Before you start reading
In 2017 I first uploaded what has become pt1 of the on-line Philips TV Tuner History story, which ultimately grew to the 6 parts that you find on this site. After posting the first version I have received many additional inputs and stories, that have allowed me to extend and improve the history to a level that seems to be very complete. In any case the flow of additional data has almost dried up (it will never stop completely of course), which has allowed me to move to the next step: converting the on-line story to real books. As a fervent history reader and book lover I find that there is nothing more beautiful than a good book. With a solid fact-based historial story, but also many pictures, schematics, and overviews. Also quite some readers of the site asked me if and when I would publish it.
I have now come to this point. October 2023 the first volume of my Philips Technology History series will be formally released, covering the period 1950 to 1980. This first volume is based on the on-line Tuner History pt1 to pt3 plus the Remote Control History page. All text has been thoroughly reviewed, corrected, updated, and extended, such that it is now hopefully 99,9% bug and error-free. The Tuner Basics sections have been extended, while new sections on Central Antenna Installations (CAI) and cable networks have been added. All pictures have been refreshed and where possible improved. In other words, the book is more than the sum of the on-line pages!
As a consequence, and to reduce the amount of maintenance, I have reduced the original on-line histories to their core tuner story. All the "surrounding" stories on technologies and the organization can now be found in the book. The on-line story has thus been reduced to the core technical tuner history, such that it can still act as an on-line reference for vintage electronics enthusiasts. In this way I hope to satisfy both target audiences: the real Philips history lovers with the books, the engineers with the on-line overviews.
I have now come to this point. October 2023 the first volume of my Philips Technology History series will be formally released, covering the period 1950 to 1980. This first volume is based on the on-line Tuner History pt1 to pt3 plus the Remote Control History page. All text has been thoroughly reviewed, corrected, updated, and extended, such that it is now hopefully 99,9% bug and error-free. The Tuner Basics sections have been extended, while new sections on Central Antenna Installations (CAI) and cable networks have been added. All pictures have been refreshed and where possible improved. In other words, the book is more than the sum of the on-line pages!
As a consequence, and to reduce the amount of maintenance, I have reduced the original on-line histories to their core tuner story. All the "surrounding" stories on technologies and the organization can now be found in the book. The on-line story has thus been reduced to the core technical tuner history, such that it can still act as an on-line reference for vintage electronics enthusiasts. In this way I hope to satisfy both target audiences: the real Philips history lovers with the books, the engineers with the on-line overviews.
Introduction
After having dived into the history of my father's 1948 home-built TV, early Philips television development, and the EQ40/EQ80 enneode, it is almost logical to tackle the next topic: the TV tuner. On the one hand the tuner is one of the key functions in a television, which has - being an RF engineer - my warmest attention. But secondly it is again a very personal story because I've been active in the development of tuners and their key components for 25 years. And thirdly there is a certain nostalgia, because in today's internet-connected Smart TV's tuners hardly have a function any more, also because terrestrial off-air transmissions have almost completely stopped. This story is thus also a tribute to a very complex building block and the people that worked on making it ever better, smaller, cheaper and more advanced.
Although there have been many brands of tuners - initially every self-respecting TV set maker also designed its own tuner - I will again use Philips as the representative storyline. Not because they were necessarily the first or best in every aspect (although Philips was of course good and quite innovative), but it definitely was a representative player, being active from the first post-war TV until a few years ago, ending as one of the three biggest tuner manufacturers and one of the two surviving set makers with a tuner activity (Matsushita-Panasonic being the other ones). Furthermore Philips was a classical vertically integrated company, with all components, the (tuner) module and the final TV sets all produced in house. Like for the television history I will focus on the technical developments (concepts, key components, construction) without ignoring aspects like organization that provide the nostalgia. I will cut the story into multiple parts, linked to the key components and underlying RF technologies: - 1945-1958 : valve-based VHF tuners - 1959-1965 : valve-based UHF tuners - 1963-1975 : transistor-based tuners - 1975-1990 : IC-based tuners and frontends - 1990-2000 : MOPLL and maturity - 2000-2014 : integration and silicon tuners Because the tuners were always part of a bigger system (television of course, but later also the video recorder (VCR), satellite or cable set top box (STB), and PC) I will cover the high-level history of these applications. This will put the tuner development in a much broader perspective, but is also necessary to explain the organizational developments in and around the tuner organisation. As we will see, these had a major impact on what will turn out to be an exciting history. |
Chapter navigation
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Tuner basics 1 - down conversion
The basis of all radio-based broadcasting and communication systems is always the same: information (which was in the past of course always analogue, today almost always digital) is modulated onto an RF frequency carrier signal, fed to an antenna and then transmitted into the ether as electro-magnetic waves. In this story RF (Radio Frequencies) means carrier waves above 50MHz and below 1GHz. For the tuner story the actual modulation format of the carrier is fairly unimportant, but for the analogue television that we're looking at it is of course Amplitude Modulation (AM), or more precisely Vestigial Side Band Amplitude Modulation (VSB-AM, or simply VSB), where one of the two classical AM sidebands has been largely filtered away. The initially more relevant parameter is the bandwidth of the modulated signal, which is more or less equivalent (but not identical to!) the Channel Bandwidth. For early TV standards the channel bandwidth was still in the order of 5-6MHz, but then quickly settled on mostly 7 and 8MHz. This means that all information of each transmitted TV channel is contained within a frequency band equal to the channel bandwidth.
At the receiver side an antenna picks up the much weakened EM waves of the transmitted signal, translating them into electrical signals equivalent with the modulated carrier wave. This is where the tuner comes in, because it is the module directly behind the antenna. The tuner function performs at the highest level two operations: 1. to translate the RF signal to an easier to handle lower frequency, which is referred to as the Intermediate Frequency (IF), and 2. to filter out only the wanted signal. We will start with point 1.
At the receiver side an antenna picks up the much weakened EM waves of the transmitted signal, translating them into electrical signals equivalent with the modulated carrier wave. This is where the tuner comes in, because it is the module directly behind the antenna. The tuner function performs at the highest level two operations: 1. to translate the RF signal to an easier to handle lower frequency, which is referred to as the Intermediate Frequency (IF), and 2. to filter out only the wanted signal. We will start with point 1.
To the right is the block diagram of a typical RF receiver, in this case a TV Tuner. For the first basic function we only need to look at the three active elements: the pre-amplifier, the oscillator and the mixer. As close as possible behind the antenna a low noise pre-amplifier amplifies the signal with the main objective to guarantee a good Signal-to-Noise Ratio (SNR). In every step of the television receive chain a bit of noise is added to the signal, so by amplifying it to a sufficiently large level the influence of these later noise additions is minimized. In the ideal case - which is never achieved - only the noise of the pre-amplifier determines the SNR.
