29-07-2020, 12:18 PM
(This post was last modified: 29-07-2020, 12:23 PM by Mike Watterson.)
That's why with the 1j29b and 1p24b there is a bit more power possible with the two filaments in parallel rather than series and why series chain B7G battery valves have a complex network of ballast resistors on the filaments.
See graphs of how the filaments have a slight inherent self stabilisation.
The 1j17b is first Generation
The 1j18b is second Generation
The 1j24b, 1j29b and 1j42a are third Generation. I forget if the 1j37b is 1st or 2nd.
You can see for almost twice the power out of a DL94 that the 1j29b is far more impressive than the 1p24b. It comes in 3 versions and in push-pull will deliver considerable power on Audio or RF to over 100MHz.
I should do the two most common 50mA (Nickel filament originally) and 25mA B7G types. You'd probably see a steeper slope on an original 50mA type than much later ones. I'm assuming the DK92 and DL94 from Philips used Tungsten and not Nickel. The 1939/1940 RCA B7G family certainly started as Nickel because RCA didn't have good enough dies or whatever for accurate filaments needed for series operation. Philips was very expert which is why they rather than RCA or Sylvania (first Loctal & Octal 1.4V valves in 1938, same currents as RCA B7G) developed the 25mA types in 1952-1953. The original own design 1.4V valves from Philips were the rimlock models. The P8 base Mullard/Philips in 1939 (and Mazda Mazda Octal) were essentially the Sylvania designs.
The other two interesting battery valve families were the Telefunken squat Y8 types where they were optimised for parallel only, the idea being that mains would use a DEAC as regulator. So they are all different currents and a non-pentagrid mixer-oscillator. Sadly the sets with them are rather expensive as are the valves, used from 1940s up till maybe 1950 as one last German battery valve radio maker held out against the B7G types. The last USA development were the sub-miniature, some in B5A wire ended, initially for military radio, mostly by Raytheon. The true hearing aid types seem to be a parallel development in the same B5A package as often those are lower HT and 1/2 a single cell filament. I have some NOS of those including B7G cans with coils and the B5A valves inside, maybe for a PRC25. The 1V6 was used also in 1950s domestic USA and Japanese pocket sets as well as a few continental models. It's a Triode-Pentode and allegedly better performance than the battery pentagrids due to less FM of the LO and less leakage of LO on RF in.
https://www.radiomuseum.org/tubes/tube_1v6.html
See graphs of how the filaments have a slight inherent self stabilisation.
The 1j17b is first Generation
The 1j18b is second Generation
The 1j24b, 1j29b and 1j42a are third Generation. I forget if the 1j37b is 1st or 2nd.
You can see for almost twice the power out of a DL94 that the 1j29b is far more impressive than the 1p24b. It comes in 3 versions and in push-pull will deliver considerable power on Audio or RF to over 100MHz.
I should do the two most common 50mA (Nickel filament originally) and 25mA B7G types. You'd probably see a steeper slope on an original 50mA type than much later ones. I'm assuming the DK92 and DL94 from Philips used Tungsten and not Nickel. The 1939/1940 RCA B7G family certainly started as Nickel because RCA didn't have good enough dies or whatever for accurate filaments needed for series operation. Philips was very expert which is why they rather than RCA or Sylvania (first Loctal & Octal 1.4V valves in 1938, same currents as RCA B7G) developed the 25mA types in 1952-1953. The original own design 1.4V valves from Philips were the rimlock models. The P8 base Mullard/Philips in 1939 (and Mazda Mazda Octal) were essentially the Sylvania designs.
The other two interesting battery valve families were the Telefunken squat Y8 types where they were optimised for parallel only, the idea being that mains would use a DEAC as regulator. So they are all different currents and a non-pentagrid mixer-oscillator. Sadly the sets with them are rather expensive as are the valves, used from 1940s up till maybe 1950 as one last German battery valve radio maker held out against the B7G types. The last USA development were the sub-miniature, some in B5A wire ended, initially for military radio, mostly by Raytheon. The true hearing aid types seem to be a parallel development in the same B5A package as often those are lower HT and 1/2 a single cell filament. I have some NOS of those including B7G cans with coils and the B5A valves inside, maybe for a PRC25. The 1V6 was used also in 1950s domestic USA and Japanese pocket sets as well as a few continental models. It's a Triode-Pentode and allegedly better performance than the battery pentagrids due to less FM of the LO and less leakage of LO on RF in.
https://www.radiomuseum.org/tubes/tube_1v6.html
