Waxy Capacitors - what did they look like when new?

[jamesinnewcastl]

Hi All

I'm restoring some Standard Beam Approach equipment to working condition so I am restuffing all the caps and the resistors too. My principle is to produce the same item that came out of the box 70 odd years ago. To do that I want the component values to be as accurate as possible to the original design, hence the restuffing.

But I'm looking at the waxy caps and wondering if the labels were actually that sad yellow colour when new or did they just get that way with age?

While I can re-use the original labels I also tried reprinting them, however the paper is bright white and doesn't get yellow when covered with yellow wax. Did they really print on yellow paper?

So does anyone know what colour the labels were when new? Any (colour) pics? Any pristine caps from back then? Anyone know what they used for the labels?

Cheers
James

[GMB]

I seem to remember that they looked much the same as now, only less sticky. Maybe slightly lighter in colour for those capacitors that got a bit baked in their life.

Having said that I am not old enough to have seen any new ones for sale. Just in equipment that was nothing like as old as it is now!

(Of course if you want totally authentic restoration then you should use my vacuum method of restoring capacitors back to working condition!)

[M0FYA Andy]

James,
I have some NOS 'waxies', packed six to a small cardboard box similar to a pack of playing cards, so they haven't been exposed to dust and grime, or heat.
They are 'Type AW 500 volts D.C. Tubular Paper Condensers', made by the British N.S.F. Co. Ltd., Keighley, Yorks., a company I have otherwise never heard of.

But in answer to your question, they are a buff colour, no different to a typical old one in colour, but devoid of dirt! Certainly not white, very much the colour of the old gummed paper tape.

I would have thought if as part of your restuffing process you warm the old cases with a heat-gun and wipe any dust off you won't be far wrong.

I'm intrigued by how you plan to restuff resistors, though...……….

Andy

[Dave1000]

https://www.gracesguide.co.uk/British_N._S._F._Co

[ekjdm14]

Originally Posted by M0FYA Andy

...I'm intrigued by how you plan to restuff resistors, though...

The consensus seems to be that the caps looked much the same just clean, and this tallies with some of the low-hour vintage equipment I've seen "Mr Carlson" open up on Youtube.

As for the resistor restuffing though, you have piqued my interest on this too, since surely a modern resistor small enough to fit inside the old shell would be of too low a power rating?

[G6Tanuki]

The 'standard' toggle-switches used in loads of post-WWII military gear were marked "NSF" and "CH" - the CH being "Cutler-Hammer", the original designer. See photo.

Waxies did not always exhibit the slimy yellowed countenance - there were loads of waxed-paper capacitors used in military/professional gear that had a metal case: TCC sold these as "Metalmite" and Dubilier had similar offerings. They're all now "replace-on-sight" leakfests.

[M0FYA Andy]

I confess that I always interpret the term 'waxies' to only mean capacitors with an outer case of waxed cardboard, not the metal-cased types which may well be wax-impregnated inside, and as you say, probably no more reliable with time.

Andy

[jamesinnewcastl]

Hi All

Thanks for the responses. It can only be that they printed on a yellow paper - perhaps simply to match the tube colour? But why choose that tobacco dinge?

I've already tried using tea to stain paper - OK but need stronger tea! Probably I'll go for clean, but yellow (like teeth!)

As for the resistors I haven't come up with a definitive plan yet. I know people have sealed new resistors in moulds taken from the original component, I was thinking of hexagonal hollow tufnol with the resistors wire wrapped around it.

Possibly drill out the original - slot the ends to drop the leads through some epoxy, then wrap. The conductive donor body may help heat dissipation.

As for the heat dissipation issue I've been checking out the actual in-circuit dissipation and for the vast majority it isn't much.

Cheers
James

[G6Tanuki]

Regarding the yellowness of the paper: a lot of paper/cardboard produced during WWII and the UK Stafford-Cripps immediate-postwar austerity era was of low-quality using lots of 'raw' wood-pulp rich in Lignin - which oxidizes as it ages, and turns yellow.

