Hi

I've just bought a Cossor Melody Maker, of about 1927-28. A kit radio imported from Britain, one of these:

http://www.radiomuseum.org/r/cossor_melody_maker.html.

Its almost complete but very dusty and dirty - obviously been stored in a shed or barn. It even has an Australian Diamond brand C battery in it. I have experience with valve gear from the 50's onwards but I've never worked on anything this old. So I have some questions, well, quite a few actually!

The detector valve, Cossor 210RC, has a loose base. The wires still appear connected. What should I use to glue it back together? Theres a convenient hole in the base where the old glue fell out from. Would hot glue work? I doubt the valve gets that hot, not with 2 volts at 100mA for the filament. The hole isn't that big and I'd have trouble getting epoxy to flow down it.

The AF valve, a 220P, has an open filament. Wheres a good place to get these, or an equivalent (eg Mullard PM2)? I have found one on ebay in the UK. EVATCO don't list anything that early. Are there any other Australian suppliers?

The case is a steel box assembled with angle pieces held by nuts and bolts. It is covered in surface rust. It would appear to have had a crackle or similar finish in black. Is it reasonable to clean this off and repaint or should I try to leave it more or less as it is? It doesn't seem to be a very rare radio, there were over 350,000 made. I'm tempted to repaint it, especially as the rest of the front panel fittings will clean up well. I'm only missing the knob on the LT pull on switch.

I'll build an external power supply for it and for the meantime I can use a 'modern' output transformer and speaker but I'd like to get a horn speaker to suit. What should I look for and where should I look? I've not found any mention of Cossor supplying speakers. Were there any Australian manufacturers from this period? And am I likely to find one (without mortgaging the house!)?

Sorry, the post has got a little long! Many thanks for any help.
Murray

There is a post on the US forum re using a water based "Elmer's glue on a valve base. He cooked the transformer.

Araldite is the best, and I have actually used it on a rectifier. Just wipe a trail around the interface between base & glass & wrap some insulation tape around the thing to stop the stuff running during reaction.

I did have a PM2 pass under my nose recently: I am looking for a socket for the European 4 pins as it is different than UX4 which my ancient tester has.

I would, albeit that it is just a triode, like to see the specs of 220P (Franks Electron tube pages) as it may not have the same filament volts. Many Philips were 4V.

You just cannot bung anything in the hole because it fits.

Marc

I have always used superglue to reattach valve bases if loose. Quick and easy. Valves treated twenty years ago are still working OK.

As I never take valves out by grabbing the envelope some of these might not be very firmly attached, but they are not loose. And this is probably enough to prevent the wires inside the base from breaking.

Usually take out bakelite based valves by levering out gently with a small screwdriver until loose in the socket.

If the chassis is out & their are shields. octal's can be pushed by a dowel on the spigot.

Marc

Thanks for the replies. I'd not thought of using epoxy from the outside to glue the valve base. Seems pretty obvious now!

The PM2 seems a reasonable equivalent to the Cossor valve and certainly more obtainable. I'm guessing these simple radios are not too fussed about some variation.

I'm still considering what to do with the case. Its just rough enough that I think a repaint is justified but I'm still hesitant.

Cheers
Murray

I'm still considering what to do with the case. Its just rough enough that I think a repaint is justified but I'm still hesitant.

Some will say don't repaint as it will devalue it.

However, going by what I've seen at HRSA auctions, I wouldn't say there's a very big market for "coffin" radios apart from a few highly sought after models.

If the case is pretty rough, I would be inclined to repaint it, providing:
The case is either sand blasted or rubbed down to get a perfectly smooth surface,
You can match the colour and texture of the original,
You pull the case apart and paint each component seperately, to avoid paint build up where panels and corners overlap.

I painted this RCA speaker with a bronze hammertone finish, as the original was badly chipped and had quite a bit of rust. The original patina was just not worth looking at.

Harold

A follow up on what I did with this radio.

On the advice of someone I met who restored vintage guitars I treated the rust with one of those phosphoric acid 'neutralisers' and then applied a very very light spray coat of paint. The paint is matte black and with just a hint of coverage the original wrinkle finish shows through quite well. I'm very pleased with the result.

I built a power supply and found the detector valve wouldn't oscillate. On a whim I tried the AF PA valve in its place and it worked quite well - whats an audio valve doing oscillating at RF frequencies? I have a replacement detector coming from England.

Murray