Electrolytic Taxidermy

[murphyv310]

Hi
Most collectors don't run their sets for long periods so restuffed caps should be reliable.
The example I gave was a radio that is used every day at work and is often left on overnight or even at weekends.
I usually use 105 degree caps and avoid ones with obscure names, Panasonic were good but even their quality has dropped since being made in China.#
Cheers
Trevor

[Retired]

Hi, for members unfamiliar with pipe cutters or wonder what they are I hope this is of use. These are two of mine and their use is to cut copper tube in plumbing. A larger size is needed for electrolytic caps and as an example a 12.7 - 44mm should be ample. These pipe cutters are readily available and with a quick web search I found; http://www.plumbworld.co.uk/pipe-cutters-616-0000 advertising this size at £12.47. Cheaper ones can be bought. They are extremely simple tools to use; the jaws are opened; the capacitor is inserted aligning the cutting wheel at the desired place and the jaws are gently closed to just nip the cap; holding the cap in one hand the pipe cutter is rotated with the other hand, by rotating and applying pressure bit by bit the cut is completed. Applying too much pressure will deform the cap so steady does it. Col..

[GrimJosef]

Originally Posted by OldBoffin

... I am very concerned that the purpose of using a large Ali can originally was to dissipate the heat resulting from the high pulse currents with associated ESR, has been lost. There does not seem to be any way for the heat from much smaller new capacitors to be dissipated, with resulting short life of the new components!
Maybe some-one would like to comment from extended trials.

I guess there haven't been too many extended trials of stuffed capacitors, but maybe this counts as one ? I've just opened up a large 800V, 8uF TCC can with a view to restuffing it and found inside, guess what, two much smaller unmarked ones (presumably 400 or 450V, 16uF) in series ! The outer can seems to have been unopened since new (March '53). As far as I can tell TCC made very little effort to increase the thermal conductivity between the inner and outer cans. The inner ones are centred, roughly, with a tube of corrugated card. A small amount of wax has been poured in, perhaps to hold things still and stop the connections from failing due to fatigue ? I don't think it will have helped much thermally. You can see from the final picture how little contact there was with the inner cans and the cardboard tube.

Unfortunately I can't tell how long this cap worked for, but clearly the people who made it thought that this was a "sound" thing to do. On the other hand this is a low value capacitor, so presumably subject to relatively low ripple current, and I note that the whole thing is only rated to 60 C. Maybe they were covering themselves .

As you can see, this is a screw-terminal capacitor so I don't have the option of pipe-cutting it and hiding the trauma with a clip. I've therefore fairly carefully "unpeened" the bottom end and removed the bakelite terminal and the internals that way. Whether I can get away with re-peening (?) it remains to be seen, but at least with this design the peened surface is pulled hard down to the chassis and will be hidden.

Cheers,

GJ

[Billy T]

Originally Posted by OldBoffin

Unfortunately I can't tell how long this cap worked for, but clearly the people who made it thought that this was a "sound" thing to do. On the other hand this is a low value capacitor, so presumably subject to relatively low ripple current, and I note that the whole thing is only rated to 60 C. Maybe they were covering themselves .

It probably didn't survive very long at all as the durability was suspect even before it was hidden away. When servicing Radio & TVs in NZ back in the 1970's it was not without good reason (and considerable provocation) that we referred to TCC as the "Treacherous Capacitor Company". They were closely followed on my blacklist by the "Unreliable Capacitor Company", and Hunts had their own unprintable sobriquet. The coming of Japanese quality components ended the cycle of regular replacements, especially for voltage doublers, just in time for CTV to arrive on the scene, bringing with it the Thorn 3500 chassis (TX574) which introduced us to a whole new world of unreliable components. Made for good overtime work though, and more than compensated for the steep drop in monochrome service.

I do wonder a bit about the wisdom (and value) of capacitor stuffing, especially since the under-chassis is not likely to be revisited very often. Very few radios that have seen normal service have all original parts anyway and most repairs have seen replacement parts from the stock shelf, not the manufacturer. Subsequent owners of restored equipment are very likely to assume that the old caps are just that and replace them again. Pasting a note inside the cabinet or on the inside of the back advising that they have been restuffed might be a good move.

Cheers

Billy

[beamcurrent]

I guess there haven't been too many extended trials of stuffed capacitors, but maybe this counts as one ? I've just opened up a large 800V, 8uF TCC can with a view to restuffing it and found inside, guess what, two much smaller unmarked ones (presumably 400 or 450V, 16uF) in series !

I have often wondered how that type of capacitor did it's voltage rating, 450/500 volts being the normal maximum for an electrolytic. Thanks for saving me having to open one up!

Brian.

[GrimJosef]

Given how much space was wasted inside the can I also think it's quite funny that in their adverts (see the attached one from a 1955 Practical Wireless) TCC made a big deal of how much space this design could save. Of course they did need to find some way of keeping people's fingers away from the second electrolytic, whose can is at half the HT voltage. So I guess they had little choice. And I'm sure they were right when they said that the result would be smaller than a similarly rated paper-in-oil unit.

I'll be re-stuffing mine with modern plastic-cased polypropylene motor-run caps. They're "only" rated at 475V AC (3000 hrs) which corresponds to 670V DC. But that's plenty for my application and they shouldn't be nearly as lossy or degrade nearly as quickly as electrolytics.

Cheers,

GJ