07-06-2017, 03:53 AM
Here is what Jason had to say about the front end of the JTV2:
“The tuner metalwork is basically the "Fireball" tuner, made in this country by A.B. Metal Products. However, the Jason Laboratories have re-developed the circuitry so that automatic frequency control is now added. Although there are only two valves used, the gain is still considerable. In this form, the tuner would no longer be suitable for reception of television picture signals because the bandwidth is much narrower. It has, however, proved to be the ideal FM and TV sound unit. The circuit is basically simple, as can be seen from the illustrations. The turret plate is a separate part and must be ordered correctly for each area. However, special plates are available with extra positions up to 13, so that coil plates can be provided for any future transmissions.”
From this one might reasonably infer that the TV channel coils, RF and interstage, were configured to provide higher Q than was normal for TV applications. In any event the TV channel oscillator coils would have been different to standard, to provide a 10.7 rather than a 38.15 MHz IF. The FM coils, one for each station, may have been standard, at least if that was the way the TV-FM version of the Fireball was normally configured. But some TV-FM front ends had one wideband FM coilset, with station selection done by fine tuning.
So, it looks as if Jason made, or had made, special turret plates for the JTV2.
Cheers,
Steve
“The tuner metalwork is basically the "Fireball" tuner, made in this country by A.B. Metal Products. However, the Jason Laboratories have re-developed the circuitry so that automatic frequency control is now added. Although there are only two valves used, the gain is still considerable. In this form, the tuner would no longer be suitable for reception of television picture signals because the bandwidth is much narrower. It has, however, proved to be the ideal FM and TV sound unit. The circuit is basically simple, as can be seen from the illustrations. The turret plate is a separate part and must be ordered correctly for each area. However, special plates are available with extra positions up to 13, so that coil plates can be provided for any future transmissions.”
From this one might reasonably infer that the TV channel coils, RF and interstage, were configured to provide higher Q than was normal for TV applications. In any event the TV channel oscillator coils would have been different to standard, to provide a 10.7 rather than a 38.15 MHz IF. The FM coils, one for each station, may have been standard, at least if that was the way the TV-FM version of the Fireball was normally configured. But some TV-FM front ends had one wideband FM coilset, with station selection done by fine tuning.
So, it looks as if Jason made, or had made, special turret plates for the JTV2.
Cheers,
Steve
