Jason FM/TV sound tuner

[Synchrodyne]

The remainder of the then-current Jasonkit range was also advertised in HFN 1958 September, but on a different page:

   

The Jasonkit tuner list comprised the two original FM models, plus the Argonaut AM/FM unit and the Mercury switched FM unit.  The 10+10 watt stereo amplifier was probably the Jasonkit version of the Jason J2-10, I think sometimes named as the Jasonkit Jupiter.  And likewise, the forthcoming simplified stereo amplifier was probably the Jasonkit version of the JSA2, and its matching tuner would have been the Jasonkit FMT2 or FMT3.  The Jason/Jasonkit FMT3 would directly replace the original fringe area FM tuner.

The Jason J2-10 and JSA2 were also both advertised in HFN 1958 September:

   

This advertisement for Jason products appears to be from 1958 August, and includes the JTV:

   

And this I’d place as being from late 1959, which was when the Mk III amplifiers were released:

   

It referred to the Jason JTV2, but the picture shows the JTV!  Perhaps there were not yet any JTV2 production samples to photograph when the copy was prepared.  In the Jasonkit series, the JTV was mentioned, but said to be the same as the Jason JTV2!  So that was on the cusp of the transition from the JTV to the JTV2.  Note that by then the Jason FMS2, AM/FMS2 and AM/FM2 were no longer mentioned.  The Jason Prefect local area switched FM tuner was still in the range, though.  I suspect that the new JTV2, with fringe area performance, was seen as being a suitable replacement for the fringe area FMS2.  The AM/FM models, with MF-only coverage on AM, might not have sold so well.  The AM/FM2 was anyway a “luxury” model, with no fewer than 11 valves.  (Strangely, the Beam Echo Avantic BM612, announced in HFN 1958 September, also had 11 valves and a very similar specification.  I wonder of Beam Echo used the Jason circuit?) 
   
Interesting would be what, if any announcement Jason made when the JTV2 replaced the JTV.  My guess is that it would have focussed on fringe area capability and AFC.  I think one would have to search HFN for say the last quarter of 1958 and first quarter of 1959 as likely places to find such.

In 1960, the Jason Monitor replaced the Prefect, and the essentially identical Jasonkit Mercury 2 replaced the Mercury.  Both the Monitor and the Mercury 2 used the JTV2 circuit, sans power supply.  Now, the remaining Jason/Jasonkit switched tuners were all of the FM/TV sound variety, with none being FM-only.  Demand for switched FM-only tuners had probably peaked and was on the wane by then.

   

And later in 1960, the Jason FMT4 replaced the Jason FMT3.  But there was no Jasonkit FMT4; rather the Jasonkit FMT3 stayed in place.  So, now there were one Jason FM-only tuner, two Jason FM/TV sound tuners, three Jasonkit FM-only tuners, and two Jasonkit FM/TV sound tuners.  All of those models lasted until the demise of Jason.  Clearly, FM/TV sound tuners were an important part of the Jason product line.  Once Jason departed, there was, in the UK at least, a gap until 1971 when Lowther re-entered and Motion Electronics entered the TV sound tuner market, the former with a UHF-only model and the latter with VHF and/or UHF options.  Although the JTV2 lasted into the UHF TV era, by then Jason appeared to be inactive in development terms, so there was no derivative that included UHF or an UHF add-on device.  Likewise, as far as I know, Jason never developed an FM multiplex decoder for the FMT4.

   
 
Comparing the JTV and JTV2 chassis, it may be seen that the JTV2 layout was reversed, with the front end on the left-hand side rather than the right.  So, the apparently larger-than-necessary front end  cutout in the JTV2 chassis was not the result of carryover of the JTV chassis.  Perhaps it was originally planned to use a standard turret for the JTV2, but a late change was made to the much more compact Fireball type.  And possibly this one done in part to facilitate the very compact chassis used for the Monitor and Mercury 2.

Cheers,

Steve

[Synchrodyne]

Re the JTV front end, my working assumption has been that it was a modified TV-FM 12-position turret.  The modifications would have been the use of E-series rather than P-series valves (which was very likely an export option anyway) and the modification of the TV channel “biscuits” to provide a 10.7 MHz IF.  But standard FM biscuits probably could have been used, given that some TV-FM front ends were designed to provide a 10.7 MHz IF on FM, but 38.15 MHz on TV.

But it might have been simpler than that.  With the start of Band III TV transmissions in the UK, some front end makers produced units that could be used to modify existing Band I-only superhet receivers to receive cover Bands I and III.  Cyldon and Brayhead appear to have been the main practitioners here, offering variations on their standard turret tuners, the TV12 in the Cyldon case.  These conversion units were available with “E”, “P” or “U” series valves as required to match specific receivers, with a range of IFs, typically covering 10, 16 and 38 MHz groups, and with oscillator low or high as required.  The IFs had a reasonable range of adjustment around their nominal values.  I think that Cyldon offered a wider range than did Brayhead.

