Yet another CRT Mod: Upgrade CRT RGB Drive Amps

[LukeEvansSimon]

One difference between very highend professional 15khz CRTs and low end consumer CRT TVs are the RGB drive amplifiers. These are straightforward NPN amplifier circuits, and checking Mouser and Digikey, more modern, significantly higher bandwidth NPN transistors exist for $1.5 for 3 transistors, which is all that is neesed... one for each color R, G, and B. This would be a higher bandwidth than even the transistors used in PVMs. The other benefit of these more modern transistors is they are more efficient and therefore use less power, generate less heat, and therefore do not need heat sinks and reduce the heat build up inside the CRT chassis.

Why do this? Well, higher bandwidth amplifiers take less time to move the CRT cathode voltages up and down, which is how color is controlled as the electron beam scans the phosphors. Video games can logically transition between colors instantly, but the RGB amps take time to transition the emissions of the R, G, and B cathodes. These drive amps are not swinging voltage up and down by a few volts... these amps have to swing the voltages by a couple hundred volts! A lower bandwidth RGB drive amp will have less sharp color transitions than a higher bandwidth amp.

It is not clear to me how visible the improvements would be to upgrade from 8mhz RGB drive amps to 500mhz RGB drive amps, but I am curious. Has anyone tried this before?

[Ikaruga11]

Pretty cool information. No idea but I'm interested.