Slighty Uncommon Capacitors From The Bits Box

[Radio1950]

I was rummaging through my bits boxes and found some slightly uncommon types for your possible interest.

These are mostly 1960s silver mica HV types from Steafix of France.

The multi element tubular ceramic is an LCC 3x1000pf.

The tolerance on the square ceramic amused me.

The tiny bluish mica is what I was rummaging for; a 1% silver mica cap from ITT, originally used in timing circuits.

Does anyone have a 1960s Steafix Catalogue in PDF please?
I would love to reminisce.

[DMcMahon]

Originally Posted by Radio1950

The tolerance on the square ceramic amused me.

I cannot clearly read it from the photo, does it say 130% ?

David

[Radio1950]

Sorry about that.
JPG size limits.

[PJL]

0-0,2uF does seem a generous tolerance. They could manufacture them with nothing inside and even then it would read as a few pF.

[Jon_G4MDC]

0 to 100% is 0.1 to 0.2 uF or?

[DMcMahon]

Yes that is how I would read it i.e. 0.1uF +100%/-0%

Does seem strange that with such a large +ve % tolerance that there is no -ve % tolerance.

David

[turretslug]

That's my thinking, too- "With this capacitor, you'll get at least 100nF, you may get as much as 200nF". It's fair enough that a designer might be after "at least" in a decoupling situation.

[Skywave]

I'd be inclined to try to measure its actual capacitance - there are various ways of doing that - and marking that capacitor accordingly.

Al.

[Jon_G4MDC]

I think the "won't be less than" approach is quite useful.

[Radio1950]

Better photo of some items.

All the 0.1uF ceramics measure about 0.12 uF, and all are slightly leaky even at 150 V DC.
Measure 20 -30 megohms on a DVM.

The Triple Ceramic 3 x 1000 pfd measures approx 800 pfd each section to end, and each terminal measures approx 370 pfd to any other except the end.
Test OK on 400 V DC for leakage.
They were used in a radar 30 MHz Log IF Amp.
One section for cathode bypass, one for anode, one across the filament.

The little blue 700 pfd 1% cap measures 708 pfd, which is within the measurement uncertainty of my LC tester.
Tests OK for leakage on 400 V DC.
certainly a good capacitor.

All the capacitors are from the 1960s.

[Radio Wrangler]

The name 'Steafix' makes me think of steatite, a magnesium silicate ceramic, one of the porcelain family. OK, it's just the name of the company, but it may be an indication of where their roots lie.

100nF is awfully big for a mica part, and mica capacitors tend to be pretty stable and are usually made to narrow tolerances easily enough.

-0 to +100% looks like an early ceramic.

I've known pF range piston trimers with steatite ceramic dielectric. Very stable, and very linear (low intermod). There is a company in Britain by the name of Steatite Ltd making various things from the stuff.

Porcelain capacitors are common enough in the RF transmitter business. ATC (American Technical Ceramics) and Dielectric Labs inc. make amazingly tough RF capacitors used in high power density transmitters that take RF currents which would destroy normal types. I used to put 300W pulses through 100pf ceramic '100A' types close to the size of 0805 surface mount packages. Again these are the sort of thing you may find in stacked groups to several nF but their tolerances are normally tight. So they're not related to 100nF -0 +100% sort of things. Expensive and used only where necessary.

I think the capacitors are evidence of a firm which has expanded outside of a type of product which named it.

David

[MotorBikeLes]

David, when I saw "Steafix" I also thought of "Steartight and Porcelain", a ceramic manufacturer. I am pretty certain I went on a factory visit there with tech probably around 1964. I can't recall where, but it could have been near Worcester.
Regarding mica caps, generally small values as you say, but BTH used to install one of around 0.16UFd in a device used in a field I am not allowed to discus here. Very reliable, and far better than the non-mica types used by Lucas, whose devices failed far earlier due to capacitance breakdown.
Les

[Radio1950]

I cannot find the origin of the Steafix company which merged with LCC.

My square ceramics are probably LCC type DQX731, (or an earlier version), available in two tolerances +/-20% and 0/+100%.
I would think that the latter tolerance arises against a spec requirement for a bypass cap with a minimum figure, and allows for manufacturing spread.
This has been alluded to by others in this thread.

See attached page from - Composants_electroniques_miniatures_[J.PEYSSOU_1968_577p].pdf

Available at
http://www.retronik.fr/Composants

While I was searching for this I found an interesting spec sheet for Beehive Capacitors which I have never seen before.
I wonder who made them first?
We always called them Philips 3-30 capacitors.
.

[MotorBikeLes]

Internet searches can be confusing. i searched for "The Steartite and Porcelain Company" and got rubbish. When I tried "Steartite and Porcelain Ltd.", many hits. This one https://www.teleramics.com/makers/spp.html confirms my memory of the company, near to Worcester, later becoming Morgan Advanced Ceramics Ltd. I recall now it was large (no, massive) porcelain insulators we went to see. I assume the ceramic capacitors came later under the Morgan banner.
Les.

[Maarten]

Originally Posted by Radio1950

While I was searching for this I found an interesting spec sheet for Beehive Capacitors which I have never seen before.
I wonder who made them first?
We always called them Philips 3-30 capacitors.

The attached specsheet originates from the component division RTC of Philips France, I don't know of any other manufacturers besides Philips who made them.

Some of the history of Philips France can be found at https://en.wikipedia.org/wiki/Radiotechnique