In the US, the sweep tubes that saw application in radio transmitters and linear amps (ham and CB, some commercial) can be crazy expensive everywhere. Usually you have to go to the odd heater voltages to get reasonable prices. 6LQ6 and it's relatives is a good example - $40 to $80 each. Even 31LQ6 is ~$20.
I don't know much about the European types. They may all be rare.
Pete
Here's a side note that you may laugh at. When I was younger and first getting into tubes, I thought "Design Center" meant "The people in the design center chose these values" rather than the center of the design. We all have our "blond moments".
Some of those RF amplifiers used odd heater voltage sweep tubes too, especially the large illegal CB amps. The "Phantom 500" went through several iterations but the later versions ditched the filament transformer and wired 10 X 24LQ6's in series parallel directly across the 120 volt line.
Whoever designed that thing had no clue about RF impedance matching. It used 4 tubes in parallel to drive 6 tubes in parallel. One tube driving 9 would have made far more power. Squeezing 500 watts of RF from 6 tubes made for short tube life....that's why there are no 24LQ6's left in captivity.
Now if I were to make such a thing, it would use a 12BY7 to drive a 6146, which would drive a 4-400 for lots o watts.
Even GE got a piece of that action. They took the 6KD6, added a second cathode connection to pin 6 for better RF performance, and stuck a 13 volt heater inside for "mobile radio" use, and the 8950 was born. Try to find one of those today.
Similarly the "M2057" is an RF version, also with the 13 volt heater, of the 6LF6, one of the biggest sweep tubes around.
So they are, 'cause they're out of production since decades now.
OTOH, a PL519 e.g. never was a cheap valve, especially when made by famous companies, such as ITT Lorenz, Telefunken, Siemens or Valvo. In the 1970ies, when they were widely available from new production, we had to pay about 20 Deutsche Mark per piece, which was about the same as USD 5 to 10 then.
Best regards!
Regarding the lists right at the thread start: PL505 had a 40V/0.3A series heater. It was the first European sweep tube especially designed for colour TV's. But TV's with this tube had a 2nd sweep tube, commonly a PL504 which did the sweep. The PL505 operated as HV source. But there were designs with two sweep tubes and one flyback transformer as well.
I'm not sure if there was a 6.3V/2A heated »EL505«.
Best regards!
I'm not sure if there was a 6.3V/2A heated »EL505«.
Best regards!
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