...since is 100% sure of flyback being damaged, I removed it from chassis, and discovered the real code from it. I assumed being the 15A1248-2, but is a code for the support, and forget to see the other side... the code is really the 79E77-9, from American chassis run -10 or -11, like Electronic_M said.
Here in the thread, Tim suggested the FLY-176 as a sub, and recently I found this link:
https://archive.org/stream/Thordarso...-1965_djvu.txt . Is very difficult to see the messy text, but confirms the FLY-176 as a sub.
Well, a month ago I contacted some people about this part. Only Moyer company responded that have a FLY-176 (the others don't have any compatible part), but then I not received response anymore... maybe they sell for a local client meanwhile, or some error in the catalog, who knows.
But anyway, since I suspect about the flyback secondary being the culprit about frying the part, I simply started an experiment: I removed the secondary entirely (and it shows signs of overheating), and connected a tripler directly to anode from 6DQ6. Normally we have a 4.5kV pulse here, so it translates to ~13.5kV to final anode, sufficient to work. Better will be a quadrupler, but then is needed to regulate voltage for not being >20kV.
With the absence of secondary, the tuning changes. I used a bench PSU for slowly watch the resulting +Boost voltage and the final voltage (using a color TV focus divider as a HV probe), and applying capacitors in parallel with yoke for compensating the tuning. Without any cap, the HV skyrockets and 6DQ6 arcs internally, and sweep is too narrow. A compromise was found, like I show in some photo here (small due to small maximum size here). I'm able to see a image!!! Hoorray!! (vertical not adjusted; more on this later).
A compromise between image line maximum size and is here, since one motive for high secondary pulse is the leakage inductance between primary and secondary, and with this process, this is absent. Too large a image horizontally, and HV downs too mutch, for example.
...but flyback starts to fry if I push it higher than 120mA cathode current, so I assume that the primary suffered some damage also. With 100mA it remais stable. At least it not smoke anymore...
This crazy experiment is motivated due to extra rarity of theses parts.