Capacitor selection

[Bushbaby]

My mistake then...they must be ceramics.

[Bushbaby]

How did I get this so wrong!!

[Amie]

Hi Bush...

Shouldn't worry, I was confused a short while ago by an open circuit Erie resistor that turned out to be a capacitor that they used to house in the same type of ceramic tube as their infamous Norfolk resistors...

[Mark Hennessy]

There's so much variety in electronic components, and even very experienced people can get caught out occasionally. For example, film resistors have the "dogbone shape" because of the metal end caps:

https://res.cloudinary.com/rsc/image/upl...0-01?pgw=1&pgwact=1

But I remember being initially confused by these:

https://i.pinimg.com/originals/e1/67/4e/...1dfebc.jpg

Which are carbon film, but don't have the bulges at the end. If you hold them at the right angle, you'll be able to see the spiral cut into the film. I bought a large box of these from an auction at uni about 30 years ago and almost forgot about them, but now I use them as a period-appropriate replacement for carbon-comp resistor in transistor radios.

Have a look at the resistors on this board: http://3.bp.blogspot.com/-RmX0J5gCH7Q/Ta...mp-top.jpg

I can't immediately remember the name for them - if I could, I'd perhaps be able to find a better image - but I remember being very confused when I first saw these in an old car radio. In my defence, I was only 9 or 10! The PCB didn't have a silk-screen - unlike the Hacker Hunter shown in that image - but there wasn't anything else they could be, so I deduced that they had to be resistors. I didn't have a multimeter by this point.

The Erie caps Amie mentions are also fun. She might have been referring to a different type, but the ones I immediately think of are the ones with pre-formed legs. The body colour was a strong clue for me - I was already familiar with the colours used for the resistors, and some of the caps had the value printed rather than colour coded:

https://www.vintage-radio.net/forum/atta...ntid=74303&d=1356354571

Another variation is shown in the Hacker Hunter image above - in red, just above R7 and R9.

As for the resistors, I recycled a lot of those when I was a kid. I can't explain why, but I really liked the way they looked.

https://www.vintage-radio.net/forum/atta...ntid=74199&d=1356114833

The light beige ones were the most common, and were 10% carbon comp, but there were some in shades of green that were also carbon-comp (sometimes 20%). But note the green one furthest from the camera, just in front of the larger 33k. Although it's not really possible to see from the photo, that one is actually a carbon film. In the flesh, you can see the spiral through the paint. I had loads of these in a broken Metrosound amplifier and re-used lots of them in projects - Hacker used them in the Sovereign III and related sets. They're nice. One problem that can affect all of these resistors and caps with the pre-formed legs/end caps: the caps can break. It's often an invisible - or near-invisible - crack in the metal that causes all sorts of random stuff.

(Picture credit - the last two came from "Dazzlevision" on UKVRRR: https://www.vintage-radio.net/forum/show...hp?t=91511)

When it comes to component identification, and especially with capacitors, a picture says a thousand words

[Bushbaby]

Comments much appreciated. 
I should have realised that these were 'budget' made equipment and wouldn't have used expensive components. Perhaps its because I dont use ceramic caps that much (if at all) that I didn't spot thats what these were. I looked up Lemco caps and instantly thought these were silver micas albeit that in agreement with Jeffreys comments about them being square/rectangular in shape this is what I found when I had a look at my old RS 'S' Mica caps so I did feel highly confused. They also seemed to be far too big as well.

This is why I like this forum - you will get good answers to questions asked. Again, thanks for your valuable replies.


   

[ppppenguin]

An excellent example of why a picture is often worth a thousand words.

[Kalee20]

Disc ceramic!

May have been budget equipment, but good-quality Mullard C426 capacitor visible there, and Iskra UPM carbon-film resistors, which have a good record for stability and reliability.

[Bushbaby]

you are spot on Jeffrey - I should have posted a picture......lesson learned.

[ppppenguin]

..... but good-quality Mullard C426 capacitor visible ......

I think you mean C296, often known as "mustard" after their colour. At the time that was built they were commonplace and low cost.

Other common Mullard caps were C280 "tropical fish" and C281, sometimes called "chiclet".

[Bushbaby]

I believe I have been lucky over the last few years as I have collected a lot of NOS 'mustard' caps and never really know when they suitable to be used?