are.

    @ THE_RB & MRCHIPS ... do you think the best thing to do is just replace broken components with new alike components and just repair when needed?

    @ atferrari ... i read awhile ago about swapping the line and neutral from the ac plug but i was under the impression that was because they use to make units with the case/chassis live and to swap the line and neutral would mean it would be safer... then you can not touch the case and go to ground and get a shock... neutral would mean you would have to connect to live source to complete the circuit for a shock? just what i read and was wondering what you meant by what you said.

    thanks to everyone here who helped and gave input... also... did i create a thread in the right section about parts identification? if not can you please direct me to the right section as i think i mite need more help in the future... i always do plenty of searching first by the way... the numerical numbers i did understand it was just the dots on the caps i thought they might have represented a tolerance code or maybe a voltage code of some sort.

    Cheers

    jayjay

    EDIT:

    just so you have an idea of what i was thinking i will give the link of what i was reading about components and changing for better ones. even if changing the caps for same brand higher voltage ones and changing resistors for tighter tolerance with higher wattage if it would make the unit last longer i would be willing to do it... just for the experience and trying to get good at something if for nothing else... i will await for some more input on this before i continue as like i said... i am very new to this but learn quick. my forte is computers/software/networking/operating systems/and coding... plus electrical qualification for domestic and commercial maintenance/installations... but electronics and components seems to be the icing on the cake for me... so fascinating.

    http://www.bext.com/replace.htm

    Cheers
     
    Last edited: May 1, 2014
  6. t06afre

    AAC Fanatic!

    May 11, 2009
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    Another Audiophool idea, is to use medical grade mains sockets. Because they are sooo much better:rolleyes:
    @jayjay_uk If it ain't broke, don't fix it
     
  7. jayjay_uk

    Thread Starter New Member

    Apr 30, 2014
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    @t06afre understood loud and clear... guess i will put it back together then :)

    and as for the medical grade mains sockets... i mite just go military instead and hope that works better :) haha

    Cheers for the input
     
  8. atferrari

    AAC Fanatic!

    Jan 6, 2004
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    No, no; the author, NOT ME, was recommending to swap positions between A and B.

    Good luck in your reconditioning.
     
  9. t06afre

    AAC Fanatic!

    May 11, 2009
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    Yes do not waste time and money on changing caps(DoH). There are so much other stuff you can get to improve your sound system :phttp://www.goldensound.com/productlist/next-generation-audio-accessories
     
  10. MrChips

    Moderator

    Oct 2, 2009
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    I have actually witnessed in the past where turning around a 2-prong AC plug fixes a mains hum problem and I don't think it had anything to do with a live chassis issue.
     
  11. jayjay_uk

    Thread Starter New Member

    Apr 30, 2014
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    Thanks for every ones input here... has helped me along the way.

    @t06afre why did i not speak to you earlier? i would have just bought everything on that page before i picked up a screwdriver :)

    @MrChips i just remembered something i read awhile ago and thought i would mention it... but i will remember that one in the future... thanks.

    i have just plugged the graphic back in and tested it and there seems to be a slight problem... one of the channels is quieter than the other one... and i have swapped inputs and outputs to make sure it was a channel after the graphic had anything to do with and it is the graphic... does anyone know of common components to look at for this sort of problem? as i am new i take the route of start with one part systematically go through them and then replace if i find a bad component that is a long process but its a project and i can do that if needed... was just wondering if anybody knew a certain area i should look? maybe transistors or resistors or caps? hope someone can help point me in the right direction.

    Cheers

    jayjay
     
  12. atferrari

    AAC Fanatic!

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    So, he was right after all...! :confused:

    What could be the explnation?
     
  13. THE_RB

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    Don't worry about the dots or other marking which are likely to be manufacturer logos etc. The 3 numbers are the cap value, and the rated voltage is 60v (standard) unless for some reason they used high voltage caps which are much larger and MUCH more expensive (so they won't use them unless absolutely necessary).

    Those brown caps are just "polyester" in the catalogues I have. Just standard poly caps.

    Generally. Replace broken parts, and replace parts that get worse with age, like electro caps where the electrolyte dries out with heat. Especially electro caps near anything hot like a heatsink.

    Never replace ceramic or poly caps unless they are blown, and that usually only happens in high voltage circuits, not in preamps run from +15v/-15v rails where the ceramic and poly caps last forever.

    Re the new fault; "quieter on one channel"; first check the obvious, swap the incoming signal leads to see if it goes quieter on the OTHER channel. ;)

    After that check the next most obvious things; adjustment pots, and crackly pots and switches. Work all the pots and switches vigorously and spray some electrical cleaner in them if needed.

    Also check all your work! When you were replacing electro caps before you may have left a bad solder joint or a solder short (splat) somewhere. Go over everything with a magnifier and bright light.

    Make sure the electros are the correct way around!

    If those things don't get you a solution its time for some photos, and we can suggest a test procedure. We need to know what test equipment you have.
    :)
     
  14. Johann

    Senior Member

    Nov 27, 2006
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    Hi, I lived in Paraguay for a while. There everything runs off 2-prong sockets, no earth wire (occasionally someone might add a loose wire from metal frame of a washing machine to an earth spike).

