[jcr1972]

Hello!

Well, I think it was about time to introduce myself properly and show a radio I got a few days ago.

First, I'm Jan, I live in Denmark (Europe), am 41 years old and am an eletronics technician. I never learned anything about tubes during my education, but tube radios/tv's has been on of my interests since I was just a small kid.
I joined this phorum because I actually have a few american radios too, one of them beeing the Philco 37-690. It is not restored yet, and as from what I read in this phorum, this is just the right place to be, when restoring a Philco. And other old radios too, of course.

The radio I am gonna show in this thread is a Bang & Olufsen from 1939. I am actually not a big fan of B&O products. More on the contrary. I think it is the same as with brand Z in the US. Not that they didn't produce some good sets too, but mostly it was just show off, and now everybody just thinks that because it is B&O it has to be high quality. Well, it's only high price...
A friend of mine who had a small B&O museum is giving up his collection. He is retired now and they are planning on moving to something smaller I think. I bought a few of their topmodels from him. One of them beeing this Master de Luxe 39 S:

[Image: http://i1080.photobucket.com/albums/j323...0S/sha.jpg]

It is a small floor console, having their top of the line chassis for that year. Different cabinets where available for this chassis, both tabletop and floor models.

[Image: http://i1080.photobucket.com/albums/j323...0S/shb.jpg]

[Image: http://i1080.photobucket.com/albums/j323...0S/shc.jpg]

It has 8 tubes including the tuning eye. 8 tubes may not sound like many, but several of them contains two systems, so it would be 11 if all tubes had one system only. It has a push-pull output, and the large transformer seen under the chassis is the output transformer. B&O's own by the way.

[Image: http://i1080.photobucket.com/albums/j323...0S/shd.jpg]

Underside of the chassis. I replaced a few caps only. No resistors were replaced and it still has some of the original tubes too. The filter cap was replaced by the former owner, and the set was fully working. I just replaced those few caps to make sure it would still remain safe to use. It has variable bandwith and it is seen in the top right corner. It is a couple of plates attached to the treble control, and they changes the coupling factor on the first IF transformer (the two coils between the plates).

[Image: http://i1080.photobucket.com/albums/j323...0S/she.jpg]

Here the chassis is back in the cabinet. To the left at the front, is the pushbutton section connected to the chassis through an octal plug.

[Image: http://i1080.photobucket.com/albums/j323...0S/shh.jpg]

Here is the 10" speaker. It is B&O's own production. They actually made very good speakers and they began to use permanent magnets very early. This one is very effective, and even though the output power of the radio only is maximum 7 Watts, it is capable of playing very loud and clear.

[Image: http://i1080.photobucket.com/albums/j323...0S/shi.jpg]

The beautiful dial and the push button section. B&O was very proud of this system. It was actually not very stable because they didn't use AFC, and the system had a tendency to drift from the station, and this just shows that B&O were not really good at building radios.

[Image: http://i1080.photobucket.com/albums/j323...0S/shj.jpg]

Well this was about it for now. I hope you all enjoyed watching this vintage danish product. I have some more to show for the future.

Jan - Denmark

[jontz]

Thanks for stopping by an introducing yourself and sharing your radio with us! It has some interesting features for sure. I love the large slide rule style dial, I've never seen one like that before.

You'll find everyone here is friendly and willing to share their knowledge. I know I've learned a lot just from hanging around. Don't be bashful about asking questions.

I look forward to following your 37-690 restoration! Take care and welcome to the phorum.

[exray]

Hi Jan,
Nice to see you here and that's a wonderful set you have. I'm the proud owner of a Master 38K. Interesting radio. Although it has been stored away for a few years I recently pulled it out again to clean and check it. Still working fine.

It uses a 104kc IF frequency and depends on a lot of front-end selectivity to prevent images. The RF coil deck looks very similar to yours. Its a good performer.

-Bill

   

[Arran]

That B & O reminds me of a post war British set like a Pye or a larger Bush. One trick I picked up from some fellow restorers, if you want to preserve the original looks under an all original chassis, is to dissemble the old paper capacitors by melting out the old innards and inserting new axial lead polyester film capacitors inside the old cardboard tubes. You can then seal up the ends with hot melt glue, preferably the brown kind. There were a few U.S sets that used variable IF bandwidth, American Bosch and Philco being two examples, perhaps a few others but it wasn't common. Bosch used a mechanical system to control the bandwidth, Philco used an electrical system.
I see that the B & O uses Phillips/Mullard style metal spray tubes, with a side contact base rather then pins, those were almost the industry standard in many parts of Europe during the late 1930s and 40s. Some Canadian Rogers built sets used a very similar idea, but the coating was thicker and it was usually grey or black, and the tubes used North American style bases such as octals.
Regards
Arran

[jcr1972]

Thanks for the nice replies!

I'm sure I will find this phorum very helpful, especially when I start on the Philco 37-690

@Bill,
It is interesting to see that a vintage danish radio found its way to the USA. I saw that particular Master 38K in the collection from where I bought my 39S. It is a beautiful radio! Mine has the more normal 440kHz IF frequency though.

