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Q2 and Q1 form a sort of video op-amp. The video gain of this amplifier is the ratio of R8 (4.7k) divided by the video gain pot value (R3). You can see that if R3 is set to half way (500 ohms) the gain is about 10 times, which means you are already trying to get 10 volts of video out of Q1, which only has a 9 volt supply! So - the circuit is cheapened by not having another resistor in series with R3 to limit its minimum value. Starting point for R3 setting should be at max resistance, and only adjust to a lower value if you are not getting enough contrast.
R7 (BIAS) should NOT be adjusted for all black video conditions as the article states - its real purpose is to prevent getting zero-carrier clipping on whites. It has a similar problem to R3, in that it should be limited so you couldn't go to zero resistance. Always start with this pot at max resistance, and only adjust it as needed to prevent white clipping and sound buzz. Note that at zero resistance it shorts out the input to Q2 and the feedback from Q1 - very bad for operation.
Regarding the RF output transistor, I can't guess immediately from the diagram what the dissipation is. However, the output transistors should be driven class C by the RF oscillator, while the video modulates the collector voltage. This circuit is expected to generate harmonics, much of which are supposed to be filtered out by C12, L1, and C13. Scoping the collector directly will show harmonics to some degree even though c12 is right there. There should be less harmonics at the output on C13.
Regarding the sound, Q3 is a simple frequency-modulated oscillator, tuned to 4.5 Mhz nominal frequency by T1. The 4.5 MHz sound carrier is mixed with the video by R9 (10k ohm), so it is at about a 10% level compared to the video that comes in through R3. So, if you scope the emitter of Q1, you should see video of several volts (with sync positive, since Q2 is inverting), with 4.5 Mhz "fuzz" of about one-tenth the video amplitude riding on it. This combination is what modulates the collectors of the output transistor(s). (The capacitance of your scope probe may cause some distortion and amplitude reduction of the 4.5 mhz).
By the way, L3 (2.2 microhenry) is meant to prevent the RF from getting back into the video/audio circuit. How good it is in the real world, I don't know, so you might see some RF messing up your scope readings here too.
Another caution is on tuning the channel frequency. This circuit modulates double sideband, and you need to be careful that you have not accidentally tuned it to the next higher channel (channel 4 while trying to receive on channel 3, for example). You may get a recognizable picture but not a good one from receiving the lower sideband this way.
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