The output of the pre-amplifier is fed to the mixer, which on a second input obtains the output of the Local Oscillator (LO). The mixer needs to have a highly non-linear characteristic versus the input voltage, which means that it effectively performs a multiplication of its two input signals. So if the (unmodulated) RF input signals is a sine wave sin(2.pi.fc-t) (with fc the carrier frequency) and the LO output signal sin(2.pi.fLO.t) then the mixer output will contain in theory all frequencies m.fLO +/- n.fc, with m and n integers . This is shown in Fig.2. For a receiver only one combination is of interest: m=1 and n=-1, or the resulting frequency fLO-fc. If the LO frequency is slightly higher (say 30MHz) than the carrier frequency the resulting output signal will be a down-converted carrier at 30MHz. This difference frequency is called the Intermediate Frequency (IF). All other mixing products of the RF and LO signal are at much higher frequencies, which means they can all be filtered with a Low Pass Filter. The output of the mixer, after filtering, is then only the down-converted modulated carrier at the IF. |
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First generation non-tuning television receivers, 1947-1950
For the first years of television broadcast the situation was still straightforward: in principle the owner of a television set was able to receive signal from exactly one transmitter. In the UK this was either Alexandra Palace in London or Birmingham, in France Paris (from the Eiffel Tower) or Lille, in the Netherlands initially the Philips Experimentele Televisie from Eindhoven, later Lopik/IJsselstein. The RF receivers of the first generation post-war televisions where thus set to the single RF channel transmitted in the area where the set was sold. So although some filtering did take place, the basic concept of the television receivers of the Philips TX380, TX390 and TX400 platforms (from 1948, 1949 and 1950, respectively) was as shown in Fig.2.
The first post-war commercial television sets from Philips were the 463A and 563A, for the 405-line UK market and designed by the Mullard Labs in Mitcham, South London. It was a 1946 design and clearly based on pre-war televisions. The 463A was a television-only, but the 563A combined television and radio reception. To this end it had the unique concept of separate mixer-oscillators for both video and sound, allowing the sound MO and IF chain to be shared between television and radio mode. This resulted in a very complex arrangement of tuned circuits for four (!) bands around the sound MO. Clearly this was a too radio-centric design, essentially a television built around a radio instead of the other way round, and this concept was never re-used in any other Philips TV set.
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The picture left shows the RF receiver front end of the Philips 385U, a set for the UK from 1949. It was based on a platform design by the Apparaten Lab (Devices Laboratory) in Eindhoven but product development was done in the Mullard Labs in Mitcham. It also introduced the much more compact 40-series Rimlock valves. The set was produced in two versions, one for London, where the Alexandra Palace transmitter station used the picture carrier frequency of 45MHz, and one for Birmingham, with a transmit frequency of 61,75MHz. In case the TV owner moved from one region to the other the set had to be re-aligned in a service work shop.
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From the circuit diagram we can see that the amount of filtering in this front end was still minimal. At the input is a matching network to transform the 300 Ohm antenna impedance to one better matching the UF42 g1 input impedance. There is a tuned Band Pass Filter (BPF) between the first and second stage, while a single-tuned serial filter S13-C31 in the feedback loop of V10 sets the oscillation frequency of the self-oscillating mixer in the second UF42 pentode. The gain of the first amplifier could be adjusted through the voltage of the line marked "Brightness". This was connected to a potentiometer for a fixed setting, and thus not an Automatic Gain Control (AGC); that would come only later. A front end as shown here was the most basic form of receiver.
A one step more advanced concept for a single channel receiver is shown here, the front end of the TX594U 625-line set. The input stage B10 (using an UF42) is almost identical to the one above of the 385U. However, the mixer and oscillator functions have been separated at the expense of an additional UF42 pentode (B12). The oscillator is a Colpitts, with direct (positive) feedback from g2 to g1 through a tuned circuit S9-C10-C11-C12. Through C9 the oscillator signal is fed directly to the g1 of the UF41 mixer (B11). In theory this arrangement should be optimal for performance; every function properly separated for maximum isolation and minimum crosstalk. At the same time the cost is high (three pentodes), so it will take another three years before we see it back in standard tuners.
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In practise the oscillator of the TX594U seems not to have been very good, despite its dedicated pentode. Especially when the set heated up it had the tendency to run away in frequency. At the time television sets didn't yet contain Automatic Frequency Control loops, and oscillators had to be intrinsically stable, but apparently they were not. Many of the surviving sets thus had additional variable capacitors with an external knob on the side of the set for corrective tuning.
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A similar but slightly cheaper implementation of this concept was used in the TF651A, the first Philips television set for the new French 819-line standard. But instead of a pentode it used the cheaper EC81 triode, a valve not applied in any other Philips TV set. The French standard posed a number of challenges: it was the first to use the VHF-III band (the Paris Eiffel Tower transmitted at 185,25MHz), and secondly it had much higher bandwidth (14MHz per channel). Especially to cope with the latter requirement, the picture-IF of the TF651A was moved up to 36,15 MHz. (For comparison, the IF of the previous three receivers was around 13MHz). Finally it is noteworthy that the front end was designed for a 75 Ohm asymmetrical antenna, as opposed to the standard 300 Ohm dipole.
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Tuner Basics 2: Channel selection
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The first 4-channel tuner, 1951
The TX400U-00, the first version of the TX400U, the very first commercial 625-line "Gerber-norm" television, still contained a single-channel front end as in the first generations. As such it was launched in 1950, just before the start of 625-line TV transmission in The Netherlands. But already the next year an updated version was introduced, the TX400U-01, containing the first real tuner. Simultaneously this module was introduced in the standard version of the TX500U (with 12" display) and TX700U (a large screen rear projection model). The first 4-channel tuner was coded A3 421 82 (used in the TX400U-01 and TX500U-00) and had an asymmetrical 75 Ohm input, but it was quickly superseded by the A3 694 42 with a 300 Ohm symmetrical antenna input (it was implemented from the TX400U-04 and TX500U-04 versions). These tuners introduced a few important innovations:
1. Multi-channel tuning, in this case 4 channels
2. A dedicated tuner module. Until then the RF front end was simply built on the main chassis as part of the integral RF-IF-video/audio chain. In most cases there had been no RF shielding of the tuner section. With the A3 421 82 a dedicated tuner module was introduced, placed on top of the chassis, and providing proper RF shielding.
3. Noval valves, in this case the EF80, replacing the Rimlock EF42 or UF42. This didn't necessarily mean a major performance improvement, because neither the EF/UF42 nor the EF80 were dedicated RF valves; they were both essentially IF and baseband valves.
