Cossor radio, help request

[davidbm]

Hi all,

Yesterday during a general clean up of the back garden and shed, we finally dug out the Cossor radio my father grew up with. I've done a little research to try and find out more about the model itself but have come up somewhat short.

It appears to be very similar to the Cossor Melody Maker 494 internally, but more boxy on the outside, with a light bakelite fascia.

Unfortunately, the front is as good as it gets for the radio. Rust has taken its toll on the internals.

Out of morbid curiosity we plugged it in and unsurprisingly got very little in return, but thankfully no electric shocks or blue smoke either. The tubes noticeably warmed and when I turned the wavelength switch (SW/MW/LW) a little audible click developed on the speaker, but that was all.

My father, who is nearing the age of 60, grew up with this radio, he has great memories of listening to the Goon show + other BBC comedies, football games, the great boxing matches and so on - the world came to him via this radio.

I'd love to be able to bring this old machine back to life for him. Sanding & varnishing the wood panels, cleaning the brass speaker cover etc. are a given, but it would a shame to leave it dead inside.

I'm 25 and over the last few years I've developed a love of radio and for my sins have been known to wander round the shortwave bands at night in search of strange number stations and whatnot. Along the way I've learned some electronic theory and am planning to go for my Amateur license in the next few years.

So if any of you would be able to steer me towards firstly identifying this radio and then perhaps resources or general advice which you could offer regarding restoration of radios this old.

I have some time on my hands at the moment and would love the challenge

There were I think 5 tubes, although according to the 494 manual it's 4 + rectifier and my knowledge of tubes is zilch; here are the numbers from L to R:

Cossor 757, Cossor 787, Cossor 7C6, Cossor (no number i could read), Unreadable make 60-23

Thanks for any help and advice,
Dave

P.S. Almost as far back as my dad can remember, the frequency dial has been kaput, so for years he stuck his hand into the back and manually moved the vc around - getting his hand burned by the tubes more often than not. I guess he's lucky the transformer was on the other side

[paulsherwin]

Hi, and welcome.

You shouldn't have turned it on, but it's too late now. Fortunately you seem to have got away with it. Don't do it again though

I'm not a Cossor expert and don't recognise the radio, and it might be a special for the Irish market, but it will be reasonably easy to restore electrically. You will need to learn some valve electronics though. There's lots of stuff about valve radio restoration here.

To cut a long story short, you will need to change all the wax capacitors bigger than 0.001uF and replace any damaged or perished wiring. After that it's just a process of methodical fault finding until everything works.

You can do as much or as little restoration to the rusty chassis as you want, since it's largely cosmetic. Sanding the loose rust off, painting the rusty bits with Kurust, then repainting may be all that's needed, though you could do a lot more up to and including sandblasting. To do this you'd obviously need to strip out all the components, which will be a lot of work.

By the way, the term for those glass things that light up in Britain and Ireland is 'valves'. The Americans call them 'tubes'

Good luck, Paul

[davidbm]

Originally Posted by paulsherwin

By the way, the term for those glass things that light up in Britain and Ireland is 'valves'. The Americans call them 'tubes'

Good luck, Paul

Eeek!

Lesson learned, that's the last time I use that particular word here

Thanks for the advice

[PJL]

The layout is identical to the 494 chassis. You can purchase the service data by clicking on the top right. The rectifier is also a valve and should be a 7Y4 at the right of your picture behind the transformer.

It looks serviceable and complete, the rust can be cleaned off and I expect it will look OK from underneath. Lots of guidance and safety advice can be found on Paul's site http://www.vintage-radio.com/ who also hosts the forum.

BUT Don't plug it in again as you could cause irrepairable damage to the transformers until you have replaced some of the paper capacitor described on Paul's site.

[Boom]

Hi David. I've seen a lot worse than that. In fact it's not bad at all. You'll do it.

PS you do realise this set needs an aerial plugged into it? I mentioned that as you say there was a click when you operated the wavechange switch so it might possibly be working.

[Oldtimer74]

The electrolytic smoothing capacitors will need either 'reforming' ( search for this it has been on the forum many times and is not difficult) or replacing, before you ever connect it to the mains. Replacement valves are not too difficult to find if needed, try Crowthorne Tubes on Google.
The other item which may need some attention is the loudspeaker, which may have got rusty in the shed and need some carefull cleaning. Hopefully the mice have not got at the cone!!
As already indicated not a difficult job to get going unless it is very bad. Keep us informed.
Pat G3IKR

[Aerodyne]

These Cossor sets are not difficult to work on and work well once sorted. A couple of minor points to watch for: the valve pins are very thin and prone to corrosion. A good clean with fine abrasive paper should help - clean the holders too. The last part is more difficult but you may get away with a squirt or two of Servisol lubricating switch cleaner (which you will also need for the wavechange switch and the rotary controls).
Second point - the mains transformer is probably the type with snap connectors on the top as a means of selection of mains input voltages. The snap connector is often loose and is hard if not impossible to tighten securely enough to give a lasting repair. I tend to hard-solder the lead to the button.
-Tony

[Lee de Forest]

A good tip is to take photographs of everything and draw sketches before you replace a part making particular note of pin numbers. I also, as a novice, only replace one part at a time and if possible test after fitting each part.

