Restuffing a double capacitor.

[Radio Tech]

I know this might seem daft in asking but the high voltage capacitor pictured below is out of the 9 inch TV that I am restoring, the problem is how do or what is the best way of getting the top off this in order to re stuff the capacitor and bearing in mind that this is going to deal with 6kV. Is that top sweated on by some means and if it is how do I apply heat to melt the soldered joint.

Regards

Ken

[Station X]

My guess is that the top has been crimped and soldered much like a can of beans. You'll have great difficulty in unsoldering it with a soldering iron. A blow torch will be needed to melt all the solder simultaneously.

It would probably be easiest to cut the bottom off the can and pull the guts out that way.

A tin opener? the lid will resolder quite well.

[Radio_Dave]

It looks high quality. Are you sure it's no good?

David

[Station X]

If the bottom can be removed leaving the fixing lugs intact, then the bottom can be discarded after restuffing. It only serves to keep liquid in. I did this with the bathtub capacitors in my AR88.

[turretslug]

This may be bordering on tedium, but take care about coming into contact with the insulating oil- old and possibly decomposed oils generally are not good things to get on the skin. In particular, some capacitors contained PCB oils (Dubilier were US-based and they were widely-used there) which are particularly insidious in their toxicity- being highly soluble in lipids and near-insoluble in water, it's been quipped that it's safer to drink the stuff than handle it, though neither are recommended! The jury is out as to whether commonly-available protective gloves are any use and the wrong choice may just spread it further over the skin.

If you feel you have to open it/them up, just handle in a way that involves minimum spillage/smearing and particularly avoid getting it on yourself.

[Radio Tech]

Thanks everyone for the tips and suggestions, in answer to David's query I only suspect one half of the capacitor has gone leaky at its working voltage because the series resistor burns, but I have no way of testing this properly as my AVO bridge can not produce 6kV. I think Grahams suggestion would be something to try but instead of the bottom off I would take the top off with a hack saw, the bottom is used to bolt it to a plateform. I might get hold of Mike Barker as he has had dealings with this sort of thing and may be able to prove if the capacitor has gone on one side. Bit of a problem as I would like to prove the capacitor before I get too involved. Keep you posted

Best wishes

Ken

[Station X]

Originally Posted by Radio Tech

Thanks everyone for the tips and suggestions, in answer to David's query I only suspect one half of the capacitor has gone leaky at its working voltage because the series resistor burns, but I have no way of testing this properly as my AVO bridge can not produce 6kV.
Best wishes

Ken

A bit drastic I know, but can you not swop the connections over and see whether something else smokes?

[stevehertz]

Applying logic. If you're going to the trouble of restuffing that cap, then clearly cosmetic issues are important to you. That said, if you apply any form of heat to that can you're going to ruin the paint finish, and practically speaking, those folded, soldered joints will be a nightmare to open anyway (I've been there), and the whole act of trying to pry open the joints will render the can looking totally messed about with and ugly - it will be screaming, "I have been opened up and re-stuffed", totally negating the purpose of the exercise.

So, drill into the bottom of the can and remove all innards, restuff with new caps. Use insulation tape to make sure nothing comes into contact with anything that it shouldn't. When bolted in place you will not see any sign of the can having ever been opened. You could even cut a piece of tinplate to size and just 'dog' it in place with solder to the underside edge that was not removed by the drilling. Alternatively cut a piece out of an aluminium can and glue it in place - again it won't be seen. Job done, perfect result if done carefully.

[Radio Tech]

Thanks Steve for that information, yes I suppose it would be better to take the guts of it from the bottom but I would of course have to make sure the replacement caps are soldered properly to those top connections, reaching them may be a bit of a problem though but I will see, not yet got the new ones should be on their way to me soon. Let everyone know how I progress..... Regards Ken

[60 oldjohn]

Don't try to solder inside case, it will be near impossible and the caps will be in the way. Drill a small hole down the sides of terminals, thread capacitor wire through hole from inside, thread some silicone sleeving down wire from outside through hole until it will not go any further then wrap wire around terminal. You may not need to insulate the earth wires. Try to drill hole in a position where it will be hidden under the connecting wires. Once in set the wires may be soldered Once with the connecting wires to the original posts. If you were able to solder wires inside the old cap case there would be a good chance they will detach when soldering the connecting wire in place.

John.

[Refugee]

It looks like with the bottom plate completely cut back to the edge seam the guts might just slip out with the terminal nuts removed.

[stevehertz]

Originally Posted by 60 oldjohn

Drill a small hole down the sides of terminals, thread capacitor wire through hole from inside, thread some silicone sleeving down wire from outside through hole until it will not go any further then wrap wire around terminal. You may not need to insulate the earth wires. Try to drill hole in a position where it will be hidden under the connecting wires. Once in set the wires may be soldered Once with the connecting wires to the original posts. If you were able to solder wires inside the old cap case there would be a good chance they will detach when soldering the connecting wire in place.

Good idea John. Nonethless in the past I have wrapped heavy gauge copper wire around the bit of a cold soldering iron and cut it off with a (say) three inch tail or point that can be bent to an 'L' shape (or whatever) to access far corners. When the iron is hot, melt some solder around the copper wire to further enhance the heat transfer. You can then point this 'anteater' soldering iron into difficult to reach places. When you've done just remove the wire with pliers whilst the iron is still hot. It works, I've done it.

[Station X]

As the set this capacitor comes from is being offered for sale in the fourms, I'll close this thread:-

https://www.vintage-radio.net/forum/...d.php?t=122418