On my Motorola Vt-71 I kind of understand how the high voltage is created. On your later mid-1950's sets like my Admiral 26R12,how is the high voltage created?<P>------------------<BR>Tony

The high voltage was generated by an osc. a 12SN7 and a power amp. 25L6 if I recall.<BR>It was not the "fly-back" system, but an osc. and step up "honeycomb"transformer air core.<BR>Been awhile since I worked on one.<BR>=====================================<P>------------------<BR>Bill Benson

Bill is correct.<P>------------------<BR>We improve things by making them worse...

The high voltage from all the 1950's sets comes from the "flyback transformer". This has to be one of the best inventions of all tv time, and I don't know when it was first used or who actually invented it. Almost all sets with magnetic deflection (for example the RCA 630) used it after WWII.<P>The flyback design uses the inductive kickback which is caused when the current through the horizontal deflection coil is stopped at the end of each scan line. This causes a big voltage spike which is further stepped up by the flyback transformer and then rectified for the crt high voltage. Another feature often associated with this design is the damper tube which keeps the horizontal circuit from oscilation and can supply an additional voltage source called the "boost".<P>These two features solve the problem of creating the high voltage and preventing unwanted oscilations while getting a higher B+ voltage source. All this from otherwise wasted energy and with very few extra components! Since the flyback system is syncronized with the horizontal retrace, there is no interfence generated like that created by the RF supplies. Pretty neat.<P>------------------<BR>

And nowdays, the flyback supplies many different voltages for your average TV.<P>------------------<BR>We improve things by making them worse...

The first set to use a flyback for HV was the German E1, made in 1939. It was also the first set to use a rectangular CRT:<BR> <A HREF="http://www.earlytelevision.org/e1.html" TARGET=_blank>http://www.earlytelevision.org/e1.html</A> <P>------------------<BR>

Thank you, Steve, for that interesting reference to the first flyback power supply. I followed your reference and got back to the German article which first anounced this. The link is <A HREF="http://www.xs4all.nl/~aobauer/FS%20Band1Heft6Dez39.pdf" TARGET=_blank>http://www.xs4all.nl/~aobauer/FS%20Band1Heft6Dez39.pdf</A> and the article begins on page 220. I read enough German to understand the basics of this article, but it is quite technical in the mathematics.<P>Here is the interesting part: The authors do not claim a new invention for deriving the HV source. Indeed, they write "Die Idee dieser Hochspannungserzeugunsart stammt von Farnsworth aus dem Jahre 1931" ---> "The idea for this method of producing high voltage comes from Farnsworth in the year 1931". The footnote references US Patent number 2051372 dated July 17, 1931. <P>The article goes on further to say (perhaps not exactly) "The implementaion of this idea presented numerous difficulties which caused the Americans not to adopt this method. The most important difficulties were: 1. The voltage is too low 2. The loading effect on the horizontal output...."<P>The article goes on to show a solution which I think (by now I am not really following the text and mathematics) involves the tuned flyback transformer. They also have diagrams (not fully legible) showing quad voltage multiplication to reach 30kv. <P>So, the basic idea of using the kickback voltage is Farnsworth's (1931). The first successful flyback system came from the Germans (1938). US manufacturers seemed to be a little slow on this one.<BR>--------<BR>Ron <P>------------------<BR>

I think American and British manufacturers hadn't reached the point with TV that they were attempting to reduce the cost of receivers, since even the smallest sets were out of the reach of all but very wealthy people. The E1, on the other hand, was designed to be as cheap as possible, so that it could be sold to average Germans and help spread Nazi propaganda.<P>------------------<BR>