[yestertech]

Hi David
Your set is similar to one which I once owned, the 517 AX which was an export model
see pic
Although they look similar, the 517 AX has the modern, 9 pin all glass valves
However, yours should be relatively simple to get going again and you may find all the valves are eminently serviceable !
The actual line up appears to be similar to the more general 494 /500/501 models :
7S7 7B7 7C6, 7C5, 7Y4
If you find any of these prove faulty, drop me a PM and I can let you have some good used examples for the cost of posting
I'm always cheered when a radio resurfaces with a connection to the original owner
I recently restored a 1930s HMV to be presented to someones elderly relative as a Xmas present. She had thought the radio was long gone ! Apparently it was quite a delightful 'reacquaintance' !

Andy

[davidbm]

Hi again all,

First I have to say thank you to everyone who has offered advice. I had to put the restoration project aside for a few weeks as a lot of other things had to be done first. But now I've got them out of the way, I have my shack set up for the restoration.

Today I took the chassis with all the components out of the box to have a first real look at the task ahead. Thankfully underneath, after being cleared of cobwebs and spider corpses looks in fairly good condition.

But there are one or two potential show stoppers to my very inexpert eye - I've attached a photo of a particularly sad looking capacitor and light fitting without a bulb.

If anyone could help identify the capacitor it would be a great help - I tried to gently remove the dirt but the colors are being removed with it, so I stopped.

The light fitting is to illuminate the Cossor logo on the front - I fear it may have fallen out when my grandmother dumped the radio in the bin all those years back

After my father had rescued it and taken it home and hoovered away all the ash (yes! ) we switched it on and it worked, but it has been in the shed for a long time since

[Steve_P]

It looks like the Irish version of the Cossor 500 chassis. You can get the data up top there.

Read, digest and learn: http://www.vintage-radio.com/repair-...ion/index.html

The valves may be OK, but other parts may not be. Always replace one cap - C25 on the Cossor sheet listed.

The dial bulb is 6.3v. 6 volts will do.

You'll get that working quite easily I am sure.

Cheers,

Steve P.

[davidbm]

I did a lot more research during the day and answered my own questions - I made the daft mistake of saying capacitors when i meant resistors in the post above

I apparently wasnt altogether awake. ..

Thanks again - making slow but steady progress with testing the various resistors, but I'm going to use this as the excuse to get a better multimeter and a variable power soldering iron

[Steve_P]

I notice. The main problem in a radio like this is capacitors though.

Good idea reference the multimeter and soldering iron.

Cheers,

Steve P.

[PaulR]

If it helps to encourage you, the second restoration I ever did was on a very similar set which my son found in a skip. It was also very rusty and took a bit of work as the valve holders weren't of the best quality and the connections had almost corroded away. I ended up replacing some of the valve holders which is a little fiddly but not too bad - yes they are still available!!

As Steve says I wouldnt worry too much about the values of the resistors, it is the capacitors that will need attention.

If you want to learn more about how valves and radios work Aerodyne, who has already contributed to this thread, has written some very informative books on the subject which are available from his web site.

Good luck, and keep up informed.

Paul

[YT2095UK]

if you`re stuck for a valve, I have a 7Y4 and a 7C6 here that I bought by mistake for my Cossor, mine uses diferent bases and so I have these spare.

[Phil G4SPZ]

Please do purchase the service data. Scroll back to the top of the page and simply click on the "Service Data by e-mail" button. As well as identifying all the components, their values and ratings, the service sheet should contain full instructions on re-stringing the dial cord. You will also find a description of operation of the various stages of the circuit, which may help your understanding of valve radios.

This is a good basic set on which to learn something about electronic repairs and also cabinet refurbishment. Hopefully the woodwork will be straightforward, but check carefully for the presence of woodworm and treat it if you find any flight holes. If the metal mesh grille doesn't respond to cleaning, these are easy to repaint using Plastikote antique gold paint, either brush-on or aerosol (other brands are available).

We all started in this hobby with a first radio, and hopefully if this one is successful you'll be encouraged to obtain and rescue other old sets! Well done on having the courage to tackle it. Please follow the safety guidance available on this website, though, check that the chassis is isolated or properly connected to mains earth, and if nothing else, use a plug-in RCD to power it up and give yourself some degree of protection from shock. If in doubt... please ask!