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Capacitor info

Discussion in 'General Electronics Discussion' started by gransport3800, Feb 10, 2013.

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  1. gransport3800

    gransport3800

    4
    0
    Feb 10, 2013
    I have some 4' fluorescent lights in my garage that have one light that doesn't work. I've installed new light bulbs in them, but still only one bulb works. I took them apart to check the ballasts for faulty parts. Each bulb runs off its own ballast on each end of the fixture. I noticed the the capacitor had some cracking on the coating of it. After using a multimeter to test it, I determined that the capacitor was bad. I've been trying to find replacements, but I'm having a hard time. I went to my local Radio Shack and found nothing. I've looked around on the internet and found some, but I'm not quite sure what I need as far as fared requirements. On the capacitor it has numbers that read 535J 250V, it is a reddish-brown and kind of looks like a piece of taffy with 2 electrodes coming out of the bottom. It is a 120 volt fixture that uses 40 watt T12 bulbs. Where can I find what I need and what fared do I need?
     

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    Last edited: Feb 11, 2013
  2. EinarA

    EinarA

    28
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    Feb 11, 2013
    535J would normally translate to 5.3 microfarads. This seems very large compared to what I have seen elsewhere. Either my experience isn't valid here or the numbers means something else. Posting a picture of the capacitor would be a big help.
     
  3. gransport3800

    gransport3800

    4
    0
    Feb 10, 2013
    Also molded into the plastic part of the ballast there are numbers that read 600W/600V.
     
  4. EinarA

    EinarA

    28
    0
    Feb 11, 2013
    Thank you for the picture. Not sure how big it is thou. I had decided you must have a 240V lamp but appearantly not. Is this a newer ' electronic ballast', because I was thinking of an older passive ballast that uses a large inductor and a small cap (5nF) for RFI supression? It could still be 5.3 uF but it is odd that it is a film type. I am not familiar with what you have so can't offer very good advice.
     
  5. john monks

    john monks

    693
    2
    Mar 9, 2012
    5.3uf capacitors are very common in ballast. 250volt is the minimum but I looked around and saw some rated for 450volts. This should be just fine. Film capacitors are fairly precision and inexpensive so I assume that is why they are used. Ceramic capacitors change value with voltage and temperature so I believe that is why they are not used. Many ballast are simply an inductor and a capacitor in series with the tube in parallel with the capacitor. This is a resonant circuit for your line frequency. So the capacitor must be close to the right value.

    I suggest looking for a 5.3uf film capacitor with a minimum of 250 volts or simply replacing the whole ballast circuit and being done with it.
     
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