Fix Old Caps, But Keep That “Can Capacitor” Look | Hackaday

2022-11-03 15:44:37 By : Ms. vivian zhang

Vintage electronics and capacitor replacements tend to go hand-in-hand. Why? Because electrolytic capacitors just don’t last, not the way most other components do, anyway.

It’s one thing to swap old caps with modern replacements, but what about electronics where the components are not hidden away, and are an important part of the equipment’s look? [lens42] shares a method for replacing antique can-style capacitors in a way that leaves them looking completely original. All it takes is some careful application of technique.

The first thing to do is carefully file away the crimp of the metal can until one can release the ring and plate that hold the terminals. Once that is off, the internals can be pulled from the metal can for disposal. Since the insides of the old cap won’t be re-used, [lens42] recommends simply drilling a hole, screwing in a lag bolt to use as a handle, and pulling everything out. There’s now plenty of space inside the old can to hold modern replacements for the capacitor, and one can even re-use the original terminals.

That leaves the job of re-crimping the old can around the terminal ring to restore a factory-made appearance. To best do this, [lens42] created a tapered collar. Gently hammering the can forces the bottom into the taper, and the opening gradually crimps around the terminal ring. It’s also possible to carefully hammer the flange directly, but the finish won’t be as nice. This new crimp job may not look exactly the same as before, but once the cap is re-installed into the original equipment, it won’t be possible to tell it has been modified in any way.

If this sounds a bit intimidating, don’t worry. [lens42] provides plenty of pictures. And if this kind of thing is up your alley, you may want to check out the Caps Wiki, an effort to centralize and share details about tech repair, especially for vintage electronics.

Please be very careful with old large capacitors. They likely contain PCB’s. I am an “old timer” electronics engineer and have seen workmates pass on due to “unexplained” cancers. See

Electrolytic capacitors won’t contain PCBs. Some other types might if they are old enough.

Oil filled caps and transformers are what to be afraid of because of potential PCB’s in them. If you question whether they are oil filled or eletrolytic look for the solder blob that seals the can. Here you can see the solder blob between the terminals near the edge of the can that the oil is filled through. Automatically assume anything from the 1980’s back may have PCB’s.

Way to scare people. This article is about electrolytics. PCBs were only in sealed metal cans. Those are less likely to need replacing anyway. I have some in the basement, ceramic insulators on top. Been there for fifty years, were old then. Perfectly safe unless they are broken, or I try to open them.

They may not even contain PCBs. My recollection ism they were regular oil, then PCB, then something else, so you can’t be sure.

If I recall not all “PCBs were only in sealed metal cans”, and there were several materials that used it as a fire retardant. It was common to see old paper foil capacitors use PCB instead of regular mineral oil, but also many phenolic paper parts as well. Note, PCB were in a family of different products, and not all were a liquid oil form.

If you ate seafood from polar regions, there is a high probability you have already ingested some trace PCB in your life. The process of contamination migrates as animals that feed in these regions see bioaccumulation in fatty tissues up the food-chain (each stage concentrates by around 10x). There were some beluga whales so contaminated at the time of death, they were buried as toxic waste.

I don’t think the poster was trying to scare you with a non sequitur, but rather dissuade young people from doing something irresponsible. The stable chemistry of PCB is very interesting, and worth learning about as a cautionary tail of what seemed like a reasonable solution at the time. =)

It’s the young people who need to worry the most. I worked for the BBC as a transmitter engineer back in the 80’s and there was a big move to get rid of components containing PCBs from the old equipment going back to WW2 days. We were told that one of the critical effects of PCBs was on your testicles and it could lead to deformities in the children you had not concieved yet. A horrifying prospect and one the BBC protected against during the removal process by recruiting volunteers from the older staff members who had already had all the children they were ever going to.

I worked for a large telco and there was special requirements for working with those caps. I would not touch them, not worth it.

I fully agree, too. Old capacitors were dangerous, sometimes, even. I’m thinking of paper condensers.

Other items “fixed” like this were anode batteries or electron valves that acted as a diode. In the process of restoration, the innards were replaced by modern parts:

The chasis of the 90v anode battery was filled by 10x 9v batteries in series. The burned-out valve (diode) was opened carefully and a glass diode was soldered in place. Of course, there are pro/contra arguments for this modification. A glass diode wasn’t necessarily better suited as a real valve. The characteristics of the valve could have been superior. But as a quick fix, it was fine.

Silicon diode has a voltage drop of less than a volt, while vacuum diode rectifier might have dozen volts or more. End result: significantly higher anode voltage after rectifier, which might cause some unpredictable results in the operation, especially long term.

Thank you a lot for the information! ??

Another issue might be that really old tube radios (all power radios) were built for lower voltages. They had settings for 110v (DC times?), 220v, 230v (*maybe*) but not 250v. Using them in a modern light grid could cause unpredictable results, maybe. Some vintage enthusiasts either modify their radio sets and record players or use a separation transformer to simulate an old light grid. Maybe that’s even better, due to heavy fluctuations and ripple in today’s grid.

there were a lot fewer capacitive or Rectifier-capacitor (rectipacitive?) loads Back Then, everything would have been a much more linear or purely inductive load. modern power grids have so many rectipacitive loads that the waveform can start to look more like a square wave due to the rectipacitive inrush of thousands of computers and phone chargers and LED drivers (etc) clipping the tops, and that can play merry hell with purely inductive-resistive devices like tube amp radios

Choke input filters were rare due to cost, unless they used a wound field coil on the speaker. The slow startup and high drop of a tube rectifier usually did the job. If you replace with a solid state diode, put a power resistor in series.

CE Manufacturing Bought out Mallory’s old can cap tooling and is making new can caps to the specs of the old can caps. This is another option.

To save others the trouble of looking them up:

don’t forget to mark the recapped capacitors as recapped and with a date so future people will know what happened.

Because in Hackaday 3.0, commenters will complain “The uncouthe bahstahds gutted the part and put other parts in it, instead rebuilding the original in a replicator!”

Um, I guess the idea behind this was that capacitors do age and must be replaced once in a blue moon. So it makes sense to attach a note that says when the capacitor was serviced the last time. Knowing that it this a new capacitor in an old shell and not really a vintage part is good to know in that context.

With Hackaday 3.0, will we be able to edit?

High quality computer power supplies have power factor correction circuits that reduce the clipping effect. This has been a part of the Energy Star standard for more than a decade.

I usually just leave the can as-is on top of the metal plate and clip the leads and wire in tiny modern caps underneath it where the rat’s nest of wiring lives. Got lots of nice tubes and cans on display, even if the cans aren’t wired up to anything anymore.

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