Capacitors

October 21, 2009 by
Filed under: Choosing the correct parts, Repair How-to's 

Most monitor or motherboard problems are caused by poor ventilation of the case. When the heat builds up over time it will cause parts called capacitors to blow out. Sometimes they fail quickly which shows up as a black display, no power at all or even just a flashing power light or flashing display screen. Other times they will slowly fail which is indicated by the monitor taking a long time to display a picture or a wavy picture until the unit heats up.

So what are capacitors? You can almost think of capacitors as very small storage cells, when you apply power they build up a charge and if the incoming voltage drops they will discharge and release the charge they are holding. This charge discharge allows the capacitors to help filter the power output from the power supply. The amount of charge they can hold and the discharge time are 2 things that determine the capacitor rating, these are measured in microfarads (uf). You can see in the diagram here that the capacitors are nothing more than 2 layers of aluminum foil and a paper insulator inserted into a metal can and soaked with a chemical called electrolyte. When the chemical overheats in the monitor it expands and causes the capacitor case to bulge and the aluminum layers to short out. Another way they can fail is if the top or bottom vent out and the chemical dries up. When this happens the capacitors fails to operate but looks fine visually.

What to look for on the power supply/inverter board: As discussed above the capacitors can fail in several different ways but usually will like something like these pictures.

Notice the bulging tops and even corrosion on some of them.

When repairing LCD monitors or other electronic assemblies is a very important to use the right parts or you will have to do the repair again soon or even worse it may damages the unit even more. Because of the high frequencies created in switching mode power supplies like found in LCD monitors and motherboards you need to use replacement capacitors that can take it without shorting out. You will also need to use Low ESR (equivalent series resistance) and also high temperature caps, the temperature marking will be 105c. The general purpose capacitors like you would find at Radio Shack will not work for LCD monitor repair. We recommend using Nichicon or United Chemicon capacitors, found in all of our repair kits.

When choosing replacement parts there are several things to check to get the correct part:

#1) Capacitance rating, measured in Micro Farads (220uf, 470uf, 820uf etc)
#2) Voltage rating (10v, 16v, 25v, etc) ( You can go higher on the voltage rating as long as it physically fits )
#3) Physical dimensions, measured in mm
#4) Needs to be LOW ESR ( Very Important ! !  )
#5) High ripple current
#6) High temp – 105c

Here are the capacitor series from several manufacturers you can use that have the correct ESR ratings:

Nichicon :
PM ,PW ,HE , HD , HV , HM ,HN , HZ
http://www.nichicon.co.jp

United Chemicon :LXZ ,KY , KZE , KZH , KZJ
http://www.chemi-con.com/

Rubycon : YXG , YXH , ZT , ZL ,ZLH ,ZLG ,MCZ

http://www.rubycon.com/

Panasonic :FC ,FM


Other important things to keep in mind when replacing capacitors is the polarity stripe on the side of the capacitor. When you insert the new part be careful and insert the new one with the stripe going the same direction as the old one came out. The stripe will be on the negative (-) terminal. Most boards will also have the negative side shaded and the positive (+) side marked with a + sign. If you put them in wrong they will blow out as soon as you apply power and could damage the circuit.

Be sure to look through our repair guide section, we may have a step by step guide for you model already posted. http://www.ccl-la.com/blog/index.php/category/monitor-repair/

If you need help repairing your unit you can ask questions and post pictures of the boards from your monitor or motherboard in our forums section here:

http://www.ccl-la.com/forum/index.php

Our techs will be better able to assist you with the repair by looking at the pictures of the boards.

If you do not want to do the repair yourself we do offer a repair service. You can set up a service request by filling our the request form: http://www.ccl-la.com/blog/index.php/service-request-form/

We can repair most brands of LCD monitors and motherboards.


