Jason FM Tuner

[PJL]

I am looking at a freebee Jason FM Tuner. It's the older type with dial marked 90-105 Megacycles and mottled brown/gold front. This one is without PSU and has 4x EF91, 1x EF80 and a couple of germanium diodes and does not correlate to any in the service sheet which appears to be for later models.

Anyone got any information or perhaps has serviced one of these? I have found various threads and images but Jason seem to have introduced a new model every few months. Best guess is this is a 'fringe' model of the 4 valve version with an extra IF stage and an EF80 for the front-end.

[Synchrodyne]

I think that your guess is right. Most likely it is the original fringe area model, which was available in both Jason (built) and Jasonkit forms.



Full details of the Jasonkit version may be found at this site:

http://ukhhsoc.torrens.org/makers/Jason/index.html

then go to: Directory: "FM_Tuner_Construction_Reprint2" contents...

I have an original of that – please PM me if you want a .pdf version.

There can be differences between Jason and Jasonkit models with the same name, although this does not appear to apply to the very early models.

The original Jason fringe area model seems to have disappeared by the time that the “Matching Equipment” range was released towards the end of 1957.

The original Jasonkit fringe area model survived that event and was superseded late 1958 by the FMT3, self-powered and in a new Jasonkit case shared with the FMT2 and JTV. The FMT3 moniker was also used for a new Jason (built) model released around 1958 August, the same time as the Jason JTV. It would appear that the Jason FMT3 and Jasonkit FMT3 had somewhat different circuits.

The Jason/Jasonkit tuner progression was somewhat complex, and does not seem to have been well documented in hi-fi literature. I think that I have it mostly sorted though, albeit with some question marks.


Cheers,

[Peter.N.]

I had a couple of these back in the day, I think the first one had EF91's and the later one EF80's. They were basically fairly simple and worked very well, I have a number of tapes recorded in the late '50s - early '60s from these mostly on a Philips EL3542 and they still sound good now.

Peter

[turretslug]

The use of an EF80 RF stage and EF91s elsewhere make this tuner iteration an illustrative sidebar to the current "EF91 to EF80" thread!

[David G4EBT]

I have a Jasonkit tuner I bought some years ago, intending to refurbish it just out of interest. (One day perhaps?). I'd long since forgotten about it but recently came across it when rummaging through my 'round tuit' pile in the dark corners of the loft! It looks a bit sorry for itself after years of languishing unloved. It has 4 x EF91s, covers 88-108 MHz, and looking at the layout in 27-page Data Book #12 by G Blundell, appears to be the first one featured. The book is very detailed, with excellent drawings right down to drawing on how to make and drill the chassis. There's also a simple (couldn't be simpler!) PSU design to provide the HT & Heater voltages.

Jason must have been quite an outfit in its day - I remember it featuring prominently in all the magazines. It would be interesting (as with Codar, Nombrex etc, who came and went, almost without a trace), to know of the history of when Jason was founded, how long it existed, how many it employed at its peak and what lead to its demise. Small outfits with a few innovate staff who seized the opportunity and had their moment in the sun.

[PJL]

Here are some pictures of the assumed to be 'fringe' model. There is mention that this front panel was designed to match a PYE amplifier?

I am guessing about 150V HT and 6.3V 1.5A for the heater should get it going. I can see one Hunts brown capacitor lurking in there but the rest are mainly ceramic.

[Synchrodyne]

Originally Posted by David G4EBT

Jason must have been quite an outfit in its day - I remember it featuring prominently in all the magazines. It would be interesting (as with Codar, Nombrex etc, who came and went, almost without a trace), to know of the history of when Jason was founded, how long it existed, how many it employed at its peak and what lead to its demise. Small outfits with a few innovate staff who seized the opportunity and had their moment in the sun.

Some background information on Jason was provided in this thread: https://www.vintage-radio.net/forum/...d.php?p=972670.