1. Multi-channel tuning, in this case 4 channels
2. A dedicated tuner module. Until then the RF front end was simply built on the main chassis as part of the integral RF-IF-video/audio chain. In most cases there had been no RF shielding of the tuner section. With the A3 421 82 a dedicated tuner module was introduced, placed on top of the chassis, and providing proper RF shielding.
3. Noval valves, in this case the EF80, replacing the Rimlock EF42 or UF42. This didn't necessarily mean a major performance improvement, because neither the EF/UF42 nor the EF80 were dedicated RF valves; they were both essentially IF and baseband valves.
Comparing the circuit diagram of the A3 694 42 with the previous single-channel front ends, we see that it has increased in complexity, although the input matching, the brightness control through the g1 voltage of B8 and the output filter remained more or less unchanged.
For this first tuner the designers had chosen capacitive tuning. So the inductors of the BPF channel filter (S27-S28) and the oscillator (S29+S30) were fixed, while the channel tuning was accomplished by simultaneously varying the BPF capacitor C64 and the oscillator tank circuit capacitors C70 and C71. |
The complexity of the tuning function should not be under-estimated. For tuning from channel 1 to 4 in the VHF-I band the BPF central frequency has to move from 43,5 to 50,5, 57,5 and 64,5MHz, while the LO frequency moves from 80,15 to 87,15, 94,15 and 101,15MHz. (In the TX400 platform the picture carrier IF was 23,5MHz). For each of the channels the error between the desired BPF centre and the LO should not be more than 100-200kHz to avoid picture or sound distortion. Especially the BPF had to tune in a linear way over a range of more than 30%, the LO more than 20%. It is thus not surprising that around the BPF and especially the oscillator there are a number of trimmers to guarantee a smooth and constant joint tuning of the BPF and LO. C66, C69 and C72 were all adjusted in the factory for optimal alignment at the upper edge of the band, and were trimmed at 64,5 and 66,75MHz. Other alignments were the IF output filtering, where S31 was tuned to the centre of the IF pass band (19,75MHz) and S32 was a trap at the picture carrier of the next channel (23-7=16,5MHz).
Interior and top view of the Philips A3 694 42 4-channel capacitive tuner. The core BPF and LO inductors are mounted on a common rod for magnetic coupling. The compartment on the right contains the input circuit, pre-amplifier and BPF and is shielded from the compartment on the left containing the LO, mixer and IF output. The picture on the right shows the three capacitive and two inductive alignment points of the tuner. [Philips TX500 Service Manual]
AT7501, 10-channel capacitive tuner, 1952
Already the next year, 1952, yet another upgrade appeared: the 10-channel capacitive tuner AT7501. It obviously was not possible to tune across the combined VHF-I (40-68MHz) and VHF-III (174-223MHz) bands, and therefore the tuning range was split into two sections, one for each band. Because combining a dual band tuner with a self-oscillating mixer-oscillator made it all too complex, the first modification was the introduction of the ECC81 as mixer-oscillator; one triode acting as oscillator, the other as mixer. The EF80 pre-amplifier remained essentially unchanged. Because it is impossible to match antenna impedance to the EF80 input impedance over the combined VHF-I and III range, also the input stage now became not only band-specific but also tuned. As a result the tuner was the first to have three jointly tuning circuits (input match, BP channel filter and oscillator tank circuit), and all three of them duplicated for VHF-I and VHF-III. A switch linked to the capacitor stepping mechanism would would flip between channel4 (VHF-I) and 5 (VHF-III).
The schematic on the right, from the TX1410U television, is clearer in showing the concept of the tuner (although this one is less clear on the switching, for that the TD1420 tuner diagram is better). The green and red zones show the different ways of oscillator-to-mixer coupling. For VHF-I (green) it is done inductively, with a small coil S10a coupling into the secondary of the BPF. For VHF-III it is done capacitively using C39. Also note that the IF output uses galvanic decoupling from the tuner through S7, a concept so far only used in the TF651A tuner.
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One of the new functions the AT7501 needed, in the meantime, was band switching. In the above circuit diagrams is visible that the input matching filter, BPF and LO tank for each band VHF I and VHF III were switched with 7 switches each, so 14 in total! (The TD1420 schematic diagram is again the one illustrating this best). The question is how these 14 switches were operated. To this end the AT7501 introduced a first of many mechanical innovations that we will see in the coming generations of (VHF) tuners. Mechanical designers were at least as important in tuner design as electrical engineers, and tuners will increasingly be superb multi-disciplinary technology solutions!
The AT7501 band switching assembly, as visible in the picture on the left, can be described as follows. On the tuner axle, which is rotated by the front panel tuning knob, a bended band ring is mounted. For VHF-I the ring is "high"as shown on the picture, for VHF-III it bends to a lower height. This ring runs through fixed wheels, mounted on the tuner frame. When turning the axle through the band switching position, the lower height of the ring will force the entire switch assembly forward along the axle axis. This movement is transferred through the switch bracket to the switch arm, which will move outward as shown by the yellow arrow. Inside the tuner the 14 switches are mounted, where for each position of the swith arm (in and out) seven switches are closed.
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The AT7501 was used from 1952 in the TX1410 platform, with the main family members TX1410, TD1410, TX1714, TD2314 and TD1420. Also the earlier TX400, TX500 and TX700 received field upgrades using this tuner, which had factory code A3 694 76 and (with slight modifications) A3 695 27. The IF used in this platform was still 23,5MHz picture carrier and 18,0MHz sound carrier, with two remarks; firstly in volume 3C of the "Electronic Valves" series of Philips from 1953, the AT7501 is used in the reference diagram of a 625-line television receiver with IF's at 23,75 and 18,25MHz, for picture and sound, respectively. It is unclear where this comes from, and as far as I know these values have never been used in a real TV set. I therefore still hesitate whether the AT7501 and A3 694 76 are 100% the same or not. Secondly, two later sets of the TX1410 platform, the TX1410U-48 (an NTSC set for Argentina) and the TX1714A both introduced slightly higher IF values with a picture carrier at 26,1MHz and sound IF at 21,6MHz (the TX1410U-48) and 20,6MHz. As far as I can see these were the only two sets using these values, which was almost certainly an intermediate step towards the new higher IF at 38,9MHz that would come with the next generation.
