39XX Series Televisions
This short-lived range of models replaced the 3400 series chassis. Rapidly advancing technology meant that the new models were completely transistorised, allowing a marked reduction in power consumption over the 3400 which had still used ten valves. Because the transistorised circuitry was so much more compact, the new chassis allowed for new styling possibilities – some of the new models, the Beovision 3500 in particular, being no larger or heavier than a monochrome set of a few years previously. Text copyright © Beocentral. Unauthorised reproduction prohibited.
The 39XX chassis was all-new in design, though it continued to use the same Philips “phase II delta” tubes as the 3400 range. It included some up-to-the-minute features, such as a thyristor regulated power supply, solid-state EHT tripler, electronic tuning and a colour decoder that made extensive use of integrated circuits. In addition, it also featured a proper hi-fi audio amplifier of a similar design to that used in some of the smaller Beomaster models. The power that this required would have been considerable, so some was provided by tapping the waste energy from the geometry correction circuit. To complement this arrangement, a proper hi-fi loudspeaker was also fitted, housed in a sealed enclosure that was housed within but not part of the main cabinet. Text copyright © Beocentral. Unauthorised reproduction prohibited.
The greatest technical advance present in the 39XX series however, was in the colour circuitry. Previously, colour receivers included separate adjustment for each of the three electron guns in the tube to ensure that the light output at the screen was balanced, so that the grey scale, and thus the colour reproduction, was correct. These adjustments would drift as the tube and components aged, resulting in colour casts and impaired performance. In the 39XX, the performance of each gun was monitored and adjusted at the end of each picture frame, that is 50 times every second. The effect of this extra refinement was dramatic, with stable colour reproduction being possible throughout the life of the tube. This technique, known as “permanent colour truth”, has been a part of every Beovision CRT television ever since. Text copyright © Beocentral. Unauthorised reproduction prohibited.
Despite the use of the same tube as the 3400, the elaborate convergence circuits of old had been considerably simplified, and were now no more daunting that those of any other set of the period. Text copyright © Beocentral. Unauthorised reproduction prohibited.
Although the 39XX range represented a considerable technical advance over the sets that had been previously offered, it did not remain current for very long. Further improvements in manufacturing technology had produced a new type of tube, the “in line” type, which removed the need for many of the complex adjustments of the old “delta” type and required much less power. A version of this new type of type, the Philips 20AX, was the centrepiece of the 39XX’s successor, the 35XX series. Text copyright © Beocentral. Unauthorised reproduction prohibited.