I have an issue on a non-Philco radio which I expect to run into on a whole set of Philcos and others.
I have an 8mf screw mounted steel can filter capacitor. Putting new caps underneath is an issue because of space.
What I’ve seen is someone cutting the cap with a tube cutter, restuffing the cap, and closing off the cap top with a panel plug. You end up with a shorter but functional cap that fits per original installation.
Can anyone describe what I’ll find inside the cap? Is it reasonable to think I could be able to do this or is there some issue with these caps that would be a problem? I figure I’ll ask before I take the trouble to cut this apart.
There are various ways to handle this, one is to cut near just above that rolled in area is near the bottom, using the rolled in area as a glue joint, this will make the can 1/4'' shorter but nobody will notice. The other method would be to cut the cap off the top, save the cap, and glue a cork to the bottom of it making it into a sort of stopper. Is there a cap on this can or is it all one piece? If it's one piece then it's probably a dry electrolytic inside, basically a "jelly roll" of paper and foil, wet electrolytics have a cap with a vent in it, the can is aluminum in this case, older ones were copper or brass.
Another method, that I have used to repair a crudely cut can, was to put tape around the circumference of the can, and cut or file down to it, on each half, and then use some pipe, or tubing to couple the can together on the inside, though some use aluminum tape, like is used for HVAC work. I would guess that you would want to save the label, so you can cut the can either above, or bellow the label, or better yet soak it in lacquer thinner to get the glue to dissolve, and let go, so you can avoid damaging it, either replacing it or scanning and making a reproduction.
Another way is to bore out the can from the bottom, this is easier said then done unless you have a lathe. Also with a lather you can cut the rolled over edge off the bottom, hopefully releasing the insulated threaded plug, but you can also uncrimp it with a flat blade, or just file it off, then you can extract the innards of the can, restuff, and glue the plug back in, with suitable holes added for the capacitor leads to come out from.
Regards
Arran
Thanks. I think I try to cut this as suggested. I don’t have a lathe, but I do have a tap and die set. I am going to see if I can use that to simply thread the two parts of the can together once it’s restuffed. That seems a neat solution. If that works I can use that on several other similar cans.
This specific cap you have is the easiset type to restuff.
I usually cut it at the upper border of the depression (groove) such that the narrow part remains with the sawn off bottom.
I did use pipe cutter, but this is not the best as it will mush the cylinder a bit, especially at the end of the cut: this is the tool to cut thick copper, not thin aluminum. Again, it will cut, but much more accurate cut could be obtained using regular hacksaw.
I have several threads where I showed the way I did it.
This is one of them, though the caps are with caps on top, not the one you have; still the stuffing is similar.
This is a similar to yours type, though 2-section one.
The latter one shows the same body type, with the depression.
There are two ways of handling it for me,
1. As shown in the latter link pictures, I use a piece of plastic pipe, and epoxy the two parts together onto that pipe. You have to make sure your new cap fits in it.
2. I take a pair of dykes, and neatly bite into the remnants of that depression and push/twist the leaflets (formed by biting) inside a bit, so they would fit inside the remaining piece of the old cap; then smear some epoxy at the inner surface of that remaining piece and push the lower part into it, straighten it out and leave to cure the epoxy. Oh, and I put a fishpaper cylinder inside to insilate that new cap from the old case.
The depression will become a narrow groove but will still look fine, and in many cases will be consealed by that cardboard sleeve, that the cap fits into, anyway.
People who do not drink, do not smoke, do not eat red meat will one day feel really stupid lying there and dying from nothing.
Did as suggested. Cut can with hacksaw, removed internals, attached new 8mf cap - with ample use of cardboard and electrical tape for insulation.
I did have to drill about 1/2 inch for positive lead into stud from inside because solder just refused to stick despite best efforts. I also drilled a small hole for the negative lead in the can to assure good mechanical connection. Put can back together with hvac tape. Since this is an aluminum can soldering won’t work but hopefully the strong mechanical connection is enoughtl
It tested at 8mf and infinite resistance between can and positive lead so it appears to have worked.
(This post was last modified: 2 hours ago by bridkarl.)
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