Although it introduced the 10-channel tuner, the AT7501 was still a mediocre solution because of one specific item: the EF80 simply was no RF valve. There were two reasons for this. The first and fundamental issue is that pentodes are simply noisier than triodes. Because part of the electron flow out of the cathode is received by the screen grid g2, at the anode this results into "missing electrons" with a statistical behaviour, which can be translated into an additional effective noise contribution. But secondly the EF80 was primarily an IF valve, with higher parasitic capacitances due to the larger grids, that had a negative effect on its high frequency gain and noise performance. Noise Figure was therefore particularly bad, and in practise the EF80 was often replaced by the fully compatible Telefunken EF800, which had considerably better noise and microphony performance. Telefunken, however, was the biggest European competitor of Philips and it was against all corporate policies to use their valves. These were therefore imported by the Philips Sweden organization for delivery to the local Service organizations. Clearly this needed an internal solution.
French and British front ends and tuners, 1951-1954
Developments in France and Britain during the first half of the 1950-ies were different from those in the CCIR-B countries Netherlands, Western Germany, Scandinavia, Switzerland, Italy and (with modifications) Belgium. The main reason for this were the unique and local standards: 405 lines in the UK, 819 lines in France, with limited need, desire or possibility to receive TV transmissions with different standards. Furthermore, since both countries were large it took longer to obtain full coverage, and new transmitters were often far apart; e.g. in France the order was Paris, Lille, Strasbourg, Lyon and Marseille. Only in 1956 did the roll out of more regional transmitters start. Britain had a similar roll-out. Because all stations transmitted the same program, owners of a TV set were expected to select the strongest one for reception, and TV sets were thus assumed to need only a one-channel receiver. In practise this meant that a basic TV chassis could be equipped with a set of channel-specific coils in the factory, making it a regional receiver. When owners moved home to another region the TV set had to be modified to the new regional frequencies in a service workshop.
Until 1950 the RF front ends of the television front ends were all based on dual pentode solutions, two times UF42, EF42 or EF80. We've seen earlier that the performance of these tuners was mediocre at best. The first to introduce a more dedicated valve was the French tuner development. Linked to the roll out of the new 819-line standard from 1951, with its 14MHz channel bandwidth, a much better performance was required, and a new front end based on two ECC81's was introduced. Remember that the AT7501 tuner introduced simultaneously in Eindhoven only used the ECC81 for the mixer-oscillator. Also this French front end was the first to introduce the cascode input circuit.
At the same time it was not a tuner, but a fixed single-channel front end, built on the main chassis of the television. This concept was introduced in 1951 with the TF652A, the first Philips 819-line set developed in France, followed by the TF2323 rear projection TV and then the TF1420 and 1720 platform, the local version of the TX1410. But the "single channel front end on the chassis" concept came to an end, and in 1952 the front end function - still not a multi-channel tuner! - became available as a module or bloc monocanal, but still based on an almost identical circuit diagram. These blocs were factory-aligned for a single specific channel, and could easily be exchanged when needed. Initially a single model was required, serving French channel F8a (vision carrier 185,25MHz) of the Paris and Lille transmitters, later the Strasbourg version for channel F6 (174,30MHz) came available. In parallel the bloc also introduced the final French IF values, but these will be explained further down. In 1954/55, with the TF1746, the bloc monocanal was replaced by a then standard 12-channel tuner module. |
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In the UK developments were similar, although not identical. Like in France the front end function remained initially on the main chassis, where the British Mullard-designed chassis tended to have two separate chassis sections: one for small signal (RF up to video output) and one for large signal (synchronization, deflection and HV generation). The design remained based on the two EF80's, so not using the cascode input stage. Channel-specific implementations were made using three replaceable coil modules. These modules fitted in standard B9A/Noval valve sockets, were factory-aligned and colour coded, and during set alignment they were not to be touched or changed. Modification of a TV set from one regional channel to another thus meant replacing the three coil modules. This concept was used from 1951 (the 1100 family) until 1953/54 (1400 and 1700 families). By that time a customer could choose between basic modules with the single-channel frontend or optional 12-channel tuners (the AT7520).
All in all it is surprising to see that in both the UK and France the Mullard and La Radiotechnique TV design centres were much more conservative in introducing higher IF values and/or multi-channel tuners compared to their colleagues in Eindhoven and Krefeld. The main explanation for the multi-channel tuner is probably that, due to the deviating 405 and 819-line standards, there was not even the possibility to receive transmissions from other countries, this in contrast to Germany, the Netherlands, Belgium and Switzerland which all had neighbouring countries with (almost) identical standards and programs that people wanted to receive. In France and Britain there was initially only one program transmitted, without the need for multi-channel tuners. Tuners were only introduced once multiple programs were transmitted, especially in the VHF-III band.
Tuner basics 3 - Choice of Intermediate Frequency
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Circuit basics, the cascode pre-amplifier PCC84
Electrically the main innovation in the next tuner family was the introduction of the cascode input stage, based on the new PCC84 dual triode. In contrast to the EF80 so far used in tuners, the PCC84 was developed specifically for the tuner cascode pre-amplifier role. It featured two completely separate triodes (no common cathode for example) with a screen in between. The screen was connected to the grid of the second triode, which would be RF grounded. Parasitics were kept as low as possible to allow operation across the VHF-III band between 174 and 216MHz; the input capacitance of triode 1 (Cgk) was only 2,3pF and the very critical feedback capacitance from anode to grid (Cag) only 1,1pF. The triodes could both operate at relative low anode voltages of 80-90V and still provide a good transconductance of 6mA/V. This in turn allowed that from a DC perspective two triodes could be stacked and fed by a 165-180V supply voltage, each of the two then operating at half that anode-to-cathode voltage.
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The basic characteristics of the dual triode cascode circuit is explained using Figure 6. S2 is the secondary winding of the input impedance matching transformer, where the 250-300Ohm antenna impedance is transformed upwards to the roughly 3kOhm input impedance of the first triode. Cag is the feedback capacitance from anode to grid of the triode, while Cgk is the input capacitance. By adding C3 and C7 of equal value as Cag and Cgk a Weatstone bridge is created that will prevent spurious oscillator signals to radiate out of the antenna. This is often referred to as neutralisation of the anode capacitance
One of the first main difference of the cascode to a standard triode or pentode input amplifier is the gain. The gain of a triode amplifier is gm*Rl, with gm the valve's transconductance in mA/V and Rl the load resistance. But because the first triode looks into the cathode of the 2nd (identical) triode, the load resistance of the first triode is the input resistance of the grounded-grid triode. Which is 1/gm ! This means that the voltage gain of the first triode is gm*1/gm=1. The main advantage of this is that the Miller-capacity, the virtual feedback capacity Cag(Miller) = (1+A)*Cag(intrinsic), is minimal and remains almost equal to the intrinsic Cag. This in turn guarantees a wideband input, covering the entire VHF-I and III bands.
