21-10-2023, 10:17 AM
Also magnetic fields. The Russians used steel sleeves. Most B7G and B9A valves you see have an outer electrostatic (mostly) shield. The tube or mesh you see isn't the anode. Earlier valves used metallisation. Many sets, and all commercial / military, used clip on spring loaded outer electrostatic screening cans (aluminium), and continued to do so for B7G and B9A, which also ensured rough handling didn't shake out the valves. Some valves used metal outer envelopes, especially later USA octal types with button rather than pinch bases, not just EF50 etc.
The 1S5 (DAF91) was very microphonic too.
I've only seen the 1U5 (DAF92) in USA sets, despite it was released in 1945. The 1S5 was 1939, but B7G 1.4V types not used in UK till the 1946 Romac. The Ever Ready Model C used Octal in 1946 and wasn't B7G till 1947 Model C/A. AFAIK all UK sets & mainland European using Philips/Mullard/Telefunken designations used the DAF91 (designed by RCA as 50mA nickel filament 1S5) till 1953 approx. and the DAF96 (25mA tunsten). RCA designed the original nickel filament B7G 1.4V (release 1939 to 1940) based on Sylvania octal 1.4V. The UK edge connect 1.4V were based on the Sylvania Octal. Philips designed the 25mA tungsten 1.4V B7G series, released 1953. Mullard had been a Philips subsidiary from 1928.
I think all my post war USA battery valve sets use the 1U5. I have some early pre-1946 USA "lunch box" AKA "Personal Radios" and they all use the original 1939/1940 RCA types, so 1S5 (DAF91).
However even the DAF96 is prone to stray pickup (maybe not microphonic). Some Pye sets you have to test if more stable with screen on the DAF96 or the DL96. The DK92 and DL94 were still used up to at least 1957 when better HF (DK92, USA used 1L6) or more audio needed (DL94). One Philips set I have uses 2x DL94 in push pull and higher HT on mains (above Philips own spec!) for really loud audio. It uses a DF91 RF preamp and a second DAF91 as phase splitter. However a later version (with added DM70 Magic eye) uses DAF96 detector and DAF91 as phase splitter, a trap for the unwary. So as to get filament power for the added DM70.
Perhaps no-one in Europe licensed the less microphonic 1U5.
https://www.radiomuseum.org/r/philips_lx527ab_2.html
The Colette is more modest on audio using 2x DL96 in push-pull. However it filters grid voltage of the LO (set to about 6MHz on Gram/Tape input selection) and "wastes" a 2nd DAF96 as amp for the active tone controls. The DM70 is used as a triode power phase inverter and power on indicator, not magic eye. So as an experiment I wired the 2nd DAF96 as a phase inverter and the DM70 as magic eye. It didn't make any noticeable listening difference to the tone controls.
Like the sole Vidor VHF-FM & AM set, it unusually doesn't use a DK96 for AM. Instead the 2nd FM IF (DF97) is a Pentode mixer (LO via g2) and 1st FM IF (strangely a DF96) becomes an RF preamp.
https://www.radiomuseum.org/r/philips_co...62_ab.html
I think more strange things done with battery valve portables in the 1940s & 1950s than mains sets. Some German sets use a 1st IF of 10.7 MHz on FM and then the DK96 converts to 6.5MHz IF. Others simply turn off the the DK96.
Most ordinary non-Personal USA MW only (Broadcast) had a RF preamp, but UK and rest of Europe only added that on better multiple SW band sets.
The 1S5 (DAF91) was very microphonic too.
Quote:The 1U5 has the same electrical characteristics but it uses an improved structure which greatly reduces any tendency toward microphonic effects. In addition, the diode unit is effectively shielded from the pentode unit to prevent "play-through". They are not interchangeable since pin allocation is completely different—Radiomuseum
I've only seen the 1U5 (DAF92) in USA sets, despite it was released in 1945. The 1S5 was 1939, but B7G 1.4V types not used in UK till the 1946 Romac. The Ever Ready Model C used Octal in 1946 and wasn't B7G till 1947 Model C/A. AFAIK all UK sets & mainland European using Philips/Mullard/Telefunken designations used the DAF91 (designed by RCA as 50mA nickel filament 1S5) till 1953 approx. and the DAF96 (25mA tunsten). RCA designed the original nickel filament B7G 1.4V (release 1939 to 1940) based on Sylvania octal 1.4V. The UK edge connect 1.4V were based on the Sylvania Octal. Philips designed the 25mA tungsten 1.4V B7G series, released 1953. Mullard had been a Philips subsidiary from 1928.
I think all my post war USA battery valve sets use the 1U5. I have some early pre-1946 USA "lunch box" AKA "Personal Radios" and they all use the original 1939/1940 RCA types, so 1S5 (DAF91).
However even the DAF96 is prone to stray pickup (maybe not microphonic). Some Pye sets you have to test if more stable with screen on the DAF96 or the DL96. The DK92 and DL94 were still used up to at least 1957 when better HF (DK92, USA used 1L6) or more audio needed (DL94). One Philips set I have uses 2x DL94 in push pull and higher HT on mains (above Philips own spec!) for really loud audio. It uses a DF91 RF preamp and a second DAF91 as phase splitter. However a later version (with added DM70 Magic eye) uses DAF96 detector and DAF91 as phase splitter, a trap for the unwary. So as to get filament power for the added DM70.
Perhaps no-one in Europe licensed the less microphonic 1U5.
https://www.radiomuseum.org/r/philips_lx527ab_2.html
The Colette is more modest on audio using 2x DL96 in push-pull. However it filters grid voltage of the LO (set to about 6MHz on Gram/Tape input selection) and "wastes" a 2nd DAF96 as amp for the active tone controls. The DM70 is used as a triode power phase inverter and power on indicator, not magic eye. So as an experiment I wired the 2nd DAF96 as a phase inverter and the DM70 as magic eye. It didn't make any noticeable listening difference to the tone controls.
Like the sole Vidor VHF-FM & AM set, it unusually doesn't use a DK96 for AM. Instead the 2nd FM IF (DF97) is a Pentode mixer (LO via g2) and 1st FM IF (strangely a DF96) becomes an RF preamp.
https://www.radiomuseum.org/r/philips_co...62_ab.html
I think more strange things done with battery valve portables in the 1940s & 1950s than mains sets. Some German sets use a 1st IF of 10.7 MHz on FM and then the DK96 converts to 6.5MHz IF. Others simply turn off the the DK96.
Most ordinary non-Personal USA MW only (Broadcast) had a RF preamp, but UK and rest of Europe only added that on better multiple SW band sets.
