ElBartoME wrote:
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.
I need to find the time to get back to my CRT projects, but so many other things in life are taking up my time. The super neckboard PCB will come in two versions: one that uses the B10-277 socket, which will support most shadow mask tubes, and another that will use a socket to cover most aperture grille tubes. Because I mostly collect slot mask tubes, I am starting with the B10-277 version.
The super neckboard will also include a 70mhz bandwidth jungle chip: Texas Instrument's LM1203. So there will be two ways to wire up the super neckboard. You can wire it up to use the jungle chip already in your chassis, but if your chassis's jungle chip is not high bandwidth, then max resolution will be bottlenecked by it. The other way to wire it up will be to just have the input RGB signal feed straight to the LM1203 on the super neckboard. I found new old stock of LM1203s, so it will be low cost to include this feature. The disadvantage of using the LM1203 is that there is no on screen display, so pots on the neckboard have to be used to tune RGB bias (aka brightness) and gain (aka contrast). However, tuning these pots is only required once, during installation of the neckboard.
The biggest challenge for a CRT neckboard are the cathode amplifiers. Amplifying a 5 volt peak to peak signal up to a 200 volt peak to peak signal at 30 mhz bandwidth is impressive. Professional CRTs use smaller electron guns that run at a lower voltage than consumer CRTs that use electron guns that run at higher voltage. A PC CRT or BVM have cathodes that are run at around 50 volts peak to peak, whereas your consumer CRT TV has cathodes that are run at 200 volts peak to peak. The cathode amplifiers used in the large consumer HDTV CRTs are by far, more capable than the amplifiers used in BVMs. However, every CRT gamer knows that HDTV CRTs have horrible laggy circuits that are terrible for gaming. So my super neckboard is backporting the HDTV cathode amplifiers to 15khz SDTVs so we can have the best of both worlds: zero lag and yet ultra high bandwidth video amplication at consumer CRT high voltage.
ElBartoME wrote:
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.

It is important to preserve large curved consumer CRTs. The small PC CRTs and RGB monitors came into popularity very late in the era of CRTs, and yet many CRT gamers are trashing large curved consumer CRTs at a very high rate compared to the small PC CRTs and RGB monitors. As I mentioned above, the electron gun design and video amplifier design in pro CRTs are different than consumer CRTs. One is not superior to the other, just as a PS5 is not superior to a PS1.
The pot that is in series with R709 needs both a current rating and voltage rating to handle the increased current and voltage that it will need to endure if R709 is removed. So you can upgrade the pot too, in order to be safe.
Another model consumer CRT that would likely benefit greatly from this mod is the Mitsubishi CS-40809. It is a 40-inch bubble curved slot mask consumer CRT TV with component! However, the neckboard is designed to have the G1 voltage near zero and so the blank scanlines in 240p content are very thin. You can see a CRT gamer demonstrate the scanlines in
this YouTube video. Compared to the smaller 36-inch JVC D-Series, which is also a bubble curved slot mask tube, the Mitsubishi CS-40809's blank scanlines are no where near what they could achieve with a more negative G1 voltage.