Capacitor case rebuild.

[Testgear John]

I'm sure some old hands may well have beaten me to it, but a good quality pipe cutter makes a great job of slicing a tubular can capacitor case ready for hiding those modern caps.
In this case, it's an old Pilot cap, but it has the bottom threaded mounting that will fit my PYE G.chassis.
I will drill out the aluminium studs that were the contact posts and use wire lead-outs.
If you cut just below the waisted portion, and carefully de-burr the edges, the whole thing can be joined nicely, perhaps with araldite or similar.

[line sync]

You`ve made a very neat job of that capacitor john.
I very carefully cut my cans open using a hacksaw but they don't look quite as good as yours.
I`ll try a pipe cutter next time .

Robin

[HamishBoxer]

An excellent job.

[Argus25]

I'm sorry to completely disagree with posts 2 & 3 and what you did to the capacitor. I keep seeing capacitor canisters being damaged like this and it is a shame to do it them, when there is a far better method.

Have a read of post # 26 here:

https://www.vintage-radio.net/forum/...=143229&page=2

and go to the link to see a photo.

It is much better to remove the minimum amount of aluminium on the base surface to release the end plug, leaving the aluminium canister basically unharmed and providing a strong area with the original circumferential folds, for the new base & terminals to be fitted.

[Boater Sam]

I am at variance with both view, awkward by nature some say.
I cut them where the clamp will cover the cut but with a saw to avoid the internal burr a pipe cutter leaves, it makes pulling the guts out easier.
I then find or adapt a piece of plastic tube to fit closely into the tube to bridge the cut enabling the clamp to be tightened properly. A dab or two of contact adhesive just to hold it together whilst being refitted.
I drill the tag rivets with 30 thou drill for the capacitor leads to come through and solder them to the existing tags.
Cans with screw and nut bases I cut about 20mm up and use a band of heat shrink to cover the cut, preferably clear, with a paper label inside.
Doing them this way means the process is repeatable if need be at a later date and I preserve the existing end bungs.

To each his own, thankfully we all have our own ideas.

[Graham G3ZVT]

Originally Posted by Argus25

I'm sorry to completely disagree with posts 2 & 3 and what you did to the capacitor. I keep seeing capacitor canisters being damaged like this and it is a shame to do it them, when there is a far better method.

Have a read of post # 26 here:

https://www.vintage-radio.net/forum/...=143229&page=2

and go to the link to see a photo.

It is much better to remove the minimum amount of aluminium on the base surface to release the end plug, leaving the aluminium canister basically unharmed and providing a strong area with the original circumferential folds, for the new base & terminals to be fitted.

Hugo, I followed your advice and I cannot commend your de-stuffing method highly enough!

After weakening the lip with a file I elected to drill a hole in the bung and insert a wood-screw, which I clamped in a vice and pulled out the bung+contents. Considerable pulling force was required.

I always suspected there was a better way than cutting the can where it would be hidden by the retaining clamp. I am glad I had put this condenser to one side.

Further examination shows that the woodscrew had firmly embedded itself into the capacitor's structure.

I am of the opinion that had it not done so, only the bung would have been removed, snapping the wires and leaving the contents firmly stuck in. There is some hard debris visible in the top of the can, I suspect it is adhesive used in manufacture.

[Argus25]

Good move with the screw.

After the base plug is pulled out and sometimes if the actual capacitor proper cannot be withdrawn easily from the canister and the connecting strips that join it to the base tear off; if the center of the foil is grabbed with toothed long nosed pliers, the center will pull out as the foils uncoil themselves and it can be removed that way.That canister of yours will clean up nicely at the end with a file & some emery paper.

The more old caps you un-stuff, the less you will trust any old and re-formed caps in vintage gear, there are often horror stories hiding in the cans.

Also I have now abandoned electros for my vintage restorations and use metal can style MKP capacitors as shown in post #30 on this thread:

https://www.vintage-radio.net/forum/...=140570&page=2

Also, where its possible I re-stuff with non-electrolytics in the old cans, where they will physically fit, so that I never have to go back in there, that way the new base can be glued in with epoxy resin, rather than silicone rubber.

[Boater Sam]

Originally Posted by Argus25

Good move with the screw.



The more old caps you un-stuff, the less you will trust any old and re-formed caps in vintage gear, there are often horror stories hiding in the cans.

Hear Hear, they range from soaking wet to burnt to a crisp, always disgustingly messy.
It amazing when the can is cleaned and the new caps assembled how much empty space is left, I often think of leaving a time capsule inside.

[Refugee]

When the big caps failed in my amps I un-soldered several wires and lifted a tag strip to one side and went in with a 10mm drill through the bung and into the old foil roll in order to create holes that I filled with two 10mm diameter capacitors of the type often seen in flat screen TV sets. The things are dirt cheap even Rubicon ones from Farnell.
I had to stick a 10mm dowel in the first hole to stop the contents rotating while drilling the second hole.
The capacitors in my set were hard to get at from the top of the chassis so I did them without removing them from the amp.
A small spot of epoxy was all that was needed to stop them from falling out.

[Boater Sam]

That's another way, does preserve some originality. Beware that some of the small new caps may have the voltage rating but not the ripple rating for reservoir capacitor substitution.

[Testgear John]

Originally Posted by Argus25

I'm sorry to completely disagree with posts 2 & 3 and what you did to the capacitor. I keep seeing capacitor canisters being damaged like this and it is a shame to do it them, when there is a far better method.

Have a read of post # 26 here:

https://www.vintage-radio.net/forum/...=143229&page=2

and go to the link to see a photo.