@Arran,
Sometimes I do the trick you mention, by re-stuffing the old capacitors. In this case I couldn't do it, because those caps I replaced, had already been replaced once, probably in the 50's, with Jensen oilcaps. They become very unreliable with age, so I always replace them. Here we only have the white melt glue. I will be checking on the internet for the brown type, as it will be much easier to get a nice result than with the white one.
Variable bandwith was pretty common over here. Of course not on the cheaper sets, but most, if not all, the better ones had it. Both mechanical and electrical systems where used. On the older sets I think it was always mechanical. I never really got the point in having variable bandwith over here though, as no station at all had a wider bandwith than 9kHz. So a greater fidelity was never possible, but it might have been a good sales argument. I read that in the USA, especially in the 50's, several stations were transmitting with a much wider bandwith, allowing high fidelity receiving on AM. This was never the case over here. I use a sstran transmitter in my house and it uses a wide bandwith, making it possible to receive in a better guality on the sets with variable bandwith.
The side contact bases are calles P-type bases over here. As you mention they where very popular here in the late 30's. In the 40's both 2 and 3 different bases where used at the same time, and in the same radios too. Is the black coating on the canadian tubes a conductive coating too? Here the coating was either red, gold, silver or grey, and it is a conductive layer, making further shielding unnecessary.

Jan

[codefox1]

Don't ever let this one get away! From what I know nothing was spared to get outstanding results from these sets. I would still try a re-re-stuffing if at all possible, and there are tons of hints and methods here and elsewhere on the net on how to get this done.

Winters are kind of long there, YA? I'm a New yorker so I know how this goes.

[jcr1972]

Yeah, winters are VERY long here

And yes, this radio will be a keeper, that's for sure. From what I know it is even rare here. The problem with re-stuffing the caps in this particular one is, that they are not sealed with wax or tar in the ends where the leads goes out. The outside paper is folded in the ends (and then dipped in wax) and this makes it impossible to open them without destroying them. "Super Electric" and "Wicon" made their paper caps that way, until sometime in the early 50's.

Jan

[Arran]

The Rogers metal spray tubes had a thick coating covered with a layer of paint, the older ones were "S" series and colored grey, the newer ones with an octal base were "M" series. I don't know about the "S" series but the shielding was grounded through through pin #1 of the base on the "M" series tubes, just like a metal tube. The "S" series metal spray tubes were also used in the U.S by Grigsby Grunow "Majestic", although very briefly as they were introduced in 1931 and the company went bankrupt in 1933-34, in 1935 RCA introduced their metal octal line of tubes so the newly reincorporated "Majestic Radio and TV" switched to those.
I don't know who made the tubes for Grigsby Grunow but Rogers owned their own tube plant so they used the "M" series types in new radios until the 1942 model year. Whatever method they used to put it on there the coating would not peel off like the European types. Fortunately most will interchange with normal non metal spray tubes, like a 6K7M is the same as a 6K7, 6K7G, or 6K7GT. A 41M is the same as a 6K6G or 6K6GT.
Unfortunately because Rogers owned their own tube tube plant they also developed some special purpose types that have been out of production since the late 1950s at least. The most common of these were the 2X3 rectifiers, which was a half wave rectifier that was used in pairs. Another was a 20J8 mixer oscillator tube, those were used in a lot of sets around 1941-42. There were also the 6X6 magic eyes, those had a double shadow like some European types like the EM34, but those aren't necessary for the radio to work.
Regards
Arran

[jcr1972]

That was very interesting The coating on the european tubes had connection to one of the pins as well. But why the coating peeled off on some tubes I have no idea. I think it has something to do with how they where kept over the years. We had a danish tube factory in the 30's I think, and it was called Oxytron. I'm not sure if they made some of their own types too, or if they made direct replacements only, just giving them another type number such as Philips E443H is identical to Telefunken's RES964 and Valvo's L496D and so on. But I know Oxytrons where not quality tubes...

Jan

[Arran]

I don't know about how far back this goes but Phillips, Valvo, and Mullard were all divisions of Phillips at one time. Mullard was connected with Phillips going back to the middle 30s at least, after the war Phillips took them over outright. That's one of the points I find so amusing about the audiophools, they will pay top price for something like an ECC83/12AX7 just because it says "Mullard" on it but ignore identical tubes made in the Phillips plant in Holland, or the Valvo versions made in Germany. I don't think that the quality control would have varied that much between plants by the late 50s to to make one tube type made in Britain better then one made in Germany or Holland withing the same company.
Getting back to the metal spray coating on Rogers tube types, sometimes the black pain will peel off for whatever reason but I have never seen one where the shielding itself was coming off. Even on ones from farm battery sets from Alberta, that may have been stored in temperatures that were well below freezing. Whatever process Rogers came up with to make it bond worked.
Regards
Arran