Vintage capacitor revival/repacking

[mike1 ryan1]

Hi,
I have an old homebuilt radio that has a selection of capacitors all of which are way off their stated values. Is there any way of 're-forming' them such as with electrolytics, or do they need dissemboweling and new components placing inside them. If the second option is all I can do can anyone provide me with any tips they have found to remove the innards. I have done one so far , inside was foil and paper surrounded by something like pitch and it took a long time being very careful not to damage the outer bakelite case.
Thanks,
Mike.

[HamishBoxer]

Save is way is to re-stuff. Sometimes warming them up first can enable getting the contents out.

[HamishBoxer]

Dash! I meant safe,not save.

[mike1 ryan1]

Yes that's what I figured. I managed to get a reasonably good system of wrapping them in cloth and putting in a drill vise, then using a spade bit in the pillar drill removing most of the material then finishing up with a small very sharp chisel. Seems to be the best way to go.
Thanks,
Mike

[HamishBoxer]

I did a French set out of interest once,and found the caps got warm enough (as they were leaky) just to pull the contents out very easily.

Possibly a gentle warm in the oven may work as well. Yes,it is a fiddle but worth it in the end.

[60 oldjohn]

Originally Posted by mike1 ryan1

Hi,
being very careful not to damage the outer bakelite case.
Thanks,
Mike.

Hi Mike, if the worst happens I have a selection of these in similar condition, a second chance if you like.


John.

[Refugee]

I would use an old electric cooker plate with about 30 volts applied.
Just take all the nuts off the terminals so that they can be pushed down with a stick to get all the stuff out of the casing once it has warmed up.

[christge]

I like restuffing. My method is toaster oven. I suspend the component from a rack in a high slot, use a paper clip to hang it by the casing. The innards drop onto the bottom plate which is Iined in Aluminum foil for easy cleaning. Works a treat.

Pitch dissolves in white spirit, just leave them in a tub of it for a while (a week or so).

[Ed_Dinning]

Hi Mike, be careful with the heating as Bakelite can blister easily. They are usually fixed in the case with bitumen that will allow them to be pulled out when warm.
plenty of room inside for modern parts, note these are not normally electrolytic caps.
reseal with candle wax is it is less messy than bitumen

Ed

[M0FYA Andy]

Sugru would be ideal for resealing this type of capacitor after restuffing.

Andy

[PJL]

Freezing makes the tar brittle. It can then be chipped out but don't do it in the house as the chips go everywhere

[mike1 ryan1]

Is my preferred type of capacitors to use when re-stuffing? I have some 1uf polypropylene types for the 1 and 2uf larger types, I guess they are ok, there are some smaller value, 0.0003 and 0.0001 types to re do too. What about ceramic disk, are they ok to use? Just thinking of using what I have already.
Thanks,
Mike

[mike1 ryan1]

Hi John,
Thank you very much for your offer, I have managed to get them all out with only one very small hairline crack happening to one of them. The last one was a different type with mainly wax inside surrounding everything. This one came out in one piece after heating with a small heat shrink gun.
Thanks,
Mike

[Mike. Watterson]

If the voltage rating is Ok, then ceramic are fine.
On some Bakelite paper caps I simply cut one connection and added the small ceramic capacitor beside the original and then resealed.

[mike1 ryan1]

Brilliant thanks I'll have a root through what I have before I order anything new.
Mike