Not necessarily AC. In my Sherwood S1000II (36 watt 6BQ5 amp) a former tech did not change the electrolytic in the preamp section. It started as a low grade hum and got worse and worse. Understand that this a high hour use amp as it's my center channel amp for my HT system.

I pulled the unit down and found that the old electrolytic was leaking.


The ironic thing is that CEC is actually supposed to be Mallory.

I understood that CEC bought the Mallory manufacturing equipment and a bit later opened their own manufacturing line. I wouldn't call that "CEC being Mallory".

-Chuck

I didn't mean to imply that original old caps should be trusted, but I would take one over a modern off brand cap. Those often fail in less than a year of normal use. It's a waste of time replacing old caps with new ones of questionable quality. Spend a little extra and go with any reputable brand such as Nichicon, CDE, or Panasonic.

PITA. Contact Heyseed. They supply high quality caps and cost about same as CE manufacturing.

New manufactured Brand NAME capacitors are better than ever. New can types are not made, they are a can stuffed with 1/2" diameter new individual capacitors. Instead of the 30 year life suggested life of past, new caps are now rated for average of 50 years per many techs due to improvements.
However, the capacitor plague from 1999 to 2008 damaged the industry. You can look it up on the internet. Caps were made in China and had faulty electrolyte inside. You can buy US made capacitors from CDE.

Well I have been talking about this for some years now and looking at what others are doing. I'm ahead of the game here and have been for some years.

I noticed over 40 years ago that when a component failed, it was replaced and thrown in the bin. Electrolytic caps of course being the common problem. But who ever bothers to check why, where is the forensic examination of the component, who has the interest or time to do it ?

Then I got interested in why electrolytic caps were failing, some were young (<5yrs) others older >40 years.

There are a number of mechanisms of failure at least 4. However the common one is that the rubber seals allow water vapor to escape (even if they do not allow the frank electrolyte to leak as it often does). The capacitor goes high ESR and low capacity and loses physical mass. I have confirmed this many times, that the defective capacitor can also be returned to its original capacity and ESR value, by soaking it (out of its canister)in deionized water for 24 Hrs.

In any case, because of these issues, including the very destructive effects of leaked electrolyte, in my designs & restorations of tube gear now I seldom if ever use electrolytic capacitors in the high voltage power supply sections. Even the re-builds of vintage gear I go for polyester or polypropylene caps. One advantage is that vintage electrolytic caps were very physically large for the capacitance and voltage rating, and modern non electrolytics of the same uF and higher or equal voltage ratings, quite compact.

Have a look at the MKP capacitors I just used in this project, to avoid electrolytics:

viewtopic.php?f=12&t=371368

And also the photo attached of a multi section electrolytic, from a vintage TV restoration, re-built with non electrolytic capacitors, which have the same uF voltage but actually higher voltage ratings than the original electrolytics.

This might not be an economic option, but good things rarely are.

It is quite common to do a restoration on tube apparatus and if its done with electrolytics, to see them fail again in less than 5 to 10 years. So it needs a different approach, unless you think that is ok, I don't. In the service industry it is thought to be ok, because that time frame exceeds any common guarantee period, but what if it is for your own equipment I wonder.

CEC may not have gotten the intellectual property

Manufacturers usually have research labs that do forensics on their products. One such capacitor company found that even the smallest amount of "chlorides" contaminated the manufacture of a quality electrolytic capacitor, dramatically shortening the life. At the time was with a 1940's lab...

Similar "contamination" finds its way into the manufacture of Lithium traction batteries, usually dooming the cell to failure within months, I was not privy to the nature of the contaminate in that instance.

That said, "rolling 'ur own" caps does not apply like a cigarette...

YMMV

Chas

You are quite right about this, halides of any kind are a disaster inside the Electrolytic Capacitor. Some capacitors fail due to likely Halide contamination of latex rubber. Here is a fine example of it pictures of the insides of some electrolytic caps that went open circuit due to full thickness corrosion of the interconnects inside, this is one of the other mechanisms of failure aside from drying out, I have photos of most of the failure mechanisms (there is one for example that short circuits the capacitor too):

http://worldphaco.com/uploads/ELECTROLY ... FRAMES.pdf

As I say I have been inspecting failed electrolytic capacitors for decades, which is why I generally don't use them for my restorations and projects, if I can find a way to avoid them.

Multi section E caps were part of the hum control system
designed into the amplifier. You may well chop out the can
and patch individual sections in.

Will each section have the same ESR ? Trace the ground loop
in some amplifiers and you may see it starts at the Multi can,
and threads through terminating at the phono plug array.

Additionally the multi cap shields the sections all together
and keeps them away.

Bitter memories of trying to sub an original cap with
individual sections only to have customer ship it back
to factory service to have it restored to what it was.



Below is a very old Heath A 7 D amplifier.

Consider what went into hum reduction. How many
prototypes did they they try ?

Heath kit A7 D

Hello Steve,
I agree equipment like heathkit they put in a lot design and engineering in to why and how a product works .

Anyway I have had really good luck with nichicon caps and Sprague but Sprague are getting more expensive

Apart from a few incidents (the bulging cap plague that was mentioned, early SMD electrolytics, and 1980's switching power supplies) name brand caps last a long time. It's rare for me to need to replace a Nichicon, CDE, or other quality cap that's less than 30 years old. Even at 30+ years, most of them are still good.

On the other hand, I have a large box under my work bench that's brimming with hundreds of Cap-X-on, and Teapo caps from computer power supplies. Those same power supplies contain a small number of name brand caps which are invariably still good.