It is much better to remove the minimum amount of aluminium on the base surface to release the end plug, leaving the aluminium canister basically unharmed and providing a strong area with the original circumferential folds, for the new base & terminals to be fitted.

I think describing what I have done as damaging the capacitor is completely over the top, actually. The label is gone, it's a metal tube, and actually if you cut it in the way I have described it is an almost invisible repair, not a butt joint!
It isn't like that once they are fitted they are subject to any particular mechanical strain.

[Testgear John]

Originally Posted by Boater Sam

I am at variance with both view, awkward by nature some say.
I cut them where the clamp will cover the cut but with a saw to avoid the internal burr a pipe cutter leaves, it makes pulling the guts out easier.
I then find or adapt a piece of plastic tube to fit closely into the tube to bridge the cut enabling the clamp to be tightened properly. A dab or two of contact adhesive just to hold it together whilst being refitted.
I drill the tag rivets with 30 thou drill for the capacitor leads to come through and solder them to the existing tags.
Cans with screw and nut bases I cut about 20mm up and use a band of heat shrink to cover the cut, preferably clear, with a paper label inside.
Doing them this way means the process is repeatable if need be at a later date and I preserve the existing end bungs.

To each his own, thankfully we all have our own ideas.

If you take your time with the pipe cutter, advancing the disk slowly and making many turns the internal burring is kept to a minimum. The old innards came out without fuss. I think some of you are missing the fact that the can fits over the " Grooved or reduced in diameter" portion quite snugly. It is not a butt joint. You could still back it up with an internal tube if you feel it is necessary.

[Refugee]

Originally Posted by Boater Sam

That's another way, does preserve some originality. Beware that some of the small new caps may have the voltage rating but not the ripple rating for reservoir capacitor substitution.

The ripple current is quite respectable on the branded ones.
The ones I used they are something like 300ma or more for an amp that takes 80ma. Any heat is conducted away by the remains of tho old capacitor better than the free air you get if you clean it all out before putting the new ones in.

[Freya]

Its safe to say that different members have different ideas on which is best for re-stuffing an electrolytic capacitor.
I have been using the filing the end and pulling the plug now since 2007, in my case usually using the same end cap super glued back in. IMHO it is 98% invisible only let down by the new lead out wires and sometimes the new metal exposed by the filing.

[Graham G3ZVT]

When restuffing the can, what is the best way to deal with the "common" terminal, when in the original it was connected internally to the can?

I can't honestly say I can see how that connection was made on the one I just unstuffed (at 0300Zulu!).

The easiest way would be to bring the common to an extra tag on the bung, that's what I did on my first attempt when I used a new can made from a aerosol can.

This time I just want the two +ve tags for originality.

I have idea involving stranded wire trapped between the inside of the can, and a strip of springy steel formed into a C shape.

Any thoughts?

[line sync]

Just wanted to reply to Argus's comments which sound's like I'm butchering my restuffed capacitors.

I do mine a similar way that Boater Sam does his, I cut the can so it is hidden by the clamp, I put either plastic pipe or metal tubing inside which is carefully selected to be a tight fit. I drill the tag rivets using a 1mm drill bit and feed the wires from the new capacitors through these holes and solder them to the existing tags and I even mask off the writing on the can so as not to wear it away whilst handling the can. I take pride in doing a neat job.

Another way to removed the innards if they don't want to come out is to use a heat gun, this works really well.

[Station X]

I've yet to find a piece of plastic pipe which is a good fir inside a can. I simply cut the pipe longitudinally in two places, then close up the gap. It takes a bit of trial and error to get it exactly right. The two sides of the gap can be glued with Solvent Weld Adhesive, but it's not really necessary.

I drill small holes immediately adjacent to the tags for the wires rather than drilling the rivets. The important thing is not to solder wires to the rivets. You generally end up with a HR or intermittent connection.

[Argus25]

Originally Posted by line sync

Just wanted to reply to Argus's comments which sound's like I'm butchering my restuffed capacitors.

I do mine a similar way that Boater Sam does his, I cut the can so it is hidden by the clamp, I put either plastic pipe or metal tubing inside which is carefully selected to be a tight fit.

Sorry to sound blunt with my remarks, it is just a point of view.

However this is the fundamental problem with cutting the can through its side wall:

Thin metal structures get their strength through creases & folds. Once you have cut the can through its side wall, especially in the region where the clamp goes, it loses its strength to compressive forces like a clamp. So as you quite rightly point out, it then requires a (preferably machined) internal cylinder, to exactly the right size, to create a strong join that won't be disrupted by the clamp (if there is one). This also uses up space in the can.

So it is really unnecessary "damage" to use that word, and then extra repair effort to get the final result, which is simply not as good as the other method which leaves the aluminium can largely intact.

I think the place to put in the extra repair work & effort is in the new base (as often the original is not fit for duty) so I normally machine one out of 1/4" paxolin or similar, and use machine screws and lugs to make new terminals.

[McMurdo]

I use the file-off-the-rim method. I've done a couple by cutting the rim in the lathe, but the last time I tried, using a modern but dead capacitor for a donor can (the original can was missing) I had trouble getting the chuck tight enough without denting the can. In any case the can worked loose and crashed into the tool, writing it off.

So its back to the file followed by araldite for me.
(a simple way of colouring epoxy black is to mix in a bit of old photocopier toner).

[Refugee]

I had a 1950s Hunts can with a bung with a Paxolin core that had gone conductive due to seeping electrolyte making reuse of the old tags useless.
This did not matter with my method leaving much of the old material inside.