SPRAY-SHIELD TUBES

[Bob Masse]

That was sure an interesting read on the Grigsby-Grunow company. They sure flew high. Must of got to close to the sun. It seems that type of story occurred, with many products, since the beginning of the industrial revolution. A new product comes out. Then it starts to sell quite well. Then, there are many technical improvements made to it. It is well made and designed to last many years. Soon everybody wants one. Companies can’t keep up with demand. A downturn in the economy occurs. The market is saturated with the product. Since it will last ten to twenty years, there is no need to buy a new one. The market stagnates.

The Midwest radios looked like they were well built. They must of done quite well selling tubes. That 24 tube Royale Victoria model caught my eye.
Bob

• This reply was modified 3 years, 2 months ago by Bob Masse.

[Dan Walker]

Eric S. Where would you buy that hydrofloric acid? Is that the real name?
Dan in calgary

[Eric Strasen]

Dan,
The product is Etchall. It is not dilute hydrofluoric acid as I earlier thought, but ammonium bifluoride. In any event, the user is supposed to wear latex or rubber gloves, safety goggles and “protective clothing” (almost sounds like they want you to put on a haz-mat suit).
I didn’t go beyond the latex gloves.
It comes in several different formats. I chose the liquid as I used it for frosting pilot lamps. Just pour it in a small plastic tub — a tub meant for denture cleaning/storage works great, as long as you don’t plan on parking your teeth in it — and put your pilot lamps in it for 15 minutes. It does not affect the metal base of the lamp, just the glass.
Etchall also comes in a cream, which is what you would want to frost the glass on a vacuum tube.
It is available direct from the manufacturer — https://www.etchall.com — and from eBay. Price appears to be the same either way.
The liquid comes in a 4-ounce bottle. I didn’t search the site long enough to determine if it is available in larger sizes.
The stuff may be used repeated times.
Hope this was helpful.
Eric S.

[Eric Strasen]

Dan (continued),
From the looks of their website, it doesn’t appear Etchall had pilot lamps or vacuum tubes in mind when marketing their product.
They are trying to sell it to the artsy glass crowd, so if you have a glass store which caters to DIY glass artists in Calgary, it may be available locally.
Eric S.

[Ken Au]

Hello Bob and Eric,
I have bought this exact radio, 1933-34 Rogers 403/903 Chassis R371 radio from last month’s CVRS swap meet in Burnaby.I was able to test 2 of the 3 tubes inside and had good readings.
I can’t find the settings to test the 6G7S with my Knight 600B tester, so I will go ahead to do restoration assuming that it is still good. Upon checking the schematic, I am confused about the pin connections of the 6G7S. For a 7 pin tube, It is a rule that pin 1 and 7, which are the bigger diameter pins are the heaters. But in the schematic, Pin 7 is one of the two plates of the full wave rectifier ? I can’t find any information on the internet about this tube. A diagram of the tube would be helpful. Your help is very much appreciated.
Ken

[Don Henschel]

As for Rogers I would say perhaps he wasn’t the only “usual suspect” as most of my European tubes or should I say valves are spray coated as well and many date back to the early 30’s. Some are ballon style and the rest are shoulder top. These “valves” are also the CT8 style.

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[Don Henschel]

Now if they had the Third Reich ink stamp on them they would be worth a lot more! I get Blitzkrieged on those. This radio Volksempfanger (People’s Radio) or Sieg Heil Radio as I call it is a Braun VE301Wn from 1933 and as you can see it also has the Spray Shield “Valve” perched below the reed style Lautsprecher so it would be safe to say pretty much everybody back then used them. I also find the emblem above the dial quite amuzing to say the least and it is the same as the promo poster showing the Eagle, probably Hitler with the circles being the radio waves as he poisons the radio waves LOL

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[Eric Strasen]

American Bosch, AKA United American Bosch and American Bosch Magneto Corporation, marketed an entry level AA-5 set in the late 1930’s, apparently aimed at Nazis belonging to the German-American Bund, with swastikas on the radio’s two knobs. These knobs disappeared after Germany declared war on the US. But forgive and forget, I guess, because a few collectors are looking for them now. Good luck finding any!
As far as spray-shield tubes go, Grigsby-Grunow marketed them in pre-octal days and used them in their “Smart Set” Majestic radios of the early 1930’s. There are still a lot of these floating around, most of which are losing their coating and darn near all are microphonic as all get out (from my sad experience).

