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Old 14th May 2018, 8:05 pm   #1
Boater Sam
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Default Cossor old confusion.

Latest plaything off the pile of non working radios is a Cossor 360, battery TRF Super- Ferrodyne, 3 valves.

A beautiful art deco cabinet, any idea what year?
Mine has no back but has the metal brackets for one, I know many battery sets were backless but not this one.
There is oodles of battery and accumulator space. The pull out divider and shelf are present. It came with an Atlas K12/18 eliminator which is working with new semiconductor rectifiers fitted.

There seems to be little information on this set, I have the Cossor sheet S.M.27 but its a bit sketchy.

For instance, what rating/voltage is the fuse bulb on the rear chassis rail? Mine has none.

The 'speaker is a low impedance moving coil with the transformer mounted on the frame, 10K ohm primary is marked. But according to the sheet it should be a high impedance moving iron. Yet it looks like the original, it fits the baffle and is hollow rivetted to it with a muslin bag which has rotted. There are another set of unused holes for mounting a larger 'speaker but the circular cut out is the right size for the cone.

There is a rogue 10k HT resistor that will be changed for a period dog bone, the three 0,1uf Cosser cardboard caps have morphed into resistors. They are tar ended so I will cook them out and use the printed sleeves to hide new parts, reclaiming a bit of tar to dress the ends.
Other than this resistor it looks untouched.
The wiring to the batteries is well beyond re-use and will have to be replaced, LT, HT and two Grid Bias batteries. All the labels are present.

Has anyone got another?
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Old 14th May 2018, 8:18 pm   #2
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Default Re: Cossor old confusion.

Hi Sam

Its a 1936 model first released in 1935

Are you sure its not a 363?

The fuse bulb is 3.5V 0.15A

Yes I have one of course.

Pretty certain mine has a 2/3rds back let you know if I can find it

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Last edited by Cobaltblue; 14th May 2018 at 8:22 pm. Reason: saw 370 instead of 360
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Old 14th May 2018, 9:02 pm   #3
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Default Re: Cossor old confusion.

Excellent Mike, thanks again, knew you would respond.

Another user of the ever rarer 3.5v 0.15a bulbs, lucky I have some.

The back only covers the chassis compartment, the battery shelf and the side box for the accumulator are not covered.

Now it was sold to me as a 360 but you are quite right, its a 363, once again the master has spoken, thank you.

I searched everywhere for a set that looked like this one and was convinced it was 360, never found another with the same cabinet, but knowing Cossor's habit of using the same woodwork for multiple sets it makes perfect sense.
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Old 15th May 2018, 9:05 am   #4
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Default Re: Cossor old confusion.

Can you post a picture? I may have TWO of these, which I'm unlikely to do anything with.
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Old 15th May 2018, 9:25 am   #5
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Default Re: Cossor old confusion.

Quote:
Originally Posted by Boater Sam View Post

I searched everywhere for a set that looked like this one and was convinced it was 360, never found another with the same cabinet, but knowing Cossor's habit of using the same woodwork for multiple sets it makes perfect sense.
Sam.
Although not complete yet if your trying to identify Cossor sets could do worse than starting here.

http://www.cossor.co.uk/rogues-gallary

Cheers

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Old 15th May 2018, 9:27 am   #6
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Default Re: Cossor old confusion.

I'm out today but will take a picture.
Had a look on Radiomuseum for a picture and now I am really confused. There is no entry for a 360, but the 363 pictures are nothing like my set or the picture on Cossor's service sheet for the 363.
Could they have a wrong entry?
Mike ( Cobaltblue ) is the authority on Cossor and he agrees with me that the 360 and 363 share the identical cabinets.
Could you post a straight on shot of the back panel Brigham please so that I can copy it?
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Old 15th May 2018, 9:31 am   #7
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Default Re: Cossor old confusion.

Ah, thanks Mike.
It would appear that the Radiomuseum have a 373 or 378 or 379 or 437B erroniously entered as a 363.
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Old 15th May 2018, 9:33 am   #8
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Default Re: Cossor old confusion.

So Sam has already worked this out I am too slow!!

I think the picture of 363 in the Radiomuseum is a 373 or there are two more battery sets in that cabinet.

Its much easier to see if you follow my Rogues link.

