What changes in 80 years of manufacture

[Cobaltblue]

I was lucky enough to be given two folders of information related to Cossor Manufacture in the 1940's at the recent RWB meet.

Many of you will know Chris, Barker Fan and keen on 30's Grams.

All around good guy.

Chris handed me the folders a RWB.

Today was the first chance to have even a cursory glance.

It's just like my day job

Amongst other things I work in product development.

Here were the documents that allowed Cossor to produce product, BOM's individual drawings manufacturing drawings and detailed drawings for 3rd party manufacture.

I will need to go through it all but there is almost enough detail to manufacture some items from scratch.

In my heart I know all the manufactures must have done it this way but see the actual drawings it breaks my heart no know how much has been lost.

Now I need to work out how best to preserve this resouce and make it available.

A3 scaning is easy A0 not so much

As ever looking for anything Cossor I don't have.

Cheers

Mike T

[crackle]

I feel it is important to preserve as much of this radio heritage as possible. Not to just buy and collect radios and squirrel them away never to be seen and marvelled at by others.

It would be great if more people were as conscious of cataloguing and presenting the information they have available for all to see, as yourself and a few others.

Well done, I am sure you will work out what to do with it all.

Mike

[Cobaltblue]

Thanks Mike.

I never expected to see this sort of documentation.

Cheers

Mike T

[mark2collection]

This is why I enjoy working with vintage technology, especially radio.

Social history, that and when I'm working on a set, I always imagine what it must have been like pre-production in the drawing office, the machine shops pressing chassis's & fashioning the brackets/sub-assemblies, the coil winders & all the people on the factory floor assembling the rest of the set, testing, then off to dispatch, plus the people who designed the instruction booklet, box and packaging.

Then of course, the first proud owner, walking out of the shop to bring a wealth of news and entertainment back home for the whole family to enjoy.

Soppy perhaps, and as you say, heart breaking how much of this information has gone forever.

I'm doing all I can in sympathetically preserve my sets for the next generation to enjoy as much as I have, any documents have been passed to those who are better placed than myself to secure their future.

Mark
PS, would love some in-depth info on a Cossor 501AC, especially technical drawings or, a BoM. It would be seriously interesting to look through. My set, she's the 3rd in-line for an overhaul.

[Cobaltblue]

let you know

Cheers

Mike T

[Graham G3ZVT]

Originally Posted by Cobaltblue

Now I need to work out how best to preserve this resouce and make it available.

A3 scaning is easy A0 not so much

DSLR + stepladder can achieve remarkable results.

[Restoration73]

I have these original Cossor TV service manuals (pre-Philips era) that may be of interest;

Models 937, 938, 938F, 939, 939F
Model 944, Model 946, Model 947, Model 948

PM welcome

[crackle]

Originally Posted by rambo1152

DSLR + stepladder can achieve remarkable results.

Good idea, it is not so important that the image may be slightly distorted at the edges. Recording and presenting the information for all to see is the aim of the game.
I wish I had done that on some of the original "blue prints" I scanned from the KB information I acquired, rather than scanning the document on an A4 scanner and manually stitching the 9 or 12 images together.

If anybody has any unique KB documents I am happy to "borrow" them, scan and return them, and present them on my KB Museum website.

Mike

[Herald1360]

Originally Posted by rambo1152

DSLR + stepladder can achieve remarkable results.

DSLR + tripod and a suitable wall could be easier / safer!

[Cobaltblue]

Originally Posted by Restoration73

I have these original Cossor TV service manuals (pre-Philips era) that may be of interest;

Models 937, 938, 938F, 939, 939F
Model 944, Model 946, Model 947, Model 948

PM welcome

Hi Restoration

Thats a very kind offer but I already have examples of these TV service manuals.

I am still searching for pre war Service sheets numbered SM1 and SM7 however. Unfortunately I don't know which models they covered or even if they were ever published at all.

Thanks for the ideas concerning scanning these documents.

looks as if a DSLR is the way to go.

Cheers

Mike T

[Cobaltblue]

I grabbed a couple this morning to copy on the scanner these are from the early 1950's

One is an IF coil the other is a TV frame output transformer.