One of the first main difference of the cascode to a standard triode or pentode input amplifier is the gain. The gain of a triode amplifier is gm*Rl, with gm the valve's transconductance in mA/V and Rl the load resistance. But because the first triode looks into the cathode of the 2nd (identical) triode, the load resistance of the first triode is the input resistance of the grounded-grid triode. Which is 1/gm ! This means that the voltage gain of the first triode is gm*1/gm=1. The main advantage of this is that the Miller-capacity, the virtual feedback capacity Cag(Miller) = (1+A)*Cag(intrinsic), is minimal and remains almost equal to the intrinsic Cag. This in turn guarantees a wideband input, covering the entire VHF-I and III bands.
The input signal of the 2nd triode Uk will be amplified - in-phase! - with gm*Rl, where Rl this time is the resonance resistance of the output bandpass filter S5-C4. The second triode thus provides the amplification. Noise of the 2nd triode appearing at its cathode will be voltage divided with the internal resistance of the first triode looking into the anode. This gives typically a 7 times reduction, which means that the equivalent noise contribution of the 2nd triode at the input of the first triode is only 15% of the total. The total Noise Figure of the PCC84 input stage came to 5-5,5dB, giving roughly halve the noise of the EF80 with its 8dB NF.
Finally, between the 1st and 2nd triode a resonant bandpass circuit is made using the inductor S10, which, in combination with the first triode output parasitic Cak and the 2nd triode input parasitic Cgk, resonates at the VHF-III band centre frequency around 195MHz. At VHF-I frequencies the inductance of S10 is reduced by a factor 4 and the circuit reduces to a low pass filter.
Finally, between the 1st and 2nd triode a resonant bandpass circuit is made using the inductor S10, which, in combination with the first triode output parasitic Cak and the 2nd triode input parasitic Cgk, resonates at the VHF-III band centre frequency around 195MHz. At VHF-I frequencies the inductance of S10 is reduced by a factor 4 and the circuit reduces to a low pass filter.
Tuner basics 4 - Automatic Gain Control (AGC)
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AT7530, introduction of the drum tuner, 1953
As mentioned, the AT5701 tuner family of 10-channel continuous capacitive tuning modules had some serious limitations, the most important of which was the bad noise performance due to the EF80 pentode pre-amplifier. But secondly tuning was always manual when the user changed channels, tuning through the entire band. Thirdly, but this is only an assumption, stability of the bandwidth characteristics must have been questionable given the continuous tuning of both the channel filter and the LO. Where these elements already demanded for a new tuner design, there was furthermore the need to shift the IF to the new higher values around 30-45MHz. All this resulted in the AT7530 family of tuners, that introduced quite a number of new features:
- the cascode input low noise amplifier, using the PCC84 dual triode optimized for RF performance
- the PCF80 mixer-oscillator, where the mixer pentode gives a higher isolation of the IF
- IF at higher, newly standardized frequencies in the 30-45MHz range
- different regional versions based on the same basic design, but aligned for the different standards
- the mechanical drum tuner concept, with up to 12 pre-set channels in the VHF-I and -III bands
- separate knob for fine tuning
- variable gain as part of an Automatic Gain Control loop
The known members of the Philips AT7530 tuner family, showing the different models with respect to covered channels and the IF standards. The models starting with A3 696 52 introduced a slightly modified electrical design, mainly related to biasing. A3 models are from Eindhoven, MK from Mitcham (UK), PK from Monza (It) and FD from Dreux (F). Non-standard valves are highlighted in yellow: 6U8=PCF80, 6CW7=ECC84, 6BL8=ECF80. In the last column bold text indicates Belgian multi-norm chassis versions.
This tuner family also introduced the first multi-norm tuners, for use in the 17TX100 and 17TX110 series for especially Belgium and French border zones. These tuners, like the AT7550, used the same picture IF of 38,9MHz as the regular CCIR-B versions, but required an extended channel bandwidth to accommodate the 13MHz channel bandwidth of the French 819-line standard. The sound carrier thus appeared at either 33,4 or 27,75MHz. With the drum tuner concept, using the optimized channel filter sub-modules, these type of customizations became a lot easier. The same method was applied for the NTSC and Italian standards, both using IF picture carriers around 46MHz, and Australian tuners with a lower picture carrier at 36MHz. Interestingly, in Australia, where the AT7580 was sold to the television manufacturer Kriesler, the tuner was modified to 6,3V parallel heater supply, using the 6CW7=ECC84 and 6BL8=ECF80 equivalents of the PCC84 and PCF80.
In 1954 the A3 696 52 introduced slight modifications in the biasing of especially the PCC84 triodes that would be carried over into the next generation (circuit A'). |
Four views of the A3 696 52 tuner. From left the top view; the drum with 10 channel filter modules mounted and two vacant; interior view from the bottom, with on the right the spring contacts for the drum (nrs 1-12 in the previous picture). At the top C18 is the fine tuning capacitor for the oscillator, which is operated by the outer ring of the control knob; a sideways interior view. [Philips 21TD140A Service Manual]
For options 3 and 4 the tuners were equipped with two connectors that were compatible with the Noval sockets of the EF80's and coil filter modules of the original single-channel frontend. The 1st plug used the original EF80 pre-amp socket and connected the tuner to the 180V and heater supplies, the 2nd used the BPF coil socket and connected the IF output of the tuner to the chassis IF signal chain. A third plug contained a damping resistor for the now unused oscillator tank circuit coil. In the TV set the second MO EF80, which was left inside, now became an extra IF amplifier.
Only in 1955 the TV tuner was consistently introduced in British sets, and no longer as an option. These tuners re-used the mechanics of the AT7520 and 30, but had on two aspects a quite different electrical design approach. The first was the biasing of the cascode. Where the Eindhoven design used classical resistor-based DC biasing of the upper triode grid to set all current s and voltages in the cascode, the Mullard design used a kind of floating biasing scheme. Here the cathode current of the upper triode through a 120 Ohm cathode resistor R3 sets the upper grid voltage through R2. The second difference is the rather unique balanced IF output, using a coupled transformer. This was already applied in the AT7522 above, possibly to provide better transfer characteristics of the fairly long IF output connection.
In parallel with the introduction of the tuner came an important concept change: the IF finally moved into the 30MHz range and became in line with the BREMA requirements: 34,65MHz picture carrier, 38,15MHz sound carrier. |
There is one more oddity, which I have conveniently put into this family, although strictly spoken it is not: the A9 022 78. To start, this is the only known tuner using the valve combination PCC84-PCC85. It is completely unclear why this design was used, other than a modest cost reduction compared to the PCF80. The circuit diagram was identical to the AT7530. However, there was one more odd characteristic: it used a VIF of 40,4MHz and a SIF of 34,8 (B/C/D) or 29,15MHz (F), values not seen in any other set. The reason for this is totally unclear, but probably related to the fact that this tuner was intended for third party set makers in Belgium CBRT (Brugge), ACEC (Charleroi) and Sierra. Possibly these were the IF values used by these set makers in their 4-norm televisions. The single Aristona model using this tuner was then probably an ODM model from CBRT. A9 was a Philips Service code, also indicating a different relation with the set maker than the internal fabs.
