04-06-2017, 10:12 PM
Thanks for that – it makes interesting reading. As expected, much of the patent refers to the mechanical design of the Fireball front end. An interesting aspect though is that it was also designed for the easy and economical addition of a UHF tuner. Confirmed was the fact that the basic design used a neutrode RF amplifier, although the possibility of using a pentode, cascode or tetrode was mentioned.
In my previous post I said:
That should have read: My guess is that on a minimum-change basis, Jason had just the mixer swap sides, which would indicate that normally the PCC84 (or ECC84) was on the right and the PCF80 (or ECF80) on the left.
That valve disposition was confirmed in the patent drawings; the RF valve (triode with B7G base) was on the right, and the mixer-oscillator (triode-pentode with B9A base) on the left.
Given that the Jason JTV chassis could evidently accommodate a standard turret tuner, the change to the Fireball type for the JTV2 was apparently not driven by a need for compactness. I wonder then whether Jason found the Fireball easier to modify to its own requirements than other types. On the face of it, having all of the channel coils on the same disc, that disc being equidistant from the two valves, would have made doing what Jason wanted easier than with a turret or switched tuner where the various coils were longitudinally separated, and say moving the mixer from the front to the back valve, whilst leaving the oscillator at the front, would have been awkward and would have involved undesirably long wiring connections.
Cheers,
Steve
In my previous post I said:
Re the modified Fireball front end in the JTV2, I wonder how the valve positions compared with the standard UK version. The JTV2 had V1, the ECF80 (RF and MX) on the right looking from the front, and V2, the ECC81, on the left. I can’t find the information for the standard version. My guess is that on a minimum-change basis, Jason had just the mixer swap sides, which would indicate that normally the PCC84 (or ECC84) was on the right and the PCF80 (or ECF80) on the right.
That should have read: My guess is that on a minimum-change basis, Jason had just the mixer swap sides, which would indicate that normally the PCC84 (or ECC84) was on the right and the PCF80 (or ECF80) on the left.
That valve disposition was confirmed in the patent drawings; the RF valve (triode with B7G base) was on the right, and the mixer-oscillator (triode-pentode with B9A base) on the left.
Given that the Jason JTV chassis could evidently accommodate a standard turret tuner, the change to the Fireball type for the JTV2 was apparently not driven by a need for compactness. I wonder then whether Jason found the Fireball easier to modify to its own requirements than other types. On the face of it, having all of the channel coils on the same disc, that disc being equidistant from the two valves, would have made doing what Jason wanted easier than with a turret or switched tuner where the various coils were longitudinally separated, and say moving the mixer from the front to the back valve, whilst leaving the oscillator at the front, would have been awkward and would have involved undesirably long wiring connections.
Cheers,
Steve