Cheers

Mike T

[kalee20]

In fact, neither of these is completed!

The IFT doesn't list the turns, the distance apart of the coils, or the wire gauge. It does give inductances, but no measure of coupling between coils. This is critical in an IFT.

Interesting that the test frequency is 1MHz! To be honest, the inductances look a bit small for an AM IFT, though it could be for transistor circuits (with correspondingly larger parallel capacitor), but why not test at the operating frequency, likely to be 470kHz? Surely LCR bridges at the time could accommodate that?

The frame output transformer has no test info.

I tried to see if the drawing border indicated that there are more sheets to the whole drawing, but couldn't see anything!

[Cobaltblue]

They are not in any kind of order but it does seem to call up other drawings and I don't have complete sets as far as I know.

The way the drawings are done is curious I would have expected all the details to be on a single drawing but that doesn't seem to be the case.

Cheers

Mike T

[Refugee]

It sounds like those drawings are details that would have been sent to outside contractors to make things like insulators and metal frames so they would only have the information that the contractor would need and nothing else that might make them difficult to read.

[evingar]

Originally Posted by Cobaltblue

They are not in any kind of order but it does seem to call up other drawings and I don't have complete sets as far as I know.

The way the drawings are done is curious I would have expected all the details to be on a single drawing but that doesn't seem to be the case.

Cheers

Mike T

It may be done that way so that the same drawing can be used for several assemblies of a similar type. Details of the various options being called up elsewhere.


A company I used to work for did that and items were built using drawing "structures".

[Cobaltblue]

Originally Posted by kalee20

In fact, neither of these is completed!

The IFT doesn't list the turns, the distance apart of the coils, or the wire gauge. It does give inductances, but no measure of coupling between coils. This is critical in an IFT.

Having had some time this evening I looked through one pack.

I think evingar may be on to something.

There are a series of drawings.

The first seems to be details of the bare former,

The second the windings distances turns etc.

The third the assembly of the complete coil minus the can.

These look like TV IF coils rather than Radio.

Cheers

Mike T

[crackle]

From original documents I have from KB it is obvious that they often used an existing document, and altered it to "fit" a new model, this could help explain some of the errors seen on KB documents.

Mike

[boxdoctor]

It seems odd that they quote the inductance of the coil at a certain specified frequency, as the inductance will be constant regardless of frequency.
Looks like a very interesting find indeed, Mike T.

[Cobaltblue]

Although the inductance won't change with frequency it's impedence will.

Simple measuring equipment doesn't resolve the components into L, R and C

So the percieved inductance with simple measurement will change with frequency.

Many modern LCR meters have selectable measuring frequency for this reason

Cheers

Mike T

[kalee20]

Originally Posted by boxdoctor

It seems odd that they quote the inductance of the coil at a certain specified frequency, as the inductance will be constant regardless of frequency.

Ideally, yes - in practice, no!

A 10H choke, for instance, is going to have significant parallel capacitance. So whereas it may measure 10H on a modern, hi-spec LCR analyser, it is likely to measure rather higher at higher frequencies (up to its self-resonant frequency) and then show a negative figure at frequencies above SRF. Which could be as low as 5kHz.

A 10uH inductor, on the other hand, will be so dominated by its DC resistance at low frequencies, that although measuring at 100Hz may show a credible inductance measurement, the instrument will have such a hard job extracting a few microvolts of quadrature signal in the presence of millivolts of in-phase signal, that the result will be uncertain. I've seen readouts fluctuate from 8 - 12uH for such components, on successive readout updates, when measuring at an unsuitable frequency.

The best solution is to measure as near as possible under the conditions of use. For a wideband choke, the highest frequency of interest is the one to go for, for the ultra-cautious a second measurement at the lowest frequency would guard against the unlikely, but possible, scenario whereby someone has used the wrong core (giving low inductance) but also wound badly such that self-capacitance is high (which might just give a satisfactory 'inductance' reading at a single, spot frequency).

Wind the clock back 60 years and LCR analysers didn't exist. Inductances were measured with a bridge; and the better bridges had the facility to assess series resistance as well. But the same arguments apply.