Questions About Re-Stuffing Old Caps

Discussion in '"Boat Anchor" & Classic Equipment' started by N4ZAW, Dec 7, 2017.

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  1. N4ZAW

    N4ZAW Subscriber QRZ Page

    I'm currently "re-stuffing" all the caps in a radio, and was wondering what the substance is, that they used to seal the original cap. It's not a big deal, but I always thought they used beeswax --- and this ain't beeswax by any stretch.
    It still melts nicely in the oven at 250* F for 20 minutes just like beeswax, but then, it solidifies hard and brittle, like some form of plastic.

    I was intending to refill the new caps with the same goo that I got out of them. But that's clearly not an option. Can anyone tell me what this stuff is?
    I plan on sealing with "Goop"... A well-named, clear, paste-like stuff, that cures like a rubbery, semi-solid plastic. I would also like to know any other methods that you use, that might be better.

    lcap stuffing1.jpg l cap stuffing4.jpg
  2. KB4QAA

    KB4QAA XML Subscriber QRZ Page

    I'm sure they used some additives to the beeswax base. However, I have never seen any formula nor discussion of the material. A major drawback to beeswax is that it supports fungal growth.
    N2EY likes this.
  3. KC8VWM

    KC8VWM Moderator Volunteer Moderator QRZ Page

  4. W9GB

    W9GB Ham Member QRZ Page

    You may have come across Rosin, familiar to violinists (music) and old radio/TV techs (soldering).
    Rosin is the resinous constituent of the oleo-resin exuded by various species of pine, known in commerce as crude turpentine. Rosin has been noted in some Zenith antique radios.

    You can use beeswax or candle wax for re-stuffing. Some have tried hot melt adhesives.
    Look at the ingredients, Wikipedia article lists most common formulations.
    Some Antique Radios forum members purchase bad paper capacitors for their re-stuffing.
    Here is an example from a Zenith restorer.

    Early Television Museum restores 1930s and early post-WW2 televisions,
    with the goal to to retain “original look” and construction of period.

    3. Wrap a new capacitor with paper to make the total diameter of the capacitor and paper slightly smaller than the inside of the old housing. Insert the new capacitor in the housing. If the fit is not snug, the hot wax will drip through. Note: new capacitors are much smaller than the original ones. In some cases two capacitors can be put in series or parallel to get odd values or higher voltages. Both will usually fit in the old shell.
    4. Using the heat gun, melt candle wax of the same color as the old housing. A tin can with a small spout made with pliers works great to hold the wax. Support the capacitor with one end up, then pour the wax in the end and allow it to dry. Turn the capacitor over and pour wax in the other end. Another approach is to use a hot glue gun. Colored glue sticks are available from glu-stix.

    5. Re-install the capacitor in the circuit.
    6. Often capacitors have been replaced with modern (postwar) ones. In order to make the chassis look as authentic as possible, I remove the modern capacitors. I also remove the paper label from one of the prewar capacitors in the set and scan it into my computer. I then use Photoshop to create new labels for the capacitors which had been replaced with modern ones. Using Photoshop, I change the capacity and voltage on the label to match the values I need. Old capacitor shells salvaged from immediate postwar sets are then rebuilt as described above. The labels are then glued to these capacitors.
    Last edited: Dec 8, 2017
    KE5OFJ likes this.
  5. K1ZJH

    K1ZJH Ham Member QRZ Page

    A lot of us use hot glue. It comes in colors that match the original fillers at the factory.
  6. KE4OH

    KE4OH Ham Member QRZ Page

    Hot glue.
  7. N4ZAW

    N4ZAW Subscriber QRZ Page

    Much thanks for all the info and tips... Never thought of scanning/printing replica labeling, or the use of hot glue. I can assure you both methods will be adopted here.
    And thanks for the link to the Electrical Engineer's Handbook page showing the different formulas and compositions for the "goo" they used. ;)
    And thank you for the OTHER links, too.
  8. W9GB

    W9GB Ham Member QRZ Page

    Sean -

    C.E. "Sonny" Cutter (Radiola Guy) of Portland, Oregon documented the DIY modern reproduction of the No. 6 dry cell battery using a 2.5" mailing tube, "C" cell holders, and brass 8-32 hardware. Today, he sells high quality reproduction labels (various brands) fir antique radio restorers.
    2013 QRZ Thread
    For his No. 6 Dry Cell he used TAP Plastics Epoxy Resin as a top sealant.
    A1163518-A817-4AB3-B495-33B1FE23C998.jpeg 255C7E7A-6523-473E-B589-2A893C992E89.jpeg

    High Quality Labels
    Last edited: Dec 9, 2017
    WB4TAA, W6ELH, KD2ACO and 3 others like this.

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