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need help - Old cap can ID

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  • need help - Old cap can ID

    I have some old cap cans that I need to replace. I have looked on this forum and the web but I can't seem to find a definitive answer, so I am wondering if anyone here knows about this type. I know the values but I am not sure how to identify the connection posts. All appear to be single caps, not multiple caps in the same can. Having said that, all have four connection points. One in the center and three at the perimeter. The perimeter pins are used for mounting and I am assuming the extras as extra solder points. However nothing is marked. The wiring layout is confusing enough that I would like to hear some opinions before I start disconnecting stuff. Is there a wiring scheme for these as far as +/- ? Are the three outer pins identical or is one the contact point and the rest superfluous? How can one tell? Is the center pin the + or the - connection?

    here's a photo.

    If you look close you can see the electrolyte oozing out.
    Attached Files

  • #2
    i've seen similar caps (in older ampegs) and the outer posts were almost always grounded. sometimes they were attached to the metal housing of the cap.
    did you check for conductivity to ground at each terminal? that's one way to start. but i'm sure someone who knows these caps better than me will pop up here in a minute....good luck

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    • #3
      That is probably the old twist-lock style cap. The outer can also forms the four exterior tabs, which stick through slots in the chassis. This let the user mount them with no hardware, just stick the tabs through and twist the tab.

      This works great for caps with grounded (-) leads, but really badly for caps with the (-) lead not grounded. Hence there are phenolic brown boards with the right slots in them attached to the chassis so the caps can be floated.

      To answer your question, the outer can was the (-) terminal on every twist lock cap I've ever seen. It's only my native caution stopping me from saying that there never was one different. But I'd be greatly surprised.

      Your picture shows one of the lifted-negative style on a phenolic insulator board, I think.
      Amazing!! Who would ever have guessed that someone who villified the evil rich people would begin happily accepting their millions in speaking fees!

      Oh, wait! That sounds familiar, somehow.

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      • #4
        Thanks for the info.

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