Book-paper generally used better-quality pulp that had less Lignin and was bleached so it stayed whiter - though if it's exposed to damp it can suffer localised discolouration which is known in the trade as 'foxing' - so you may come across antiquarian booksellers who describe a book as 'Slightly Foxed"!

I guess that in something that would rarely be seen when in-use it made economic sense to use cheap wood-pulp/card for waxie-cases.

[jamesinnewcastl]

Originally Posted by ekjdm14

The consensus seems to be that the caps looked much the same just clean, and this tallies with some of the low-hour vintage equipment I've seen "Mr Carlson" open up on Youtube.

Hi ekjdm14

I had a look at one of his videos and indeed there was a 1930 piece of kit that had wax caps. Even though they were American they were still the usual yellow but looked 'new'. I'll clean the tubes and try to match the resultant colour with the right colour paper.


Slightly off topic but I had measured all the resistors and they were all much higher than marked but I got a surprise when I measured a pot marked as 250K - it measured 460k! It's going to be hard sorting that one out - I may have to find a 100k pot and hope it has gone up in value!


Cheers
James

[M0FYA Andy]

James, I honestly think you're on a hiding to nothing regarding restuffing resistors! Some types may be more amenable than others, but, unlike a capacitor which has an outer case and stuff in the middle which can be removed, a carbon composition resistor is generally just a rod of brittle material with end-caps of some sort. The aim of making a piece of equipment look exactly like the day it was built in 1940 and be fully electrically compliant with its specification won't be easy. I'm like you, I don't like to compromise, but I suspect using more modern resistors, physically the right size and painted to look older, might be the way ahead. I've thought of using dog-bone resistors repainted to reflect the resistance they've drifted up to, but this only works if they are now stable at their new value!

[bluepilot]

Originally Posted by ekjdm14

As for the resistor restuffing though, you have piqued my interest on this too, since surely a modern resistor small enough to fit inside the old shell would be of too low a power rating?

Modern resistors are quite a bit smaller than old resistors of the same wattage rating. I can imagine it would be possible to fit a modern resistor inside an old one. However unlike capacitors, resistors get hot. I wonder if the casing of the old resistor would act like an insulator and stop the new resistor radiating properly. It might be significant if the resistor is used close to its wattage rating. Does anyone have any ideas?

[M0FYA Andy]

I think the hardest part of fitting a modern resistor inside an old one would be hollowing out a space in what is a brittle material, yet retaining structural integrity, and then connecting the leads of the new one whilst disconnecting any connection to what remains of the old one. All invisible to inspection, as that is the justification for the exercise.
I guess there are two main styles of physical/cosmetic appearance to deal with, dog-bones and simple cylinders. For the latter, finding a modern resistor of similar size and then repainting if deemed necessary may be the way. Dog-bones are harder to emulate in appearance. Maybe some experiments are needed to assess just how stable the value of old ones which have drifted high are. Do they continue drifting and how fast? Is the effect a function of whether the resistor is in use and getting hot?

Andy

[Refugee]

Those ceramic tube resistors might work with the carbon drilled out and a modern one shoved in with some computer processor heat-sink paste.

[David G4EBT]

Originally Posted by jamesinnewcastl

While I can re-use the original labels I also tried reprinting them, however the paper is bright white and doesn't get yellow when covered with yellow wax. Did they really print on yellow paper?

If you wanted to print new labels, you could make them any colour of the rainbow. Rather than try to get a shade of craft paper (which is generally only available in primary colours and few shades), just use a program such as Paint or Photoshop to create a 'shade card' of boxes that you've filled with various shades till you find one that's to your liking. In Paint, for example, if you chose a colour such as brown, yellow or whatever, then click on 'Edit Colours' you can make the colour lighter darker - any hue that you want. I've quickly knocked up an example in pic 1.

The colours may look a little different when printed off than when on the screen. When you've created a shade that you think looks acceptable, you can then create a label to roll around the cap, by adding wording in a suitable font as close to the original as possible.