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Tuner Basics 5: French and Belgian multi-norm reception
The UK, being an island, could comfortably select a deviating TV standard, since there were simply no adjacent countries within reach with transmissions using different standards (we conveniently ignore the few thousand people along the Channel and on Guernsey and Jersey that could receive French channels). For France the situation was quite different, being surrounded by countries transmitting mostly CCIR-B signals (Germany, Switzerland, Italy and Spain). Neighbouring Belgium and Luxembourg had on the one hand made token compromises on their standards, but for all practical purposes these standards were still closer to CCIR-B than to the 819-line CCIR-E. In the broad swath of roughly 100km left and right of the French borders there was thus the need for multi-standard receivers and similarly along the Belgian borders. To complicate matters further, the French 819-line high-definition standard with 13,15MHz channel bandwidth used overlapping channels with inverted frequency arrangement; odd channels had a low picture carrier and higher sound carrier, the even channels high picture carrier and lower sound carrier.
To tackle these complexities essentially three tuner and IF arrangements have been used during the 1950-ies:
A. early French front ends and tuners using dual IF frequencies
B. French drum tuners with constant IF frequencies (but inverted compared to the standard tuners)
C. Belgian multi-norm tuners and IF
To tackle these complexities essentially three tuner and IF arrangements have been used during the 1950-ies:
A. early French front ends and tuners using dual IF frequencies
B. French drum tuners with constant IF frequencies (but inverted compared to the standard tuners)
C. Belgian multi-norm tuners and IF
Before diving into the tuner specifics we need a quick look at the French channel arrangement, as shown left. To allow sufficient 13,15MHz wide channels in the VHF TV band the odd and even channels were inverted as shown, where the sound carrier frequencies of one set were located on the channel separation of the other set (see the dotted lines). Another oddity was channel 8A of the Paris and Lille transmitters. This channel was defined before the channel definitions were finalized and was shifted with respect to the standard channel raster. All in all a much more complex arrangement than the CCIR-A or -B standards.
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The first generation ECC81 and PCC84 blocs monocanals and tuners consistently used the LO above the wanted channel. As a result an odd and even channel appeared inverted in the IF domain, see the example for odd channel F7 and even channel F8 in Figure 12. Note that the LO-frequency for channel F7 is identical to the picture carrier of channel F12, and the LO for channel 8 to the sound carrier of channel F11. This was done to avoid disturbing beats in case of interfering channels.
The consequence of this arrangement was that the sets required double-tuned IF chains, so 28,05 and 35,7MHz for the picture and 24,55 and 39,2 for the sound IF. For details on these sets see Piet's Home-built Television pt2. Also note that the total IF bandwidth was 15,15MHz, 2MHz wider than the channel bandwidth. This architecture was used in the TF1730 and TF1740 families. |
For the next generation French tuner and TVs a cheaper concept was chosen, starting with the FD 90 001 drum tuner, part of the AT7530 tuner family, and TF1750 set from 1955. For the odd channels now a low LO was used, resulting in identical video and sound IF carrier frequencies for all channels, see the example for channels F8 and F9 in Figure 13. In all cases the LO frequencies are identical to the opposite sound carriers.
The only difference with conventional CCIR-B tuners was the low picture carrier IF, an arrangement also used in British tuners. In both cases this was almost certainly chosen to avoid problems with interference from the lowest channel 1 picture carrier (in the French case F2 with picture carrier 41,25MHz). |
A third way of receiving French channels was used in the Philips 4-norm receivers for Belgium. As explained earlier, these sets were able to receive standard CCIR-B (Dutch or German channels), CCIR-C (Belgium Flanders, with AM sound), CCIR-F (Belgium Wallonie, 819 lines, 7MHz channel, AM sound) next to the standard French CCIR-E. Here Philips decided on a common video IF carrier of 38,9MHz, requiring another up-down inversion of the French channel LO frequencies. In the IF a switchable IF bandwidth was used between 7 and 8,5MHz. This meant that for the French signals some 2MHz of the upper video frequency range was sacrificed, which shouldn't have given any picture quality problems.
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In closing we'll have a last look at the IF of multi-norm receivers. Figure 15 shows the video (only!) IF characteristics. At the top the IF frequency characteristic of standard CCIR-B/C/F signals, where the only difference is the modulation format of the sound (AM or FM) or the line rate (625 vs 819 lines). In the video line up typically blocking filters are located at the adjacent N-1 sound carrier (40,4MHz) and N+1 picture carrier (31,9MHz). For the video (!) the sound carrier is of course also filtered out (at 33,4MHz) to avoid sound-to-video picture distortion. The result is the centre graph, showing the video IF passband in a Philips multi-norm receiver. For the French 819-line reception the video IF characteristics were essentially left unchanged except for the 33,4MHz filter that was removed because the sound was much lower at 27,75MHz. This resulted in the lower IF graph, with a -3dB bandwidth of roughly 5,5MHz, still substantially lower than the transmitted 10,5MHz video bandwidth.
Sound was treated differently. In the first 21TX100 and 21TX110 receivers the sound IF was separated from the video immediately at the output of the tuner, resulting in a dual frequency IF: either 33,4MHz (B/C/F) or 27,75MHz (E). These were down-converted a second time using an oscillator of 40,4MHz (B/C/F) or 20,75MHz (F), resulting in a 7MHz 2nd IF for further sound demodulation. From the TX170 the CCIR-B FM was using intercarrier sound at 5,5MHz which was used for FM demodulation, the AM sound being processed separately. This scheme was used well into the 1960-ies, when new methods emerged. |
Philips 4-norm televisions, 1953-1961
From the very beginning Philips has put a very high priority on the Belgian 4-norm sets. Although they were primarily designed for the complicated Belgian situation with four standards (B/C/D/E), derived versions were needed on essentially all border areas of France: Germany and Spain (B/E) and Switzerland (B/E plus the Italian IF for B). Finding solutions for these areas, and being able to position Philips as the solution provider for all areas, was deemed extremely important. But such a solution was a challenge, which seems to have been given to the Natuurkundig Laboratorium Research organisation in Eindhoven, probably in close cooperation with the Apparaten-lab a few buildings down the road. This resulted in the TX100 chassis, which is described in detail earlier. It was together with the contemporary TX1420 and TX1720 the first chassis using the new AT7530 family of tuners. Philips was so proud of this solution that it appeared, together with the new tuner, in the prestigious Philips Technical Review magazine, albeit only in 1955. The different characteristics of the TX100 are summarized below.