To add to that, it would appear that Geoffrey Blundell was the founder, proprietor and chief designer of Jason. I imagine that he had had an RF background, although the initial Jason product was a 3-speed gramophone motor. One would imagine that he saw the imminent start of FM broadcasting in the UK, coupled with the emerging hi-fi components market as an opportunity to deploy his RF capability. Tuners could be problematical for the amplifier-oriented hi-fi organizations, and FM presented even more challenges. Thus FM tuners from a specialist tuner organization were seen as having a definite market niche. Evidently Blundell was also oriented towards the home constructor, as Jasonkit FM models were available from the start. Probably Jason was best known for its Jasonkit tuners, which seemed to have dominated the kitset market, with its built Jason models much more in the background. The Jasonkit FM models appear to have been designed with simplicity and stability in mind, for example using pentodes in all signal stages. Some of the Jason (built) tuners were similar, but others were quite sophisticated. The AM/FM2 of 1957 had an apparent generosity of circuit that one associates more with American tuners of the time.

Another well-known facet of Jason activity was the Jasonkit test instrument range. Possibly this reflected a personal interest on Blundell’s part. Jason may also have provided tuner circuitry to other hi-fi makers; there is certainly strong evidence that the Beam Echo Avantic BM612 was based upon the Jason AM/FM2. (See: http://golbornevintageradio.co.uk/fo...d.php?tid=6846.)

To provide a broader context, it may be mentioned that the other hi-fi tuner specialist of the same period was Chapman, whose founder, proprietor and chief designer was C.T. Chapman. Again, one suspects that he had an RF background, but apparently he had worked for Goodmans, where he was involved with the design of reflex cabinets, and his initial product was a range of such cabinets under the “Ventex” name, with his first AM tuner, the S4, released in 1951. Chapman was an early mover with FM, with its initial FM81 model released late in 1953. However, I don’t think that its FM tuners were quite at the same level, relative to the medium, as its top AM models. Like Jason, Chapman branched out into amplifiers in 1957 (with what were largely “me too” models) suggesting that making tuners alone would not be viable longer term. One way or another, the major amplifier makers had developed their own FM tuners, which probably limited the market for the independent tuner makers as compared with what might have been envisaged when FM was perhaps seen as a difficult proposition best left to the specialists. For example, Leak had engaged Amos and Johnstone of the BBC to do the design work for its original Troughline; Quad had Geoffrey Horn do the prototype design (in 1952) then employed RF-man J.D. Collinson to finish it. Apparently though, Leak did point to the Chapman range for buyers who wanted AM/FM tuners rather than its own FM-only offering. Chapman became part of the Derritron group in 1960, and Chapman tuners – including some solid-state designs introduced in 1963 – remained available until c.1969.

Looking more broadly at the UK hi-fi industry in the 1950s, one could say that RF expertise also existed in Armstrong and Dynatron, both of whom had radiogram chassis backgrounds, albeit at different parts of the market. In fact both were probably better at the RF side than the AF side. They had different futures, but neither was an independent tuner maker in the same way as Jason and Chapman. Lowther also seems to have had some RF expertise, possibly deriving from its pre-WWII radiogram activities, and maybe because its post-WWII owner, Donald Chave, had an interest. But its tuners were essentially adjuncts to its amplifier range, and its total output was probably quite small anyway.


Cheers,

[vidjoman]

Jason kits were popular because back in the day, many Hi Fi items were of home construction and fitted into cabinets similar to a 'home made' radiogram. As a 'kit' it was free of purchase tax and saved about a 50% addon to the price of a factory built one.
I built many of the 'kits' on behalf of the local component supplier who sold the 'kit' to a customer and I built it as a private engineer directly for the customer who saved on the tax. The models evolved into the metal cased longer chassis versions that included a power supply. The early ones often taking power from the power amp already in the Hi Fi cabinet.

[PJL]

Originally Posted by Synchrodyne

http://ukhhsoc.torrens.org/makers/Jason/index.html

then go to: Directory: "FM_Tuner_Construction_Reprint2" contents...
Cheers,

Thanks for this, mine is the fringe model covered on page 17-21 although the layout picture on p19 is different and does not even match the chassis drawing on p18!

