Capacitors "Black Museum"

[dazzlevision]

Hello,

Following on from recent discussions here about the short lives of 1950s and 1960s paper dielectric capacitors, I have assembled some pictures of such components, grouped by brand.

These were taken from my box of faulty components that I have removed from equipment over the years (my "black museum").

They show the evolution of capacitor technology. Unfortunately, the British based consumer product capacitor manufacturers (Dubilier, TCC-Plessey and Hunts-Erie) all seemed to disappear by the late 70s/early 80s. The only exception I know of is "LCR", which make the yellow axial Polypropylebne dielectric types I use in TV boost circuits. However, I've not been able to track their location down.

The only reasonably long lived Plessey (originally TCC) paper cap that seems to survive in long term storage is the grey plastic cased ones that started to appear around 1970, displacing the previous yellow cased "Supamolds" and "Duomolds". Does anyone have a spec for these, to confirm the dielectric used and the encapsulation material?

I have also attached a Word document with the same pictures but with labelling.

I've come across, but don't have examples of, other types such as the "Plesseal" by Plessey. Does anyone have a picture of this type?

Apart from the 1970s grey Plessey and the Mullard C296 "mustards" (and their Lemco or SRC clones), I would advise that all the other types are replaced on sight.

Regards,

Dazzlevision

[dazzlevision]

More Word documents

[G6Tanuki]

An extremely interesting list...!

Wondering if anyone can refresh my memory about who made a particular type of capacitor I came across a lot in 1970s-era telephone exchanges. Usually low-value (up to 0.5uF) 250VDC working. Axial leads, hard green plastic encapsulation. Something very similar in appearance was used in the first generation of domestic plug-and-socket BT NTE boxes. They looked very much like a darker green version of the green Supamold so I'm thinking TCC.

The only time they ever failed (and we had hundreds of thousands of them in service) was when the overheads took a lightning-strike - and then you usually had other issues [I remember an entire house - six extension outlets - with the entire CW1306 wiring completely vapourised] to worry about rather than an exploded capacitor.

Also, the red-and-black-plastic early-1960s Plessey electrolytics used in transistor circuits - I'm rebuilding a piece of test-gear that has more than a smattering of these. Are they "Replace-on-sight" or do they survive well?

[Station X]

All the Red/Yellow/Black Plessey Electrolytics I've come across have been bad. Perhaps I've been unlucky though.

I'm surprised to see a Mullard Mustard featured. I've never found a bad one.

[turretslug]

Originally Posted by G6Tanuki

Wondering if anyone can refresh my memory about who made a particular type of capacitor I came across a lot in 1970s-era telephone exchanges. Usually low-value (up to 0.5uF) 250VDC working. Axial leads, hard green plastic encapsulation. Something very similar in appearance was used in the first generation of domestic plug-and-socket BT NTE boxes. They looked very much like a darker green version of the green Supamold so I'm thinking TCC.

Ashcroft?

[Andrewausfa]

Originally Posted by dazzlevision

The only exception I know of is "LCR", which make the yellow axial Polypropylebne dielectric types I use in TV boost circuits. However, I've not been able to track their location down.

Rassau in Wales

[G6Tanuki]

Originally Posted by turretslug

Ashcroft?

They could very well have been Ashcroft. What I do know is that four 0.5uF 250V ones wired in series/parallel without benefit of any voltage-equalising resistors worked just fine for several years as the main energy-storage capacitor in a capacitor-discharge-ignition system I built for my Mk.1 Ford Escort.

[I think the design was published in "ETI" sometime around 1975]

[G6Tanuki]

Originally Posted by Station X

All the Red/Yellow/Black Plessey Electrolytics I've come across have been bad. Perhaps I've been unlucky though.

Given that you've sown the seeds of doubt, I'll replace the lot, probably with some nice translucent-blue-sleeved Mullard/Phillips ones (which never seem to fail).

Originally Posted by Station X

I'm surprised to see a Mullard Mustard featured. I've never found a bad one.