After the success of the TX100 chassis, almost one in three chassis throughout the 1950s and early 1960s was a 4-norm solution, undoubtedly contributing to the broad acceptance of Philips as a leading set maker. The changes between these successive chassis were predominantly in two domains: the audio and efforts to automate the norm selection.
The TX170 introduced a new architecture for the sound. The Gerber-norm B FM sound IF was taken after the video detector as intercarrier sound, using two UF80 and PCF80 valves for amplification and three OA81 Germanium diodes for FM detection. The sound IF for the AM systems C/D/E was still taken directly at the the tuner output, amplified using three UF80 valves and then peak detected using two OA81 diodes. A norm-dependent switch then selected the detector outputs from either branch. The TX170 chassis was derived from the TX140, still suing the same frame mounted on a wooden carrier, and with the tuner in front of the chassis. It was followed by the TX220, TX230 and TX240 chassis in 1958-59, all still using the same internal chassis but equipped with the latest AT7632 tuner and a new cabinet style. The TX170-220-230-240 used 25 valves, the highest count for any of the 1950s Philips chassis, and an illustration of the complexity. And this was after further drastic measures, e.g replacing the four UY85 supply rectifier valves in the previous TX144 chassis by four AA250 Selenium power diodes, otherwise the count would have been 29 on a comparable basis. (From the TX220 chassis these bulky Se rectifiers were replaced by two OA210 Germanium power diodes).
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The TX280, which appeared already the next year in 1959, saw another sound channel simplification. While still using 5,5MHz intercarrier for FM and 33,4 and 27,75MHz for the AM IF, these now shared the same IF amplifiers. A switchable BPF in the anode of the first IF amplifier was made of two stacked resonant circuits at 5,5MHz (for the intercarrier) and 27,75MHz (the French 819 lines IF). When receiving either of the two Belgian standards, part of the upper inductor was short-circuited to ground, shifting the resonant peak to the 33,4MHz IF. In the meantime the TX280 had moved to the same chassis architecture as the TX250, using a 110degrees CRT and the same frame layout. However, there was no room for the tuner, which was therefore placed higher up on a small platform. This platform also contained the new norm switch, now operated by a large knob on the side of the set. Six different rotary switch assemblies operated six Bowden-cables that ran to the different sub switches on the chassis. A third norm-related innovation was the automatic 625-819 line switching. A dedicated circuit around a PCF80 received the separated sync pulses from the regular synchronisation separator. These pulses are fed to a resonant circuit tuned to the 625-line 15.625kHz, and the output (negatively) peak detected. In case of a detected 15.625kHz signal the PCF80 triode is squeezed and the current through the relay blocked. For 819 lines the relay is active. The contacts operated by this relay were used inside the line and frame deflection branches.
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The last step in these VHF-only 4-norm receivers was introduced with the TX300 chassis from 1961. Electrically everything remained identical to the TX280 as described. But the manual norm selection switch was now replaced by motor-control. To this end a standard setting rotating assembly was added, which - through Bowden cables - rotated synchronized with the VHF drum tuner. It also had twelve positions, and for each position (=channel) a notch could be set to N-B-F. These notches operated a three-position electrical switch, which in turn determined how far the motor-controlled norm switch would be rotated. Although this was a major ease-of-use improvement compared to the manual operation, the drawback remained that for each channel the norm had to be set at the back of the TV set.
All in all the 4-norm set remained a complex engineering challenge, but a continuing series of innovations made this a highly successful segment for Philips. |
The Philips Television organisation, 1950-1960
Section removed.
The Radiobuizen-Lab or Dammers-Lab
Throughout the story up to now it is clear that tuner module development and key component (valve) development went hand in hand, because tuner performance was almost one-to-one related to valve characteristics. As we've already seen in the story on early TV development (here, here and here), the group responsible for (amongst others) the specification and development of new TV valves was the Radiobuizen-Lab (Radio Valve Lab) located initially on the 4th floor of the Witte Dame building (EF4) along the Emmasingel in central Eindhoven. The group responsible for Consumer Valves, serving radio and TV applications, was led by Bert Dammers, the boss of my father when working there, and as explained earlier a brilliant designer of innovative valve-circuit combinations. He was personally at the basis of the success of the Philips television, radio valves and even the tuner businesses. As a consequence of the broader television growth, both in sets and components, also the RBL Consumer Group continued to grow, led by Dammers. In 1956 he became the head of the entire lab, covering both Consumer and Professional groups, and the lab was subsequently usually referred to as the "Dammers-Lab". In the meantime it moved to the first floor (EF1) in the Witte Dame.
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During the early 1950s the RBL Consumer Group was undoubtedly occupied with the improvement of the many TV functions, driving for more advanced valves that would either reduce cost (often by integrating functions into combi-valves like triode-pentodes) or increase performance (e.g. the series of improved power pentodes like the EL86 for audio and the PL84 for the line output). Frame grid valve developments will definitely have been part of the activities, leading to the improved RF valves used in the tuners.
PCC88 the first frame grid valve, 1956
Section removed.
Philips Tuner naming and coding
Section removed.
KR 361 52 family with the PCC88, 1956
In principle the new PCC88-based tuner had the same circuit diagram as the previous AT7530 generation, including the slight biasing modifications of the upper cascode triode (the two resistors forming the voltage divider for the grid voltage were increased from 10ok and 120kOhm to 820k and 1MOhm, possibly to provide higher isolation of the oscillator signal through the power supply lines). To allow a "deeper" gain control of the input triode, the main change in the design was the introduction of a series cathode resistor of the input triode, R4 of 120 Ohm and RF decoupled by C11 of 820pF. This put the cathode DC voltage to almost 3V at Vgk=0V. Finally as can be seen on the circuit diagram, the now separate screen of the PCC88 was directly grounded to earth, while an RF bead was introduced in the anode feedback capacitor C7 to avoid oscillations. The oscillator and mixer circuits around the PCF80 remained unchanged, including the galvanic output coupling.