[Synchrodyne]

Is yours a Jasonkit or was it built by Jason?

Either way, I am not surprised that there might have been variations over time.


Cheers,

[Synchrodyne]

Here is my best estimate of the timelines for the various Jason (built) and Jasonkit tuner models. It is derived largely from magazine advertisements, articles and items, and Hi Fi Yearbook listings, and almost assuredly does contain errors.

• Jason FM Local Area 1954 – 1957 (no direct replacement)
• Jasonkit FM Local Area 1954 – 1958 (became Jasonkit FMT1)
• Jason FM Fringe Area 1954 – 1957 (no immediate replacement)
• Jasonkit FM Fringe Area 1955 – 1958 (replaced by Jasonkit FMT3)
• Jason AM/FM (self-powered) 1956 – 1957 (replaced by Jason AM/FM2)
• Jasonkit Argonaut AM/FM (self-powered) 1956 – 1959 (no replacement)
• Jason Switched FM 1956 – 1957 (replaced by Jason Prefect)
• Jason Prefect 1957 – 1959 (replaced by Jason Monitor)
• Jasonkit Mercury 1957 – 1959 (replaced by Jasonkit Mercury 2)
• Jason FMS2 (self-powered, cased) 1957 – 1959 (no direct replacement)
• Jason AM/FMS2 (self-powered, cased) 1957 – 1959 (no replacement)
• Jason AM/FM2 (self-powered, cased) 1957 – 1959 (no replacement)
• Jason FMT3 (self-powered, cased) 1958 – 1960 (replaced by Jason FMT4)
• Jason JTV (self-powered, cased) 1958 – 1959 (replaced by Jason JTV2)
• Jasonkit JTV (self-powered, cased) 1958 – 1959 (replaced by Jasonkit JTV2)
• Jasonkit FMT1 1958 - 1967
• Jasonkit FMT2 (self-powered, cased) 1958 – 1967
• Jasonkit FMT3 (self-powered, cased) 1958 – 1967
• Jason JTV2 (self-powered, cased) 1959 - 1967
• Jasonkit JTV2 (self-powered, cased) 1959 - 1967
• Jason Monitor 1959 - 1967
• Jasonkit Mercury 2 1959 - 1967
• Jason FMT4 (self-powered, cased) 1960 – 1967

Cheers,

[PJL]

This tuner came with an Osram Music Magnet 4 I recently purchased and they spent most of their lives in New Zealand.

[Alistair D]

A number of articles were written in Radio Constructor about building these Jason products. Each article contained full electrical and mechanical details so that you could build your own from scratch.

The articles can be found here https://www.americanradiohistory.com...r_Magazine.htm

Jason AG 10 Audio Generator Blundell G. May-59 757
Jason Argonaut AM-FM Tuner-Receiver. Part 1 Blundell G. Mar 56 490
Jason Argonaut AM-FM Tuner-Receiver. Part 2 Blundell G. Apr 56 570
Jason CC 10 Crystal Calibrator Blundell G. Nov-59 274
Jason JR1/JTL Stereo Tape Recorder Unit. Part 1 Blundell G. Sep-61 121
Jason JR1/JTL Stereo Tape Recorder Unit. Part 2 Blundell G. Oct 61 221
Jason JR1/JTL Stereo Tape Recorder Unit. Part 3 Blundell G. Nov 61 295
Jason JR1/JTL Stereo Tape Recorder Unit. Part 4 Blundell G. Jan 62 453
Jason JSA 2 Twin-3-Watt Stereo Amplifier Blundell G. Feb-59 520
Jason Jupiter Stereo Main Amplifier Blundell G. Aug 58 36
Jason Jupiter Stereo Pre - Amplifier Blundell G. Jul-58 884
Jason Jupiter Stereo Pre - Amplifier and Main Amplifier Blundell G. Jun-58 816
Jason Mercury Switched FM Tuner. Part 1 Blundell G. Oct-57 178
Jason Mercury Switched FM Tuner. Part 2 Blundell G. Nov-57 260
Jason OG 10 General Purpose Oscilloscope. Part 1 Blundell G. Aug-59 35
Jason OG 10 General Purpose Oscilloscope. Part 2 Blundell G. Sep-59 102
Jason W11 Wobbulator Caborn R. J. Oct-60 199

