“It has been a long road from beginning to end.” Let's start at the beginning, the exploding television. I did some research on old TV's and what was inside them that could make them behave like a tpu, stumble on the correct frequency components to cause the phenomenon of magnetic collection and blow up, or implode, as the case may be. So basically these old set’s did consist of several interesting components. 1. The CRT (Cathode Ray Tube). 2. The Flyback Transformer. 3. The deflection coils. 4. Vacuum Tubes. I took a close look at those parts to see if they would fit in any of the ongoing Theory’s. 1. The CRT (Cathode Ray Tube). Some of the old television set’s used wide-band I and Q color demodulation for higher color resolution. Synchronous low level 1.5 MHz I demodulation and 0.5 MHz Q demodulation and phase splitting derived red, blue, and green signals by I, Q, and Y matrixing methods. Hmm, RGB Red Green Blue, this reminded me of Steven talking about 3 frequency’s. So I continued to read on: Color synchronization was achieved by a conventional AFC circuit with a phase detector and reactance control of a crystal oscillator. Hey, AFC circuit , Automatic frequency control circuit, phase detector, reactance control, crystal oscillator, sure sounds interesting…. Sounds like some sort of variable tuning device.... 2. The Flyback Transformer. Now when somebody says flyback I immediately think about the transformer in the picture above. However my view on that did quickly changed while reading further..... The flyback is a matching transformer that couples sweep energy from the class "C" power amplifier to the horizontal deflection yoke coils. In the early models, the flyback is an autotransformer. Taps on the autotransformer match the high impedance of the horizontal power-amplifier stage to the low impedance of the horizontal deflection yoke. Autotransformer?, now that is interesting because that is not a normal transformer, it does not have any galvanic isolation. Galvanic isolation is the principle of isolating functional sections of electric systems so that charge-carrying particles cannot move from one section to another, i.e. there is no electrical current flowing directly from one section to the next. Primary and secondary side have no electrical connection. Like this: An autotransformer is an electrical transformer with, Only one winding. The winding has at least three electrical connection points called taps. The voltage source is applied to two taps and the load is connected to two taps one of which is usually a common connection that is also connected to the source. Each tap corresponds to a different source or load voltage. In an autotransformer a portion of the same winding effectively acts as part of both the primary and secondary winding. Like this: The ratio of secondary to primary voltages is equal to the ratio of the number of turns of the winding they connect to. For example, connecting at the middle and bottom of the autotransformer will halve the voltage. Depending on the application, that portion of the winding used solely in the higher-voltage (lower current) portion may be wound with wire of a smaller gauge, though the entire winding is directly connected...... In three phase power transmission applications, autotransformers have the limitations of not suppressing harmonic currents and as acting as another source of ground fault currents. Hmmm, now that’s interesting. Anyway in the old televisions they looked like this: 3. The deflection coils. SWEEP Let's step into the fray when the electron beams are reaching the right side of the phosphor dot screen. The beams were deflected there by: (1) a magnetic field developed by (2) current flow through the horizontal deflection coils that is (3) controlled by the Class "C" 6CD6 power amplifier. In the above illustration, yellow highlighter traces a path of electron flow in a flyback circuit during this Final Two-Thirds of each horizontal trace. Below, red indicates typical current flow in a horizontal yoke during Retrace and the First-Third of the trace. When the electron beams reach the far right of the phosphor-dot screen, the power amplifier is cut off (current no longer flows along the yellow path), which collapses the magnetic fields. The whole horizontal output circuit breaks into oscillation from the shock, and the energy in the first half-cycle of oscillation drives the three beams back to the left of the phosphor-dot screen. The three beams flyback, or retrace, (get there) in about 7 microseconds. The horizontal oscillator and control system was called Synchro-Lock, and it used a 6K6 as a hartley sine-wave oscillator running at the horizontal line frequency, with a 6AC7 reactance modulator and a 6AL5 sync discriminator circuit backed up to the hartley through its transformer, with 1/2 a 6SN7 as the horizontal discharge and driver -that's a mouthful and that's the point. One half of that lone 6SN7 is a blocking oscillator. Frequency control of a blocking oscillator is fairly simple. To increase the frequency, for example, decrease bias on the grid. It will then take less time for the grid capacitor to discharge and drive the tube into brief conduction again. To accomplish frequency control, part of the horizontal drive signal is coupled from "D" on the blocking oscillator transformer, through 150kohm resistor 2R273 and 82-pF cap 2C246, to the grid of the control tube. A positive horizontal sync pulse is combined with the oscillator signal and the two affect how hard the control tube conducts. The harder the control tube conducts, the less negative the oscillator grid voltage becomes. That is beginning to look like frequency mixing with feedback…… 4. Vacuum Tubes. Here is a list of tubes and what they were used for: I also found out there was another intresting circuit onboard which is a so called AGC AMP. ( Automatic Gain Control ) Our objective is a TV picture of consistent contrast and quality, even though RF levels of the received television transmission vary considerably. To accomplish the objective, the gain of the receiver must be varied as the strength of the RF signal from the TV transmitter varies. To control gain automatically, the keyed Automatic Gain Control circuit needs a reference. It must know what the received signal strength is. Keyed AGC uses the amplitude of each horizontal sync pulse as an indication of signal strength. The same time a +365-volt pulse from the flyback whams the plate of the AGC AMP, a sample of the alreadydetected horizontal sync pulse is taken from the plate of the 1st video amplifier and applied to the control grid of the AGC AMP. If the sample is, say, MORE (or less) than the last sample, it will drive the grid of the AGC tube a bit MORE (or less) positive. That makes the tube conduct even MORE (or less). Which causes MORE (or less) charge to develop across C71. That in turn puts MORE (or less) negative charge across AGC filter capacitor C73. I hope some people will find this information useful, Turbo
