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True Blue?

4/16/2019

1 Comment

 
Harry sent me some tubes.

I try to keep the correct original-type tubes in the radios that are on display. So I had been talking about finding the Arcturus made "Crosley" branded, BLUE tubes for my 1931-1932 Crosleys like the Buddy Boy. Most of these tubes have become harder to find than the radios.

Several causes for replacing the original tubes are likely. First - "OH LOOK AT THAT COOL BLUE TUBE" which has a corollary, "I'LL SELL THE BLUE TUBE FOR $$ AND REPLACE IT WITH A CEAR GLASS TYPE" Second, in my opinion, Arcturas tubes were less than average in reliability. The company was very innovative but this did not translate into longevity both in the tubes and the company. So the original "blue" tubes often had to be replaced.

At this point I should explain what a Arcturus "BLUE"  tube is, but this site has already done a good job:

http://www.bill01a.com/articles/arcturus-a.htm





Picture
Having invented one of the first power pentodes is still not as important as the blue glass, at least in collector appeal.

Here are 2 "PZ" tubes made by Arcturas and co-branded for Crosley. The PZ was developed prior to the RCA 47  (247) but was similar enough to be used in the same circuits. At some point Arcturas had difficulty sourcing the blue glass, even prior to the conversion to ST shaped bulbs. Pictured on the right is another PZ I already had with a clear G bulb.
Picture
And, here is the box in which the blue tube was residing. Do you see any issues?

Well, while being related to a 42 the PZ is clearly NOT. Besides the base configuration (it wont plug in). a PZ is a relative of the 47 which has a 2.5V filament compared to the 6.3V filament of the 42. No wonder it tested SOOO good.

At some time someone must have tested it as a 42 on a TV-7 since it was marked 90(?)/50, a very high reading and indicative of TV-7 test values. No wonder, it was lucky to have survived the test! I know that this was prior to Harry since he does not have a TV-7. Is seems that nobody even noticed the difference, or the 5-pin base (a 42 has a 6-pin base). The tube required a rejuvenation since the high filament voltage had "paralyzed" the cathode. This brought it up to near new spec.
Picture
True, the PZ in the box might have not been the original tube in the box. But even if it had been a "42" we still have a problem here. And true that today just about anybody can print and paste labels, but this tag is very "vintage" and appears in text and color similar to other Arcturus printed material. Note that one of the end-flap tags has also been changed to "42". It does not appear that the other "PZ" label had ever been covered.
Picture
So, no - not true.
1 Comment
Arran
4/16/2019 10:48:12 pm

Russ;
Other then both tubes being pentode power amplifier tubes the #47 and #42 have little in common, the #47 has a directly heated cathode, whereas the #42 is indirectly heated. A closer 2.5 volt analog to a #42 should be a 2A5 I would think.
With regard to the box, I have no idea, wrong tube placed in the box perhaps? It could have even happened at the factory. As you mentioned Arcturus was one of the medium sized manufacturers, and if they were suppliers to Crosley one could believe that they were not exactly high end since Crosley specialized in building inexpensive (I won't insult them by calling them cheap) radios.
They may also explain why Arcturus dropped the blue glass, and for a time lacquered their envelops blue, before witching to the more conventional clear glass. I don't know why sourcing it would have been a problem, unless quartz glass requires different ingredients then ordinary blue glass. Most blue glass is made by adding cobalt to the list of ingredients, and blue glass bottles and jars were very common during this time, such as with a Vicks vaporub jar. I suppose if someone wanted a stand in for blue Arcturus tubes one could dip ordinary tubes in clear blue glass paint/laquer similar to that used on Christmas light bulbs.

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