If you want a really high quality replacement monitor for the NNC you have to build one up yourself. Its a process of hunting down a PFX or Toshiba chassis while at the same time doing your tube homework. There are several flat 29" tube #s that will work for the NNC, each of those tubes #'s will have a set of deflection yokes that will be compatible with the tube. Of those tube compatible yokes, there 'might' be one yoke that has compatible impedance measurements for the PFX or Tosh chassis (you managed to get one of those, right ?). So its a very narrow range of compatibility.
You got 2 options for getting the tube/yoke
1. Easiest but rarest - Find a 29" flat HDCRT, check model #s against CNET and look for 1080i or 480p. If you get lucky this will have a compatible tube AND yoke (ie Samsung TX-R2765). Then its just a matter of swapping connectors over for the deflection yoke and degauss connectors, and you are good to go.
2. Harder but more common - You find 29" flat CRTs that are not HD. You figure out the tube number, then google your ass off looking for an HDCRT that uses the same tube number, then if you are lucky/good you can get a service manual and pull a deflection yoke part #. Google the DY # and you might get lucky and find some Chinese CRT yoke reseller who has that deflection yoke. Then with some proxy buying luck you can get the HD yoke for your tube. Now comes the fiddly process of getting your purity perfect and then messing with convergence rings till you give up or are satisfied.
I mention going through all the trouble in step 2 of finding that exact right deflection yoke because it is really hard to get a CRT dialed in just right when doing yoke and ring swaps. It makes it even harder/impossible if the deflection yoke you are using isn't designed for the tube you have. You could mess with it forever and never get it right.
I was able to determine that the 'A68QCU770XV5' is a compatible tube (A68QCU770) and has a pretty much compatible deflection yoke (XV5)
I found a non HDCRT TV (Emerson?) with a A68QCU770X tube and some non compatible deflection yoke. I found the XV5 deflection yoke on Taobao and through some proxy buying was able to get that yoke. I have since fitted the yoke to the tube and pry have it about 90-95% perfect, so its still not a slam dunk when doing yoke swaps, even with a known compatible one. I can pry get that extra 5% by doing convergence strips but its just a lot of fiddling.
I did manage option 1 after about a year of dedicated CRT sleuthing, was $5 on OfferUp. Option 2 was $20 for the TV and I think ~$50 for the DY shipped to me.
