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February 23, 2012 AT 4:55 pm

Old capacitor identification

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I’ve been recently poking around an old stereo receiver, and have determined that the phono preamp is completely dysfunctional. now, this is ’70s era tech, and fairly high-end for the time. I need help identifying the construction and possible replacements for the capacitors on the preamp module.


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5 Comments

  1. They look like polypropylene film and foil type. These are pretty standard fair for a lot of audio stuff, because the frequency characteristics are generally pretty good.

  2. I would replace any electrolytics and see if that fixes it. Those poly caps hold up fairly well.

    For more info on restoration, check around the radio collector web sites like:
    http://groups.yahoo.com/group/thetransoceanicfanatic/

  3. Polystyrene and foil construction capacitors.

  4. The tubular caps with the clear ends are polystyrene and foil. They are good quality and should be good as new. They are VERY heat sensitive so be careful if you solder near them. If you still want to replace them, there value in pF is printed on the part and you can use a mylar or polpropylene. If the polystyrene caps are used in a resonant circuit with an inductor with a ferrite core, the temperatur coefficiant of the cap cancels out the temperature coefficient of the ferrite core. You have to be careful replacing caps in those circuits. In your phono preamp, there will not be resonant circuits, so this will not be an issue.

  5. Yes, polystyrene. Although generally a high quality capacitor as described, I’ve replaced some in audio equipment. Shorted or mechanically intermittent.

    Came across my first ones in a Heathkit AR-15 stereo receiver nin 1966.
    It was ahead of its time with crystal IF filters, fets, ics.

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