Pic 2 is of a cap label I created based on an old label that was too far gone. Pic 3 is of a 'Service Replacement' paper boxed cap fitted to a 1935 Ekco in the early 40s. I made a new box from PCB laminate, and rather create a new label from scratch, to make it look more authentic, I took a photo of the old crumpled box, and cleaned up the image in photoshop and printed it off as shown in 4, so when finished, the cap would still look old and more authentic.

I did the same with the lettering on the top of the capacitor block: Took a photo, then cleaned up the image in Photoshop as shown in pic 5, which I printed off to apply to the new box.

Ten years ago now, forum member Colin Wood ('Retired') set up quite an assembly line to make authentic looking caps which found they way into may radios back then.

https://www.vintage-radio.net/forum/...ad.php?t=46963

You're on a hiding to nothing trying to create resistors. Early carbon rod ones can't easily be drilled out, though ceramic tube ones can be with difficulty, but you'll only get a .6 Watt resistor inside. I've tried it, out of curiosity, and by the time I'd finished, through handling the resistor, most of the coloured bands had rubbed off.

You can mould various modelling materials around a modern resistor, adding 'wire loop' terminations then paint it to look like old body/tip/dot carbon rod resistors and some restorers have. However, in my view, it makes more sense replacing them with modern 1 Watt and 2 Watt metal film resistors which are a similar size to 1/2 Watt and 1 Watt old resistors and don't look out of place.

Hope that might help a bit.

Good luck in your endeavours.

[jamesinnewcastl]

Hi All

Resistors must get hot - that is how they work, that is literally all they do.

Yes, trapping heat can spell disaster - I'm told that you can melt tungsten wire (m.p. = 3,422 degrees C) with a 9V battery and a glass of water. The steam jacket around the hot wire stops heat leaving the system and the only thing physics can do in that event is to raise the temperature and keep on raising it.

I have colleagures at work that can't work out why the 30W Monitor they have designed is overheating or why a 'heat-sink' isn't 'sucking' heat out! Yet they understand ohms law and the power equation.

Materials don't usually have enormous thermal resistances and if you don't set out to dissipate massive amounts of heat then you may find that the temperatures at various interfaces are acceptable. Most of the resistors are dissipating about 10mW - it's possible that the leads themselves might be enough to drain that amount of heat away.

But, I've not yet tried any of this so it could still be impractical. I would try to put resistors in series if possible to spread the heat profile for the bigger resistances. I may have to get the trusty Dremel out tonight and give it a bash in the true spirit of Garden Shed man. I'll let you know. It may not take long, I don't actually have many of those resistors...

Cheers
James

[jamesinnewcastl]

Hi David

Our posts crossed - I have just been to Hobby Craft to gasp at the price of coloured paper, only to gasp again reading your post in which you point out what should have been blindingly obvious which is to print the right colour for myself!

I've scanned the original label and then overlaid it with new text and colored bands on one layer - so I'll just add a background layer in pub ceiling tobacco.

I've just this week bought a brand new printer which has buckets for the ink instead of cartridges so I can happily play to my hearts content. I'll put up my efforts later.

Cheers
James

[M0FYA Andy]

James,
I'm wondering why you need to make labels, does this mean that instead of restuffing the original capacitors you're fabricating new replica cases?
Andy

[jamesinnewcastl]

Originally Posted by M0FYA Andy

I'm wondering why you need to make labels, does this mean that instead of restuffing the original capacitors you're fabricating new replica cases?

Hi Andy

I'm only keeping the case and the graphics now. I've just realised that all I need to do is to print a new cover for the case, print a new label and stuff a new capacitance in!

I had a look at the resistors too. Happily one of the tiny dog bones is only a few percent out so that can stay as is. The biggest one I can make out of a plastic tube. The small ones are tiny but there is always surface mount!!! Stuck close next to each other on a long thin insulator - soldered to connect them - a work in progress!


Cheers
James

[M0FYA Andy]

Be aware of the voltage rating of surface-mount and other modern tiddlers!

Andy