Restuffing twist-lug electrolytic

[ronbryan]

I need to re-stuff a capacitor like the one illustrated. Because it is a twist-lug type, mounted in a restricted space, it has to be re-fitted using the twist-lugs, rather than a clamp covering a circular cut on the body. This precludes cutting the bottom off and prising out the bung.


Can anyone suggest a way to somehow cut around the rubber bung, without destroying it, so that it can removed and then be glued back and re-used for the terminations? I don't have access to a lathe, only hand tools.


Ron

[60 oldjohn]

Hi Ron, if you can accurately drill a central hole how about one of these https://www.ebay.co.uk/itm/Bosch-Hol...frcectupt=true
The old bung would not be a good fit, but does it really need a bung? once in place the lugs will hold can in place and no one can se the hole for the PCB. Unless it is for a metal chassis then you would have to cut and shape a piece of Paxolin or something similar and glue it in. You may find a cheaper cutter if you search.

John.

[Refugee]

If you can drill two 10mm holes side by side in the bung and then into the remains of the old capacitor this method might work.
I find it best to leave the old capacitor in the chassis.
I find removing the remains of the old capacitor a bit of a vanity thing. The only problem with this is that the old material can move about inside the can as you drill the second hole. Shoving a dummy in the first hole solves this problem.
A little spot of epoxy stops them falling out again.

[Argus25]

I have re-stuffed many electrolytics over the years, usually with the help of the lathe and other tools, machining new bases etc. However, in the case of twist lug type, I have never done it. The reason is that practically every variation of the twist lug types are re-manufactured now and available as new parts. They are available from AES (antique electronic supply in the USA who have good mail order).

The other way you could do it would be to drill a ring of 3 to 4mm dia holes close together through the soft base and near the edge, but not to damage the steel ring that is the twist lug part. Then with small sharp cutters cut between the holes remove the soft base, tidy up the cut edges and hollow out the capacitor. Then replace the base with a disc of new insulating material.

[Boater Sam]

I drill out the whole contents, wire up the new caps with insulation on the leads.
Mechanically fix solder tags onto the out leads level with the bottom of the can, colour coded.
Then fill the can with resin or silicone to the top.

[snowman_al]

If you must keep the tags and you can loose 5mm of height:

Very carefully saw through the can 5 mm above the pressed ring.
Pull the contents out and clean the can and base.
True up the bottom of the can and chamfer the internal edge.
Cut 6 slots (3 cross cuts) down the remaining 5mm 'ridge' and press them inwards very slightly.
Push the can over the ridge till it meets the pressed ring and you are happy with the 'fit'. Take it off.
Stuff the base as you wish.
Super glue or epoxy the can back on top.

Alan

[Station X]

What I do is cut the can as suggested above using a pipe cutter. Then I insert a piece of plastic pipe into the base and push the top of the can onto it. The joint can be covered with aluminium tape. To get a piece of pipe the right diameter, remove a longitudinal slice from a larger diameter pipe.

[David G4EBT]

I cut the can about 15mm above the base so that leaves a lip into which to insert a sleeve, which I make from a strips of thin gauge aluminium sheet, which I fix into the base with epoxy cement. I leave the base intact and drill 1mm holes in it through which to pass the wires from the cap to wrap around the existing solder tags. I apply epoxy to the upper part of the sleeve and push the can over the sleeve to secure it. I've done quite a lot like this.

A pipe cutter makes a neat job, but if you don't have one you can uses a junior hacksaw. If you wrap a piece of insulating tape around the can at the point at which you need to cut it, it gives a better guide than trying to draw a pencil line around the tube. You can uses a fine file to neaten up the two ends of the cuts and to remove any burrs, or rub the ends on a flat piece of wet and dry abrasive sheet.

The two capacitors in the pictures below are nut-fixing ones, but the same process can be used whatever the type, so long as the base of the can is left intact. As the can on the second example was shabby, I polished it up and made and fixed a water-slide transfer. (Some may argue that's a step too far and 'destroyed the patina'. It's an eighty year old capacitor - not a 250 yr-old Chippendale chair).

[ronbryan]

Thank you everybody for your helpful suggestions. I'll have a hunt around for 25mm tubing or thin shim and try cutting the can off neatly.

Ron

[Nanozeugma]

Originally Posted by David G4EBT

I cut the can about 15mm above the base so that leaves a lip into which to insert a sleeve, which I make from a strips of thin gauge aluminium sheet...

Hi David, may I ask what width and thickness of Aluminium sheet you use to make the sleeve - and possibly a supplier of same?
Many thanks.

[FrankB]

There was a company here in the U.S. DK Enterprises(?) that used chrome plated sink drain pipe for the new can. They had the twistlock bases and a punched piece of chromed brass for the top. They looked splendid and each was made to order. You could specify which cap which went to which lug. I used to rebuild TV sets and radios for a living & ordered from them all the time.
I have built similar re-using the base.
I have not seen them around for a long time, but also HayseedHamfest.com makes them up too. I have never used them.

[Cobaltblue]

Originally Posted by Nanozeugma

Hi David, may I ask what width and thickness of Aluminium sheet you use to make the sleeve - and possibly a supplier of same?
Many thanks.

I have used drinks cans to supply the aluminium for this sort of project

You can cut it with a pair of cheap scissors but wear gloves it's sharp!

Cheers

Mike T

[David G4EBT]

Originally Posted by Nanozeugma

Hi David, may I ask what width and thickness of Aluminium sheet you use to make the sleeve - and possibly a supplier of same?
Many thanks.

I use 1mm thick sheet. You can buy it cheaply on e-bay - for example, a 250mm x 250mm sheet of bendable grade aluminium, £2.33 post free:

https://www.ebay.co.uk/itm/Aluminium...-/271210657802

Thin enough to cut with scissors if need be, and you only need a strip about 3' to 4" in length x 1" wide for a typical cap so a 250 x 250mm sheet will be enough for maybe 20 or so caps. As it's 'bendable' grade, it's malleable so you can roll the strip with your fingers around the old can as a former, then cut one end so that when the ring is squeezed together, it fits inside the can as shown in the pics in my earlier post.

(That grade is too soft for other applications such as making brackets or whatever).

Hope that helps.

[Nanozeugma]

David: Many thanks.
Mike: Much obliged.