I was just wondering... My Sparton AC-62 (retrofitted with 485's instead of the rare Kellogg tubes, sadly) plays just fine for a 7-tube set. And it uses a BH filament-free rectifier. Why did the industry convert to the 80, with its additional filament requiring one more transformer winding? Not enough current through the BH? Too much noise or hum? Less costly? Just wondering...

Advancement of the state of the art, I guess. Remember that the BA and BH tubes were property of Raytheon and the 80 was a development of RCA. The competiveness back then between manufacturers was like a war zone. The manufacturer with the most money and resources won out nearly every time.
Curt

Sparton was one of the few companies that refused to get an RCA license and was able to do well by using tubes and eventually circuits not covered under RCA license.
That was until they finally capitulated (1929?) to RCA and got licensed like the rest of the manufacturers.

They made their own tubes during this time with their unique Kellogg tube equivelent and then the 484/485 for the Technidyne (Equasonne) radios. There were some other tubes including 81 and 50 equivelents (585) and 182, 183 plus a few others I can't recall off the top of my head.

I suppose they chose the BA as it wasn't RCA's tube

I would LOVE to write a book on Sparton!

-Steve
ka8riz

I could be wrong, but I read that in the end it really had little, if anything, to do with RCA/ Raytheon rivalry. Rather, these early cold-cathode rectifiers were simply unstable at what they did. This, from Alan Douglas if memory serves me.

As an aside, I have an old Mohawk brand "B" eliminator (using a Raytheon B-something) that's never been opened up yet still functions fine to this day.

Chris

They really didn't give up on gas rectifiers. The 0Z4 is a gas rectifier used in car radios until 1950's.

BH has a fairly high voltage drop. Drop goes up over time depending on how fast helium seeps out. Many are usable today but in some cases voltage drop has increased. These tubes require extra capacitors in the circuit.

Yup, they had a high voltage drop and a limited lifetime (though I believe the helium gets occluded into the metal plates, rather than seeping out. The gas pressure drops, in any event.).

Raytheon pretty much played that game out, with the 0Z4 and some CK-1005-6-7 rectifiers when instant starting was a requirement. But overall, thermionic rectifiers were simply better.

Yep, GM servicing dealers and franchised or locally chosen servicers had more shelf space for 0Z4s than any other tube! And Delco made the socket so one couldn't handily plug in a 6X5! Neat!

I have gone through some old "Radio Broadcast" magazines, from around 1928, and have to agree with Alan. An ionized helium atom is nothing more than an Alpha particle (maybe with one electron still hanging on). It seems the helium depletion effect gave the tubes such a short life that the theoretically indefinite lifetime was only promised by Raytheon to be good for 1000 hours use.