22-03-2017, 02:31 AM
Another look through the pictures shows that the T99 had what appear to be three coil boxes (I’d guess one each for the input, interstage and oscillator), in which respect it was similar to the T69. If so, then that would be consistent with a single tuned RF stage, with either a bandpass input or bandpass interstage that used the fourth capacitor gang. This would have a variable capacitor section on both primary an secondary sides, but both would be in the same coil box. This is still speculative though, and really needs confirmation.
The T139 appears to have had six coil cans, three each side of the tuning gang, presumably one set for the main tuning and the other for bandspread tuning.
An interesting point is that these Dynatrons units, although associated with that maker’s luxurious radiograms, were also used for the post-WWII Merlin console radio. This started as the B129 with the T69/LF59 combination in 1946, moving to the T99/LF612 combination in 1952 as the B1512E, and then to the T139/LF613 combination, as the R1712ME in 1954.
So inclusion of the T99 in a cabinet with an amplifier and a reasonably well-loaded speaker would not be inconsistent with the heritage. Dynatron did migrate from triode to ultra-linear output stages in its amplifiers in the second half of the 1950s. Its LF20 was essentially a Mullard 5-20. And I suspect that the LF10 was the Osram 912, and the LF15 might have been the ultralinear variant of the Mullard 5-10. The small LF44 (KT61) and LF44A (6AQ5) amplifiers were I think from the triode era, although I am not fully sure. Had Dynatron needed a small single-ended amplifier in the later 1950s – when it was heading somewhat downmarket - I don’t think that it is too much of a stretch to envisage an (SE) ultralinear version of the Mullard 3-3 as fitting the bill.
Cheers,
Steve
The T139 appears to have had six coil cans, three each side of the tuning gang, presumably one set for the main tuning and the other for bandspread tuning.
An interesting point is that these Dynatrons units, although associated with that maker’s luxurious radiograms, were also used for the post-WWII Merlin console radio. This started as the B129 with the T69/LF59 combination in 1946, moving to the T99/LF612 combination in 1952 as the B1512E, and then to the T139/LF613 combination, as the R1712ME in 1954.
So inclusion of the T99 in a cabinet with an amplifier and a reasonably well-loaded speaker would not be inconsistent with the heritage. Dynatron did migrate from triode to ultra-linear output stages in its amplifiers in the second half of the 1950s. Its LF20 was essentially a Mullard 5-20. And I suspect that the LF10 was the Osram 912, and the LF15 might have been the ultralinear variant of the Mullard 5-10. The small LF44 (KT61) and LF44A (6AQ5) amplifiers were I think from the triode era, although I am not fully sure. Had Dynatron needed a small single-ended amplifier in the later 1950s – when it was heading somewhat downmarket - I don’t think that it is too much of a stretch to envisage an (SE) ultralinear version of the Mullard 3-3 as fitting the bill.
Cheers,
Steve
