Re-stuffing a filter capacitor

Discussion in 'General Electronics Chat' started by Gdrumm, Aug 26, 2014.

  1. Gdrumm

    Thread Starter Distinguished Member

    Aug 29, 2008
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    Re; Old tube radio repair.
    I bought some parts, and replaced all the caps, but the guy I ordered from sent me 2 elecrolytics that I didn't recall ordering.

    Turns out, they were for re-stuffing the filter capacitor.

    I took pictures, and made a sketch, but have yet to understand exactly how to combine the two into one.

    I think the two negatives go together and go to ground, and the 2 positives go to the other original red wire coming into the bottom of the can.

    I've Googled and Youtubed, but I still don't get it; how to replace the old Filter Cap with these two electolytics.

    Does anyone have any advice, or a really good link for a first timer, that will explain what replaces what, and where?

    Thanks,
    Gary
     
  2. MaxHeadRoom

    Expert

    Jul 18, 2013
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    By filter capacitor, do you mean the main DC smoothing caps? Or filtering what?
    If so, and the voltage is right, IMO you should assume they are both fitted in parallel across the DC.
    What value are they?
    Max.
     
  3. Gdrumm

    Thread Starter Distinguished Member

    Aug 29, 2008
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    Max,
    I think the original was 40uf at 250v, and 30uf at 250v.
    I'll double check when I get home.

    I'm not sure of the exact name, it's a small aluminum can (a little larger than a roll of Quarters),. It was surrounded by a cardboard sleeve, with the readings staggered one on top of the other. The one I saw on Youtube was simply referred to as a Filter Capacitor.

    In removing it, I destroyed the can, but salvaged the base of it, and the cardboard sleeve. I'm not interested is astetics, so I just need a little help to wire up the replacements (the two electrolytics).

    I can post some pictures of the original and the replacements, in a couple of hours.

    Thanks
     
  4. MaxHeadRoom

    Expert

    Jul 18, 2013
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    Can you also define the section that the cap is connected to?
    Sounds like a main DC filter caps?
    Max.
     
  5. alfacliff

    Well-Known Member

    Dec 13, 2013
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    restuffing means to reuse the case of the cap to make it look origional. the origional had several sections, sometimes marked with holes in the connection tabs on the base as to which value goes to which tab. the negative leads all go to the tabs on the case. I usually just leave the origionals in and cut off the connections on the bottom, since they are probably dried out and bad anyway, and put in a couple of terminal strips to hold the new caps. that way, the radio looks the same from the top and nobody can see the bottom anyway.
     
  6. Gdrumm

    Thread Starter Distinguished Member

    Aug 29, 2008
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    Here are a few pictures.
    I have a rough drawing as well, but will need to make it into a .bmp

    Thanks for checking this out.
    Gary
     
  7. MaxHeadRoom

    Expert

    Jul 18, 2013
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    it Looks like what appears to be dual section cap replaced by two individual versions.
    If so you just connect them up in parallel in place of the original two, if the resistor was between the two positive ends of each, then it was set up as a simple R/C Pi filter, which you can replace as original.
    Max.
     
  8. Gdrumm

    Thread Starter Distinguished Member

    Aug 29, 2008
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    Okay,
    Thanks for the feedback.
    I'll revisit my drawing to insure it's wired correctly.

    I'll post back if I need help.

    Gary
     
  9. alfacliff

    Well-Known Member

    Dec 13, 2013
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    there is a lot of info on rebuilding old radio on the web, google "boatanchors" another name for heavy old radios.
     
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  10. Gdrumm

    Thread Starter Distinguished Member

    Aug 29, 2008
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    Here is my attempt at drawing what it looked like from underneath.

    I could still use some guidance on how to hook up the electrolytics.

    If not here, I'll join a Radio forum.

    Thanks for looking.
     
  11. MaxHeadRoom

    Expert

    Jul 18, 2013
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    You are sure the original in the can is a single cap as you seem to indicate
    From the photo is looks like a dual cap, also in your drawing what numbers are the two that you want to hook up?
    I only see low value caps in the sketch?
    Max.
     
  12. Gdrumm

    Thread Starter Distinguished Member

    Aug 29, 2008
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    Max,
    Thanks,
    The cardboard sleeve that surrounded the can says:
    MFD 40 DCWV 150, and
    MFD 30 DCWV 150

    The 2 capacitors sent to me are:
    47uF 160v(PX), and
    33uF 160v ((YK).

    So from what I saw on Youtube, I need to connect these together.
    I'm just unsure how to go about it.
    I think I saw the guy joining the 2 neg. wires together, and then connecting them to ground, and from there on I'm lost.
    What to do with the other two wires from the capacitors.

    I may have to buy a schematic.

    Gary
     
    Last edited: Aug 27, 2014
  13. MaxHeadRoom

    Expert

    Jul 18, 2013
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    If these two capacitors are to replace the double can then the -end of each goes to chassis, and the 47uF 160v replaces the 40uF and the 33uF replaces the 30uF.
    The carbon resistor goes between the +ve end of each cap, although it appears to be a fairly high value than normal, what does it measure?
    There would also be another conductor connected to each +ve connections of the original caps.
    Max.
     
  14. GopherT

    AAC Fanatic!

    Nov 23, 2012
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    Boat Anchor refers to the fact that it is heavy and useless (to most people) for anything other than a boat anchor.

    Unfortunately, some of us are compelled to delay the date that they end up in the landfill or recycling center.
     
  15. Gdrumm

    Thread Starter Distinguished Member

    Aug 29, 2008
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    Good information and thanks for the feedback.

    Maybe I'll have time to work on it this weekend.

    I appreciate you guys.

    Gary
     
  16. BR-549

    Well-Known Member

    Sep 22, 2013
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    Alfacliff is right. The thing you need to watch is that on those old tube circuits, one of the electrolytics might be reversed for a negative supply for grid bias. Double check polarities on old cap. If in doubt, acquire print and check.
     
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