Only time I've ever had one fail was when the speaker voice-coil failed open-circuit and the 'mustard' tone-correction capacitor across the output transformer primary lost the will to live. An ECL86 also lost its life in that particular incident.

I've got a nice collection of 400V rated NOS mustards that I use to replace waxies in general decoupling, bypassing and "that capacitor" service.

[dazzlevision]

Originally Posted by G6Tanuki

An extremely interesting list

Hello,

Glad you like the thread!

I have some axial capacitors of a dark green colour made by TMC (Telephone Manufacturing Company - later Pye TMC). Otherwise, Filmcap - Advance Filmcap - Gould maybe?

As for those red/black case with yellow adhesive label Plessey electrolytics; if they are in low temperature transistor equipment, they may well be OK but if in a valve radio or TV, I would replace them all.

Regards,

Dazzlevision

[dazzlevision]

Originally Posted by Station X

All the Red/Yellow/Black Plessey Electrolytics I've come across have been bad. Perhaps I've been unlucky though.

Hello,

Yes, failure of the Mullard C296 series is verty rare and I have only ever replaced a couple over 40+ years of repairing/restoring vintage equipment.

I included them, to show the change/evolution of the Philips black wax dipped paper capacitors into the very reliable C296 Polyester dielectric types that replaced them, including the green cased ones that first appeared and the "clones" made by SRC and Lemco (which also seem to be reliable).

I may well add another post with pictures of electrolytics in my "black museum".

Regards,

Dazzlevision

[dazzlevision]

I forgot to mention that Dubilier (DCC) = Dubilier Condenser Company. Their very small capacitors (shown at the bottom of my "Dubilier" photo) were only marked with "DCC".

[af024]

Thank you for this posting Dazzlevision. Putting everything in one place, together with a detailed description is just the job.

I don't know whether my contribution below is of any use (maybe not as some capacitors are seemingly not identified regrettably), but there are a couple of Aerovox amongst them.

Regards,

Andy

[AC/HL]

I don't think the encapsulation makes a lot of difference, it's the dielectric that counts. The moisture gets into them all, even high grade ones, eventually. If it's paper, survival is just a combination of lucky factors.

Perhaps in the case of the Plessey electrolytics, the encapsulation did make a difference however. Had they been better sealed they might have fared better.

[Alan Stepney]

The red/black Plessey caps with the yellow labels were considered rubbish at the time they were new.
We would never use them, if we could possibly avoid it.

And, that was when I worked for Plessey!

[dazzlevision]

Hello again,

I attach some more pictures and Word documents. These cover a). plastic cased electrolytics that have proved less long lived/unreliable than others of their era. I also cover some additional paper dielectric types and a few "overseas" electrolytics.

I think the "CRL" (inside a diamond) branded black cased radial electroytic is Centralab (USA); perhaps someone can confirm this. I'm not sure about the "Impec" and "Elcap" branded ones though; any ideas?

Perhaps the mods might change the thread title to Capacitors "black museum"?

Regards,

Dazzlevision

[threeseven]

Mention is made of LCR capacitors in the opening post, I use their motor capacitors.
They are based in Wales,
http://www.lcrcapacitors.co.uk/default.htm

[AC/HL]

Title changed as requested

[AC/HL]

We have regular posts querying capacitor types/makes and related reliability issues. This comprehensive thread is well worth bumping for newer members' information

[kalee20]

Wot! No transparent-epoxy encapsulated Rifas?

[Lucien Nunes]

Originally Posted by dazzlevision

Apart from the 1970s grey Plessey and the Mullard C296 "mustards" (and their Lemco or SRC clones), I would advise that all the other types are replaced on sight.

We had a discussion here: Tropyfol experience in which the Wima Tropyfol M was agreed to be a highly reliable cap. I have since tested many more of these and found them all to be excellent, and would be happy to retain them even in relatively critical positions for the time being.

I suspect that my next restoration candidate has a few hundred of assorted values, which will provide a useful sample size to corroborate.