Al

[G6Tanuki]

Originally Posted by vidjoman

Jason kits were popular because back in the day, many Hi Fi items were of home construction and fitted into cabinets similar to a 'home made' radiogram. As a 'kit' it was free of purchase tax and saved about a 50% addon to the price of a factory built one.
I built many of the 'kits' on behalf of the local component supplier who sold the 'kit' to a customer and I built it as a private engineer directly for the customer who saved on the tax. The models evolved into the metal cased longer chassis versions that included a power supply. The early ones often taking power from the power amp already in the Hi Fi cabinet.

Purchase-Tax (and its avoidance) was indeed a big issue back in the couple-of-decades following WWII: it was a convenient 'economic lever' that governments could pull or push on when they wanted to stimulate the economy or throttle it back as they perceived was necessary - leading to the "stop-go" economics of the era.

The kit tuner/amplifier/record-player was largely exempt from PT - which could amount to an additional 40% on top of the list-price of a radiogram. Tuners-powered-by-a-socket-on-the-amplifier, and "console/sideboard-style radios" sold with a cutout for a record-player but with this not fitted [your dealer would supply you with a suitable deck as a retro-fit] being examples.

Ads for Jason kit/ready-assembled FM tuners are a staple in the advertising-pages of Practical Wireless for a couple of decades.

Must admit, I'm always perplexed that one of my favourite valves - the little 6AK5 - was not more widely used in UK/European FM tuners: Also, how few of them used the classic Wallman cascode circuit for the RF amp. Were there any tuners [kit or commercial] that used a neutralised 6CW4 Nuvistor in the front-end? That was certainly the 'hot' front-end valve for 144MHz amateur gear in the early-60s.

[turretslug]

I'm sure that I'd heard that the 6AK5 with its unusually good VHF noise performance for a pentode was quite an expensive little valve, presumably it was a somewhat precisely made device as regards grid alignment and cathode coating consistency. The sort of price that the US/UK military would have swallowed but not the budget-conscious '50s VHF/FM enthusiast, perhaps.

Leak must have been pitching the Troughline tuners quite high in the market with their cascode front ends, but I think this technique was almost commonplace with contemporary VHF TV tuners.

I've a couple of Sansui VHF tunerheads in the loft somewhere, one of which uses one 6CW4 Nuvistor in a neutralised RF amp circuit, the other has two of these in a cascode RF amp with an ECC85 mix/osc. The latter one was presumably pitched as something quite serious in the tuner hierarchy at the time.

[Synchrodyne]

As far as I can see, the neither the 6AK5, nor its European counterpart the EF95 were much used in domestic FM tuners, even in the USA where there was, shall we say, a less parsimonious approach to circuit design.

Once the RCA series-cascode circuit (developed from the Wallman shunt cascode) and associated valves became available for VHF TV application (late 1951), this provided a lower noise and almost certainly lower cost option for FM RF amplifiers, with the advantage of using standard consumer valves. Interesting is that in the design of the 6BQ7 cascode double triode valve, RCA followed the 6AK5 in some details. Wallman had used a triode-strapped 6AK5 as the first stage in his shunt cascode circuit.

Nonetheless, in the pre-cascode era, the 6AK5 was found in some American FM equipment. The GE X415 AM-SW-FM receiver of the immediate post-WWII era used no fewer than three, one each for the RF, mixer and oscillator. Perhaps oddly, its XFM-1 FM tuner of the same period had but two, using instead a 6AG5 in the RF position.

In British FM practice, RCA UK used the EF95 as RF amplifier in its New Orthophonic FM tuner of c.1956. And Amos & Johnstone (BBC) specified it as RF amplifier in their WW 1952 September FM tuner design, although subsequently they offered an EF91 option. (Perhaps some would-be builders baulked at the price of the EF95?)