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Comments

10 Comments on Capacitors

  1. JimUSA on Thu, 4th Mar 2010 8:01 am
  2. Great thanks for the info.

    I’ve been getting these LCD monitors for free from salvage.
    A small percent of them work, but been meaning to fix the bad ones.
    I used to be an audio tech many years ago, thought I had to brush up on my troubleshooting.
    The other option was to buy new inverter boards at around $30 to $100,
    but hell don’t even even too.
    Looks like the most common problem from reading your site and from others that it usually just caps.

    Now I can fix these great monitors and give them to friends and family et al.

    FYI for people looking for good sources for caps I spent a fair amount of time looking.
    Here is good if you can find one of his kits that fit your monitor.

    I thought eBay would be good but for the most part unless you find someone dumping them, and since it’s often hard to tell if “LOW ESR” or not, and didn’t want to buy directly from China.
    AFAIK your better of with a kit here or mouser.

    In general the higher the voltage the more expensive the cap will be.
    Like the ~100uf 450v cap (around $3.50).

  3. James Brown on Tue, 28th Sep 2010 9:14 pm
  4. When I go to my components supplier web site and narrow the choices by voltage, micro-farads anc size, I still have too many choices, even within the series that you listed. There are serveral things that would help in narrowing the choices down.

    How do I know what constitutes “High Ripple ” -What is High enough when the capacitors have several choices that seem to be close to each other..
    Also i see that capacitors have an impedance rating that varies all over the place,
    Is that important?
    Thanks

  5. CCL_TECH on Mon, 18th Oct 2010 2:44 pm
  6. Any of the ones in the correct series are good to use. The series listed are all low ESR and from left to right ranked by ripple current. The only other think to watch for is physical size, be sure to get the right diameter to fit in the same location as the old one comes out from.

    [...] You will need to use low ESR and high temp capacitors for the repair or they will fail again in a month or two. This page gives more details about the parts, why they fail and which ones to use for the repair. http://www.ccl-la.com/blog/index.php/capacitors/ [...]

    [...] You can check out this page on our web site that gives additional information about capacitors: http://www.ccl-la.com/blog/index.php/capacitors/ We have a kit with the correct parts already selected available in our web store for $16.95 with [...]

    [...] You can check out this page on our web site that gives additional information about capacitors: http://www.ccl-la.com/blog/index.php/capacitors/ We have a kit with the correct parts already selected available in our web store for $14 with free [...]

    [...] Here is the power supply board with the bad capacitors circled. You will need to replace all of the capacitors on the board not just the ones showing failure. Be sure to use the proper rated parts on the repair or you will have a failure again that could cause additional damage to the monitor. Here is a page that describes what capacitors are and which ones to get for the repair, Capacitor page. [...]

    [...] Be sure to use good quality low ESR, high ripple current, high temp capacitors or you can damage the power supply board. More information on getting the correct capacitors can be found on our capacitor page. [...]

  7. rowland on Mon, 7th May 2012 8:44 am
  8. Afternoon, i’ve been looking into buying the capacitors i need, unfortunately, the Nichon’s page is not very helpful (especially for a noob like me); united chemicon’s page is good but I still don’t know how to order. And Rubycon is for experts.
    And I need them shipped to Spain.
    Could someone please assist me with this?
    If it would be possible, I would buy the repair pack, without the soldering iron, screwdrivers, etc (only the capacitors)
    Previously I wrote on the forum http://goo.gl/oc5EN .
    Thank you in advance.

  9. Larry Gallegos on Fri, 4th Jan 2013 7:15 pm
  10. Hi, guys,
    I have a four-year old HP f2105 monitor that I like very much, but that has developed the apparently common problem of capacitor failure on the inverter board. The picture comes and goes in about a four second pattern and eventually fails completely so that the power switch becomes ineffective. I have a little training and experience replacing modular parts, but little experience with precise soldering. Can I perform this capacitor replacement or would it be worth shipping to you guys for repair? The replacement of the board would cost about $100- in parts or about $160- to have a shop do the job. Refurbished monitors are available for about $180- ( they, of course, have a warranty ).

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