With the growth of the television business also tuner production spread towards the different television factories. The latest PCC88 family saw the introduction of tuners from Krefeld (Germany) and Monza (Italy). At least in the case of Krefeld the tuners were not straightforward copies of the Eindhoven tuners (coded A3 768 xx) but introduced some design modifications:
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Circuit diagram of the Philips A3 768 xx 12-channel drum tuner, introducing the PCC88 RF triode. This circuit will be referred to as "Circuit B". Circuit changes compared to "A" are highlighted. The dotted line has been added for clarity, representing the magnetic coupling between the S5-S6 BPF and S7 oscillator tank circuit, which is responsible for the oscillator voltage injection into the PCF80 mixer pentode grid. [Philips A3 768 24 Service Manual]
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Overview of the known models of the A3 768 15 Philips tuner family, the first to introduce the PCC88 valve. These tuners still used the first generation rectangular box containing the drum mechanism. A3 are Netherlands models, KR are from Krefeld (BRD), FR from Dreux (France) and PK from Monza (It). The EA9143 was produced by the Z-factory in Barcelona (Spain), a Philips subsidiary. TV product codes in the last column in bold indicate 4-norm sets for Belgium, France and Switserland. Especially in remote countries like Australia the change-over between generations was different, using later valves in combination with the old mechanics.
Tuner basics 6: Automatic Frequency Control (AFC)
Section removed.
AT7630, new mechanics, 1958
In 1958, more or less in parallel with the introduction of UHF tuners, the VHF tuner underwent some changes, introduced as the AT7630 family. In contrast to earlier innovations these changes were pre-dominantly mechanical:
- a new module housing, with the bottom sides slanted inwards, roughly following the contours of the revolving drum inside. This was undoubtedly a materials saving measure, since the two lower areas of the tuner were unused. This basic form factor was to have a long life, even surviving the introduction of transistors and only to be replaced in the early 1970-ies.
- printed coils on the channel-specific "biscuits" used in the revolving drum. This was again a cost saving, avoiding the costly manual labour of assembling the many different precision air coil assemblies. Challenges with the new concept were most probably the accurate trial-and-error definition of the proper inductive values of the printed coils, the lower Q (quality factor) of printed inductors versus air coils, and space. Especially for the low frequency coils the challenge was undoubtedly to obtain sufficient inductance with as many as possible windings on the limited available area of the biscuits printed circuit board (PCB). Also, compared to the standard PCB technology introduced for the main electronic board in TV's, these tuner biscuits required substantially finer traces and thus a more accurate printing and etching technology.
- Memomatic, an innovative mechanical construction to store the fine tuning setting for each of the 12 channels individually.
It seems that the printed coils were not introduced from the very first models in this new generation of tuners, so the AT7630-7633 were probably still using discrete coil "biscuits" like the previous generation. But rather quickly versions with printed coils appeared, starting with the AT7634. From the picture below it is clear that for the largest coils, with the highest number of windings, a fairly fine pitch PCB technology was required.
Before we turn to the Memomatic, a quick glance at the circuit diagram of the AT7630 family. First order there were not many changes compared to the final circuit C from the KR 361 51 generation, but we will code the new basic circuit as D1:
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Towards the end of the 1950-ies the number of transmitted VHF channels increased rapidly. One consequence of this was the move to UHF, that will be discussed in the next chapter. A second, quite different effect, was the need to "remember" channel tuning conditions when changing between channels. Don't forget that with the television sets as they were at the time, the channel selector was a large rotary knob mostly on the side of the cabinet, with an outer ring for the fine tuning. Every time the viewer changed channel this had to be done manually, first selecting the channel, then the fine tuning. Over the coming years we will see many efforts to make channel selection easier. Since there was no way to store data electronically all these solutions were invariably mechanical by nature. The first one was the Memomatic or (in German) Memomatik.
The core concept of the Memomatic was to use a small bolt per channel (the orange arrow) for fine tuning, i.e. the setting of the oscillator tank circuit trimming capacitor C23. The tip of the bolt pushed a cantilever (orange, turning around the red axis) which pushed the core of the tuning capacitor C23 inside the box. Every channel has its own bolt, which were positioned on a circular plate on the central axis, 12 in total. The bolt was set once per channel, after which it was in the right position every time the channel was selected, acting as a mechanical memory.
A consequence of the new Memomatic mechanical construction was that it was deemed impractical to maintain the primary channel rotation know on the same front side of the module. As a consequence this function was "diverted" from the front to back face of the module through a set of beams and gear wheels, indicated in blue on the mechanical drawing. The Memomatic was thus an impressive mechanical piece of engineering, a first of more to follow. Despite the complexity, which hopefully didn't cause any reliability issues, and the associated higher cost, the Memomatic seems to have been a success, since it became a widely used feature in many successive tuner and TV generations. At the same time it could easily be deleted and replaced by a standard tuner, making it an interesting commercial selling feature. |
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A complete Memomatic tuning unit is shown on the left, a module from 1960 in most probably the 21TX310 or 21TD310. Above is an AT7637 or A3 300 40 VHF tuner, mounted horizontally on top of a first generation UHF tuner. Although the picture doesn't show the complete construction with respect to the control, it is clearly visible that the wheel on top is used for the VHF drum rotation as described earlier. The wheel lowest left is for the UHF tuning. Looking at the construction it is almost certain that the per channel fine tuning using the 12 screws had to be done by a service engineer, given that they don't seem accessible by the television set user.
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The table with the overview of the (initial) AT7630 family of VHF tuners shows a continuous expansion compared to the previous generations. Especially French and Belgian multi-norm solutions gave an increasing diversity, mainly due to the channels used. Halfway the entire family came the upgrades to the cheaper printed coil biscuits as well as the Memomatic option. And finally there were the locally produced tuners like in Italy and the UK.
And before closing this chapter it is interesting to get a glimpse at the prices of these tuners, form a September 1960 price list of Philips components for electronic hobbyists. It shows the AT7632 for Hfl60,00 an the AT7635 for Hfl65,00, confirming they were after the picture tube the most expensive electronic components. For comparison the complete high-voltage line output unit was Hfl30 and the deflection coil unit Hfl25. (The Hfl60 must have been around 60DM, 1200BFR, 180FF, 20GBP and 30USD at the time). Another source, however, mentions the price of the AT7635/80 (with Memomatic) as Hfl14,75, suggesting that the hobby price was 4 times the normal factory price. |
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Update history
August 2017
1st upload
October 2022
Added paragraph on Vision IF standardization, mainly based on discussions and input Steve "Synchrodyne" on Vintage Radio & TV Electronics Forum
October 2023
Due to the release of the Philips Technology History volume1, covering the 1950-1980 tuner history, the page has been reduced to the core tuner generations story. All background information can be found in the book.
1st upload
October 2022
Added paragraph on Vision IF standardization, mainly based on discussions and input Steve "Synchrodyne" on Vintage Radio & TV Electronics Forum
October 2023
Due to the release of the Philips Technology History volume1, covering the 1950-1980 tuner history, the page has been reduced to the core tuner generations story. All background information can be found in the book.