Notwithstanding the widespread use of the cascode RF amplifier in American FM tuner practice, it was not common in British (and for that matter European practice). The Germans, having developed the unit single-valve FM front end and the internally screened ECC85 valve to go with it, seemed determined to stay with that, and from there it spread to the UK. It did eventually find its way to the USA, where it was subject to improvements unknown in Europe. These included asymmetric double triodes, with a frame-grid type for the RF section, triple triodes in which the 3rd triode either allowed a separate oscillator or did the AFC job, and double tetrodes (by which time the AFC was done by a diode).

The UK paradox was that TV-FM receivers, probably seldom intended to provide stellar FM reproduction, mostly used the TV VHF front end for FM, which typically meant a cascode RF amplifier and four gangs.

Pertinent to this thread is that Jason was one of the few UK tuner makers who did use a cascode RF amplifier for FM, and it might well have been the first. The Jason AM/FM of 1956 had an ECC84 cascode RF amplifier with two-gang tuning. I suspect that an aperiodic input was unusual with a cascode. The Jason AM/FM2 had an ECC84 cascode with three-gang tuning. The Jason/Jasonkit JTV of 1958 had a standard TV turret front end, including an ECC84 cascode RF amplifier. The following JTV2 (and the Monitor and Mercury 2) had a modified Fireball turret, using the triode of an ECF80 as a grounded grid RF amplifier.

As already noted, Leak ascended to an ECC84 cascode RF amplifier and three-gang tuning with its Troughline II of 1959, having previously used an EF80 with two-gangs in its original Troughline. The earlier Beam Echo B611 and BM612 tuners both had ECC84 cascode FM RF amplifiers, but these were probably of Jason design. The later BM611 descended to an EF80. I think that there might have been one or two others.

In American practice, I think that FM tuner front ends using cascode RF amplifiers were usually 3-gang, but there were also 4-gang examples, with a bandpass input or bandpass interstage. The use of two RF amplifiers seems to have been rare in the valve era, though. This contrasts with the solid-state era, where during the 1970s, FM front ends with two dual-gate mosfet RF stages ahead of a dual-gate mosfet mixer became commonplace. One example though of a valved receiver with two FM RF amplifiers was the Hallicrafters SX-42 of 1946, which had a pair of 6AG5 RF amplifiers. As the same were used for AM/HF, it could have been that the RF amplifier count was determined more by HF requirements than by FM. I think that the SX-62 followed the same pattern, and these may have been the basis for the Mullard GFR520 of 1949 (which I guess might have used the EF91 rather than the 6AG5).


Cheers,

[Sideband]

Many years ago, I had a Jason FM tuner that I bought for 1 shilling at a jumble sale back in the late 60's. I didn't have to do any repairs to it and it came with an external power supply (which did need repairs). The tuner had four EF91's and just a single tuning control fitted centrally under the scale. It was very well built and worked well. The power supply was somewhat crude and I rebuilt it. It used an EZ91. I remember having to add a couple of 1000pf ceramic capacitors between both anodes and cathode of the EZ91 to get rid of modulation hum. Used it for many years until a house move....no idea what happened to it.

[Synchrodyne]

Jason did include outboard powerpacks as part of its range, both in built and Jasonkit form, as shown in these items:





It would appear that the powerpack was exempt purchase tax, so there was a non-technical reason for separating the tuner and its power supply, at least in the UK.

Other manufacturers also offered similar outboard powerpacks, examples being Chapman, Goodsell and Lowther.


Cheers,

[Peter.N.]

I'm, pretty sure I built one of mine but the other one I don't remember where it came from. Neither had a power supply so I must have knocked something up, or maybe I powered it from my amp as that was home built as well.

Peter

[PJL]

Out of curiosity, I'll clean it up and replace the couple of capacitors and let you know if it is any good. I wonder why they chose point contact diodes but I guess 1954 was before the first transmission so they were probably modelling the design on TV's and the EABC80 would not have been in volume production.

Why anyone would buy a kit and build it before transmissions started is a mystery but maybe there were test transmissions to work with?