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Originally Posted by Electronic M
If you tracked down a test jig with the impedance matching you could probably reverse engineer it. The 70's RCA jig I have supports everything from the 1955 RCA CTC-5 to stuff from the 90s according to the setup aeapter books the shop that used to own it sucribed to...
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Can you share schematics? Also, can you take impedance and inductance measurements of the transformers you have? We should take inspiration from the DIY tube audio, community and pull together DIY TV schematics as a community. Repair and restoration are only part of what is needed to keep tube television technology alive. Open source DIY schematics that can be simulated in LTspice would be an amazing educational tool for many.
One trend in CRT electromagnetic deflection technology was towards lower impedance, lower inductance yoke windings, as well as from series windings to parallel windings (which helps lower impedance and inductance). I don’t understand why that trend occurred though, but it appears to be aligned with the transition to solid state.
Basically, I want to back port many of the improvements that occurred in the solid state era to a pure tube chassis such as the improved yokes (better geometry), higher CRT G2, focus, and acceleration voltages (better focus and spot size), finer mask dot pitch, and smaller G1 aperture (smaller spot size).
Another improvement that I will try to back port: some of the compactron tubes that were designed for video amplification are small and lightweight enough to plug in to a printed circuit neckboard that has a design similar to a late 1990s solid state neckboard but with compactron amps as opposed to BJT transistors. The advantage would be reduced parasitic capacitance, inductance, and resistance in between the video amplifier output stage and the CRT cathodes. This would allow for higher video bandwidth at the same plate current, or, lower plate current at the same bandwidth. Lower plate current would prolong the tube amp’s lifespan.
I am torn on whether or not to cheat and use a 1990s DST flyback transformer. They have solid state rectifier diodes for the G2, focus, and high voltage anode lines. The majority of the tube audio community is OK with solid state power supplies, and keep the signal paths pure tube. Tube TVs have 2 power supplies: flyback power supply and B+ power supply. At first I will probably cheat and make those solid state, and later design non-solid state replacements. The non-solid state flyback power supply designs are very impressive, especially the ones that use a shunt diode tube for regulating the CRT’s high voltage. Most 1990s solid state TVs lacked high voltage regulation and yet pure tube TVs in the 1960s had it! A great example of newer tech sometimes taking a step backwards.