Your custom neckboard sounds very interesting! Don't you need to adapt it to different sockets as not every tube uses the same pinout? How are you going to do that? I'm eager to see the results.LukeEvansSimon wrote:
Before I got distracted by family, work, other hobbies, and the US presidential election, I was working on designing and testing a from scratch new CRT neck board that uses a cathode amplifier design that has around 30 mhz chroma signal bandwidth for amplification of the RGB chroma signals up to 200 volts peak to peak. The design uses a "cascode" amplifier design, as well as Sanyo's discrete NPN transistor 2SC3782 that were used in 1080i HDTV CRTs. For generating the negative voltage rail for the G1, my "super neck board" design uses an inexpensive pulse transformer. This allows for tapping the unrectified cathode amplifier rail coming off of the flyback, to create a separate negative voltage rail that is 2x the voltage of the cathode amplifier rail (which is usually around 200 volts).
The idea is for the "super neck board" to take 5 minutes to install for somebody with beginner soldering skills, and by significantly increasing cathode amplifier bandwidth, further resolution improvements will be realized, in addition to those realized by increasing K to G1 and G2 to G1 voltage differentials. I've done all of the LTSpice simulations, ordered all of the parts, and I just need to breadboard prototype it now. I found a HUGE new old stock supply of 2SC3782 NPN transistors. Higher bandwidth transistors have been made since the 2SC3782, but they are not capable of the 200 volts peak to peak amplification that the 2SC3782 is capable of. The 2SC3782 is insane!
Also I'm debating on removing R709 so my G2 can go a bit higher. Not sure if this will cause any problems...
Theoretically I could use a voltage doubler and tap into the G2 voltage before it gets rectified but my concern is will this cause problems with the potentiometer for the screen voltage? It is not designed for that voltage and may arc. Also I'm not sure what the clearance is between G2 and G1. If I double G2 can this cause arcing between the two grids?
I have a Sony TV with a very worn tube. I might try doubling G2 on that TV before I accidentally kill my precious 34 inch Sony.