RoyC Posted September 11, 2005 Report Share Posted September 11, 2005 Ever wonder what is on the inside of those old waxy capacitors?Roy Link to comment Share on other sites More sharing options...
dynaco_dan Posted September 11, 2005 Report Share Posted September 11, 2005 Hi RoyCI looked at the lower photo first and then the upper photo.You did a fantastic job of putting it back together, just as it was from the factory.I felt like joking tonight, could you guess.Seriously though.Was this a defective capacitor?Thank you for showing us the inside construction of the capacitor, with all of my experiences I have never seen the inside of a capacitor before.Have a great night.>Ever wonder what is on the inside of those old waxy>capacitors?>>Roy Link to comment Share on other sites More sharing options...
RoyC Posted September 11, 2005 Author Report Share Posted September 11, 2005 This combo cap was out of spec. The 4uF section measuring nearly 6uf and the 6uf section nearly 8uf.It appears to be a roll of foil separated by a very thin membrane of paper that has an oily smell (PCB oil?!). Taps for the 3 wires are inserted at various points.I've attached two more photos of the paper and foil/paper sandwich..Roy Link to comment Share on other sites More sharing options...
dynaco_dan Posted September 12, 2005 Report Share Posted September 12, 2005 Hi RoyC againDo you or any other reader have an idea what the frequency cutoff would have been changed to if these were now +/- 50% tolerance.I can only assume that there would be a few more out in the field with the same spec's.This maybe is typical of why reviews were not always exactly the same but close enough.Thank you again RoyC for this very interesting information.Have a great evening.>This combo cap was out of spec. The 4uF section measuring>nearly 6uf and the 6uf section nearly 8uf.>>It appears to be a roll of foil separated by a very thin>membrane of paper that has an oily smell (PCB oil?!). Taps for>the 3 wires are inserted at various points.>>I've attached two more photos of the paper and foil/paper>sandwich..>>Roy Link to comment Share on other sites More sharing options...
Pete B Posted September 12, 2005 Report Share Posted September 12, 2005 Very interesting Roy, this supports my theory that those caps are not pure paper dielectric. Capacitors as I understand it are called dry as long as the oil does not slosh around inside, so these are oil caps not purely paper as some have stated. This article states that caster oil can raise the capacitance by a factor of 5 which sounds in the ball park for these caps (from http://www.vcomp.co.uk/tech_tips/reform_ca...form_caps.htm):"The capacitance of a condenser is directly proportional to the area of the electrodes spaced by the dielectric and is inversely proportional to the thickness of the latter. The nature of the dielectric is the third determining factor for the capacitance. If this dielectric medium is a mineral oil, the capacitance of the condenser may be, for instance, twice as great as it would be with air, everything else being the same. With castor oil the capacitance will be about five times as great as with air. The ratio of the capacitance of a condenser with a given dielectric medium between the electrodes to the capacitance of the same condenser with air (or, more accurately, vacuum) as a dielectric is designated the dielectric constant of the medium or its specific inductive capacitance."also interesting:"The following example may illustrate the great compactness of the low-voltage electroltyic capacitor as compared with an equivalent wax-paper capacitor. A unif of the former class designed for use in a unidirectional circuit and rated for 2,000 MF at 5 to 10 volts (depending on the ripple voltage) can be housed in a container of about 10 cubic inches, while the capacitance of the lowest voltage condenser of the latter class, occupying the same space, will be of the order of only a few MFs. Consequently, the bulk, weight and also the cost of the electroltyic capacitor are in this case less to a very great degree.The cause of this impressive difference between the two kinds of capacitors will be discussed in the following paragraphs. As already stated, for a given type of dielectric, the less its thickness the greater the capacitance per unit electrode area. The limit for increasing the capacitance by this expedient in nonelectroltyic condensers is determined by the gauage of the thinnest available insulators which will provide the required dielectric strength. For example, it is difficult to make condenser paper thinner than 0.0003", and it is the usual practice in the manufacture of wax- or oil-impregnated paper capacitors to place at least two layers of paper between the foils, to prevent breakdowns due to unavoidable pinholes and conducting particles (metallic specks, and the like) in the paper. Thus, 0.0006" between the elctrodes appears to be the minimum spacing. But even if a chance were taken with a single layer of paper between the foils of a condenser for very low voltages, the ultimate minimum spacing would be 0.0003", which would also set the limit to the capacitance per unit area for this type of dielectric, no matter how low the voltage rating of the unit. Thus, whether the latter were intended for 5 volts or 25 volts, it could not occupy a space less than that required for the housing of a section of the required capacitance wound with a 0.0003" paper betwen the foils."A few more interesting links regarding electrolytic caps: http://www.vmars.org.uk/capacitor_reforming.htm http://www.duracap.com/electrolytic_capaci...ation_guide.htm http://www.cornell-dubilier.com/Pete B.>This combo cap was out of spec. The 4uF section measuring>nearly 6uf and the 6uf section nearly 8uf.>>It appears to be a roll of foil separated by a very thin>membrane of paper that has an oily smell (PCB oil?!). Taps for>the 3 wires are inserted at various points.>>I've attached two more photos of the paper and foil/paper>sandwich..>>Roy Link to comment Share on other sites More sharing options...
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