A 21-year old Sony KP-53S35 TV we disassembled occupies a sweet spot for this curious electronics learner. It’s old enough that there are still discrete components we can look at, and new enough that information for those components can be found online. Here are two examples:
A Philips TDA6106Q is the most sophisticated looking component on the circuit board attached to the business end of the CRT. Datasheet says it is an amplifier, taking input voltage signal (0 to 8V) and amplifying it to a much higher voltage. (0 to 250V) It can handle signals almost up to 6 megahertz. The output pin of this chip can be traced to pin 8 of the tube. Best guess: this is how beam intensity is modulated to create a picture as the beam swept across the screen.
Components with big heat sinks always draw attention – they tend to be the most powerful components on the board. Either because they are doing a lot of complicated work, or that they are handling a lot of power. The circuit board with the power supply and high voltage transformer also had a pair of these STK392-110 units. The fact there were only two was curious: almost everything in a rear projection television comes in threes, one for each tube, what purpose would a pair of something serve?
Looking up STK392-110 gave us the answer on both fronts: they are high power amplifiers used for the purpose of controlling color convergence. The high power (over 100W) explains the heat sinks, and convergence control explains why there’s only two of them. If we’re working to make sure all three colors converge at the same places on screen, we could leave one color alone and just adjust the other two.
This seems to be a commodity part used by many rear projection televisions, and their high power handling meant they do burn out. As a consequence there are replacement modules still available for purchase at very affordable prices. Unfortunately the market is large enough for there to be counterfeit items as well.