Cheers

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Last edited by Cobaltblue; 15th May 2018 at 9:34 am. Reason: Crossed with Sam
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Old 15th May 2018, 8:13 pm   #9
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Default Re: Cossor old confusion.

Question now is whether to tell the Radiomuseum or not? Am I definitely correct in my deduction?
It's a Howard Craven upload and he is seldom wrong, don't want to upset anyone - again.

Had a couple of hours today restuffing another four 0.1uf paper caps, melting out the tar ends is messy but they look original when done.

Discovered that the output coupling transformer is open circuit on all windings so it's an unwind and count the turns job. The core is "E" lams laid alternately without "I"s and show green corrosion so it's probably the dreaded green spot corrosion that has caused its demise.
The wire is 0.08mm diameter including the enamel insulation, what size will it be?

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Old 15th May 2018, 8:36 pm   #10
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Default Re: Cossor old confusion.

Hi Sam, wire is possibly 0.061mm, or 46 SWG in old money.

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Old 16th May 2018, 9:06 am   #11
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Default Re: Cossor old confusion.

Thanks Ed, by consulting wire tables I guessed at 45swg but of course we only use the even numbers.
It's more labourious unwinding than rewinding I find, no counter on the unwind. I had thought of using a calculator in constant mode with a switch to the = button but the wire's too thin to take any strain.
Maybe a photocell switch? Any ideas?
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Old 16th May 2018, 4:54 pm   #12
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Default Re: Cossor old confusion.

Mine look like the 360 or 363 on the 'rogues gallery'.
Neither has a back.
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Old 16th May 2018, 5:38 pm   #13
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Default Re: Cossor old confusion.

Pretty much the only difference is the output valve and a moving coil speaker versus a reed speaker (and their asociated components).

So the way to tell is which speaker is fitted.

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Old 16th May 2018, 6:48 pm   #14
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Default Re: Cossor old confusion.

An arduous and frustrating day, unwinding and counting the turns on the intervalve transformer bobin, all 13000 of them!
The 46 swg wire is just too fragile to put the bobin on the winder and pull it off so it had to be done manually.
Not surprised that it was open circuit, green spot corrosion at both ends of the bobin core, multiple breaks as it unwound, and it was wound very tightly against the end cheeks.
If anyone wants to know, the tap is at turn 4440, it's an auto transformer.
Not much progress to show really for a whole day, fortunately it's not a paying job. New wire on order, it will go on easier and faster than it came off.
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Old 16th May 2018, 6:53 pm   #15
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Default Re: Cossor old confusion.

You gotta love Cossor for hanging on to 20's technology so long.......

Or maybe not

Cheers

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Old 16th May 2018, 6:55 pm   #16
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Default Re: Cossor old confusion.

Quote:
Originally Posted by Boater Sam View Post
If anyone wants to know, the tap is at turn 4440, its an auto transformer.
Thanks Sam

That is useful information so far I have never rewound one although I have several OC

Cheers

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Old 16th May 2018, 8:23 pm   #17
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Default Re: Cossor old confusion.

That's turn 4440 from the outside as I counted them off, so 8560 from the start. Go on, get rewinding!
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Old 16th May 2018, 8:24 pm   #18
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Default Re: Cossor old confusion.

Hi Sam, some winders are fitted with reversible counters!
It looks like a 3:1 unit, possibly the most usual ratio.
When rewinding use grade 2 wire (double insulated) and no interleaving paper, making the job easier. As it is an auto transformer no paper is required between pri and sec either.

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Old 17th May 2018, 7:12 am   #19
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Default Re: Cossor old confusion.

I love old Cossors. They were able to make beautiful looking sets at prices that were reachable by the average man. My 375 (photo left) is my favourite set of all time and is a sister model to the 360. I also have the 364 'thermometer ' set that is equally handsome.
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Old 18th May 2018, 8:58 pm   #20
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Default Re: Cossor old confusion.

Found another paper capacitor, top cut 0.005uf across the output transformer. It's only in the 363 of course being the one with a low impedance speaker.
It's a very thin tube and finding a capacitor to fit inside is not easy so I used four very small 250v 0.047uf in series parallel. Should be enough voltage in reserve, the original is 450v.
Replacing the rotted rubber cables is straight forward. Having no silicone cables I decided to cheat and use PVC despite its appearance.
A couple of resistors have gone high. I decided to shunt them rather than try to find good dog bones. The tiny shunts are hidden behind the originals.
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