A couple of examples of such conversion front ends were the Cyldon E10L, with “E” series valves, 10 MHz IF and oscillator low, and the Brayhead 10P, 10.5 MHz sound IF and “E” series (Parallel heater) valves.  With either of these, the IF would have been adjustable to 10.7 MHz, so for the JTV, the TV channels could have been covered with standard components.  These conversion units would not normally have covered FM frequencies, but their respective makers’ standard FM biscuits (for 10.7 MHz) would have fitted.

So, the JTV front end might have been comprised of all standard components.

I do not know whether the JTV front end was oscillator-low or oscillator-high, but then it would not have mattered very much for this application.  Band I-only superhet TV receivers with the sound IF around 10 MHz were mostly oscillator-low as far as I know, so 10 MHz conversions units may have been available only as oscillator-low.

I’d guess that the demand for conversion units would have waned by the end of the 1950s, so they were probably withdrawn from production about then.  That would have been another reason for Jason to develop a bespoke solution for the JTV2, if in fact had gone the above suggested route.

In the HFN 1958 September article attached upthread, there is a picture of a turret biscuit, which is of the single-piece form.  That might outrule a Cyldon TV12 derivative, as I think that had two biscuit pieces per channel.

Cheers,

Steve

[Synchrodyne]

In post #34 upthread, I said:

“Interesting would be what, if any announcement Jason made when the JTV2 replaced the JTV.  My guess is that it would have focussed on fringe area capability and AFC.  I think one would have to search HFN for say the last quarter of 1958 and first quarter of 1959 as likely places to find such.”

That should have been last quarter 1959 and 1st quarter 1960.

Anyway, there is a comprehensive Hi-Fi News (HFN) index at this site:  http://ukhhsoc.torrens.org/other/Indexes/index.html. 

In particular it shows that there was an article in the 1959 October issue, page 316ff, by G. Blundell (of Jason) entitled “New TV and FM Tuner for constructors” , with Part 2 of the same appearing in HFN 1959 November page 394ff.
 
I’d say that there is a good chance that this two-part article described the Jasonkit JTV2 (and/or the Mercury 2) and if so, may have given the reasons for the issue of a new design just 13 months after the original JTV was released.  (I have not seen the two HFN issues at interest.)

Cheers,

Steve

[Geordie McBoyne]

From the 10th September 1960 Wireless and Electrical Trader magazine.  
Another FM and TV sound tuner.

Geordie McBoyne.

[Murphyv310]

That looks like a fireball tuner in there.

[Synchrodyne]

That is almost certainly a rebadged version of the Jason Monitor.


Cheers,

Steve


   

[Ed_Dinning]

Hi Gents, wasn't there a Jason wobbulator that used a fireball tuner?
I believe the circuit and details were featured on the front cover and inside a 1960's copy of Radio Constructor.

Ed

[Alistair D]

Absolutely correct Ed. It was called the W11

Some pictures and info here.

http://www.g1jbg.co.uk/test13.htm

Al

[Synchrodyne]

Here is the brochure for the built version of the Jason JTV:

           

It had an apparent date of 1958 September, so I’d say it was the original issue.

And here is the brochure for the Jasonkit range, with apparent date 1958 August:

       

The Jasonkit JTV was included, but not under its definitive model name.  Rather it was described as the “Switched FMT/TV Sound Tuner”.

It looks as if the decision to use the “JTV” name for both the Jason and Jasonkit versions was made a little later on.

In that vein, the “Fringe F.M. Tuner” listed was not the original version, but what was later designated as the Jasonkit FMT3.  The “tells” are the fact that it was described both as having variable AFC, and being self-powered.  The original fringe area circuit had neither of these features.  I think it was a few months later that Jason started using the FMT3 designation for this Jasonkit model, at the same time adopting the Jasonkit FMT1 name for the “Standard F.M. Tuner”, and adding the Jasonkit FMT2 as an in-between model.  But the Jason FMT3 name was used for the built version of the new fringe area tuner, a contemporary of the JTV, from the start.

That Jasonkit brochure also previewed the forthcoming Jasonkit instrument range.

Re the use of a modified Fireball front end in the Jason/Jasonkit JTV2, I think we have established that it was not chosen for its compactness, as there would have been room on the chassis to mount a standard turret-type tuner.  On the other hand, it probably was essential for the Jason Monitor and Jasonkit Mercury 2 models, both very compact units.  For the most part, these shared the JTV2 circuit.  One may infer that Jason was looking to rationalize its tuner range, with all switch-tuned models being of the FM-TV sound type, no FM-only versions.  Effectively the Monitor replaced the Jason Prefect, with an “upgrade” from local area to fringe area performance, and the Mercury 2 replaced the Jasonkit Mercury.  One could also argue that the Jason JTV2, as well as being the successor to the Jason JTV, was also the logical replacement for the Jason FMS2.


Cheers,

Steve