    We bought a new fridge and there was a slight tingling sensation when the frame was touched, so one of the locals, reacting to my concern, just reversed the plug and the problem was gone!

    Needless to say, I added an earth wire later! (just in case of insulation break-down in the motor!). I guess it has to do with the physical position of the motor windings relative to the metal core and that if the winding closest to the metal core is connected to the live wire, there probably exists a capacitive coupling of some kind. Reversing the live and neutral might then change this. Only a guess!
     
  15. jayjay_uk

    Thread Starter New Member

    Apr 30, 2014
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    @ THE_RB ... thanks for the info on caps... thought i was not going to get the answer about what caps they was... i had an idea but just wanted to be sure.

    in my previous post i did say i swapped the inputs and outputs... i also used some inline connector to go straight from the source to the output and that worked... that was the first thing i did before posting... always have to determine if its your leads/audio source (mp3) before stripping down again.

    i am very limited on test equipment i have a regulated power source and use a fluke 287 multi meter... i get by and what i need to do with them so until more equipment is required i will comtinue using them... they serve me well.

    i found the problem last night at about 1:30AM ... i had it all plugged in and playing audio as i went to attach my croc clip to the ground test point to start testing certain points to see if i noticed a difference anywhere i accidentally (luckily) bent the board slightly on the corner (where i took a picture of those caps) and it the audio became level again out of both speakers... i bent it in and out a few times just to be sure... then i investigated... i could not see any bad solder joints but there obviously was one... so i un-soldered some electro caps... cleaned the solder as much as i could of the board... fluxed the cap leads then fluxed the under side of the board and soldered them back up... by 3AM it was working again :)

    thanks for your input on this though... very much appreciated.

    just a quick question... do people here recommend using flux or should i try without first? just as it makes it so much easier and nicer i also have the flux next to the solder on my bench.

    Thanks for every ones input here... has made for some good reading.

    Cheers

    jayjay
     
  16. THE_RB

    AAC Fanatic!

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    Congrats on finding the bad solder joint.

    Electros have steel leads and often have corrosion on the leads, especially these days when the leads are ROHS tin plated not properly coated with lead:tin solder like they used to be.

    It's a big problem now, you can get new electros with fine rust on the leads. Depending how they have been stored and for how long.

    I scratch the leads with some side cutters to make sure the leads are very shiny, then coat with solder first, then solder them into the PCB. I don't generally use flux as solder already has flux inside.
     
  17. MrChips

    Moderator

    Oct 2, 2009
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    As far as I know, solder for electronics usage usually comes with a rosin core, i.e. flux in the hollow center core.

    [​IMG]

    You can buy a flux pen/dispenser that is used when working with SMD components or when you just want to add an extra dab of flux.

    [​IMG]
     
    Last edited: May 2, 2014
  18. jayjay_uk

    Thread Starter New Member

    Apr 30, 2014
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    Thanks ... i use a roll of tin:lead 60/40 with rosin core... but it either has trouble attaching to the leads/board or it leaves a big blob of solder on the board... with is why i tend to push the component in and then smear the leads and board with a bit of flux first... then solder and it just takes the right amount from the iron tip and leaves the rest on the tip... if i dont use flux it tends to take everything from the iron tip. i guess i just need more practice as i am new to soldering and electronics... but every one has got to start some where :)

    @THE_RB ... i will keep that in mind when getting new components in... cheers

    @MR_CHIPS ... thats what my solder looks like... but like i said i still find it a little more difficult without using extra flux.

    Thanks for your time in replying and answering my questions everyone... very much appreciated.

    Cheers

    jayjay
     
  19. MrChips

    Moderator

    Oct 2, 2009
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    [​IMG]

    Like many skills a good soldering job takes some practice.

    Make sure your soldering iron is at the right temperature and that the tip is clean and shiny and properly "tinned", i.e. with a fresh layer of solder on the tip.

    Make sure you heat the joint to be soldered before applying the solder wire. The solder wire is applied to the joint, not the soldering tip. It helps to get the solder flowing by applying the solder wire to the tip and the joint at the same time, i.e. by applying the solder wire where the tip touches the joint.

    Use just enough solder to form a small bead that flows through the PCB hole. Don't use more than required.

    Hold the soldering tip to the joint for two more seconds. Remove the soldering tip and allow the joint to cool for 5 seconds without any physical movement to avoid creating a "cold solder joint".
     
    Last edited: May 3, 2014
  20. jayjay_uk

    Thread Starter New Member

    Apr 30, 2014
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    @MR_CHIPS ... Thanks for that... yes i have been putting the solder on the tip and letting the flux i have put on the board take the solder away from the iron. i will put that into practice a little later when i am at my bench... very helpful... thank you. i only have a 15W 240v or a 20W 12v (which i run from an old car battery charger :) ) for little components what wattage would you suggest? also what wattage for heat sinks and big caps? i have had trouble with 15W & 20W on a big cap?

    Cheers

    jayjay
     
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