[Don Henschel]

Fritz Kuhn would be proud! Never seen one of those AA-5 with these knobs but the DKE38 (Kleinempfanger) or the VE301DYN clearly had the Reich emblems either on each side of the dial or above the dial and I have seen these for sale in the States with high dollar figures not remaining for sale for very long with a “sold” indication in the adds. The emblems being intact greatly effect the value and if the ink or paint stamps of the same emblems are present in the tubes, chassis, speaker then they are snapped up like a duck on a June Bug. Replacement speaker cones are always available usually with the stamp on them as well. Now the part that is quite surprising about how well they work are the pressed paper speaker frame to save on steel and these are always for sale as complete sets or robbed out of a set for sale. Mine is the “tame” or “mild” version without all of these being the first before things totally got out of hand. Between this VE301 and my Philco 444 I can just imagine what came out of the speaker such as Lord Haw Haw, Tokyo Rose and of course Hitler. As for that gold spray coated tube, that one is a CT8 base. They actually hold in the socket quite well. European sets are quite an interesting item including the Early Loewe with that 3NF, 3NFB tube with 3 tubes, including resistors and capacitors within the same envelope and even the later ones are spray coated. These are quite the item.

[phil]

Ive got a large collection of rogers spray shield tubes so I have an array of samples some neat ones that are NIB and some dating back to the Kellog types or at least ones with two way grid pins on top. one of my first sets was a 1929 rogers magestic. i recently saw another for sale on craigslist so I assume they were sold locally. it’s got a plug in thing which is basically a heat element with a plug on it , supposedly to stabilize current spikes I guess. It has a sensitivity control that basicly consists of a copper cup that covers and uncovers one of the coils inside.

some were black and I think they usually had an M prefix while others have the S on them and are grey (or is it the reverse?)
its probably one of the largest collections left. I was originally quite taken by rogers sets. they have nice cabinets. the one I have had a lot of rubber wire that needed replacement. the tube lineup uses some rogers tubes (R30) with an equivalent of the 27 with a different more globe shaped envelope.

I did get my radio to play but after it sitting and moving it maybe i swapped a tube in that wasn’t good or something It had a bad coil in the circuit that had many fine windings and I eventually worked through and found a compatible replacement. I found a spare heater thing , new in the box and it was similar to the one in the rogers set but I think the box says Magestic, not rogers. on mine it has a tin piece above the heater to deflect the heat from it but you can see some heat as affected the top of the set. ive been meaning to revisit why it fils to play as I thought I had restored it quite thoroughly but that was about 20 years ago now.
I’ve hesitated to sell tubes they would fit in a museum or maybe for someone specializing in rogers they would be of value. I dont; really have a reliable tester and hate selling tubes without knowing if they work. I’m aware there is a list of compatible replacements and some like the diodes and some of the others are probably quite hard to find, and many have substitutes. I did find one that was spray shielded but the shielding had partly flaked off to reveal another tube number beneath etched into the glass. , proving they were either counterfeited or perhaps done like that from factory.
on the set it also has some strange tube shields they seem to fit the shape of the R-30 tubes but they aren’t thin tin like most tube shields , these ones are quite heavy and cover only the top 1/2 or so of the tube.

Phil

[Larry]

Did not get all the way thru this so someone else may have contributed this.
I have a sheet that crosses over the spray shield to conventional tube tubes. My understanding ( or perhaps a rumor that circulated when I was more active) is that Rogers bought tubes in bulk from the mfg’s and sprayed and renumbered them to prevent anyone but authorized dealers from doing replacements .
Let me know if the chart is something needed.
Larry

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