Demto is being modest. He did a lot of work modifying his Oktava mic and describing results, so his posts are good source material.
re: A step-by-step Oktava 319 cookbook -
If you search hard enough you will find an unauthorized copy of the article that Scott Dorsey wrote several years ago for Recording Magazine. I say unauthorized because this was a work-for-hire article Scott wrote and for which he recieves a royalty on reprints. I have to say the DIY mic modding community has been pretty respectful of his intellectual property rights and has not made this article widely available on the 'Net.
As a side bar to this article, I'd like to add that, in my opinion, Scott recommend fairly easy to find parts that would work in a plug n' play fashion and give some degree of improvement for DIY'ers with entry-level skills. This article does not represent the results of an exhaustive, multi-year R&D effort to re-design and remanufacture these mics to the highest possible performance levels.
For example - Scott recommended the use of the Toshiba 2SK170 FET because it can be dropped into the circuit and does not have to be individually biased. This is a fine approach for a DIY'er who doesn't have the spectral analysis and distortion measurement equipment to set the bias and opperating point of a FET for optimum performance. In fact, there are other devices in general and one device in particular that provides far superior transient response and detail than the 2SK170.
Likewise, the issue of "resonant bonk" reduction is not really addressed fully in Scott's article. The application of silicon RTV or felt to the body of an MK-219 or 319 is only marginally better than doing nothing. Finding a techique and materials to get 30dB of midrange "bonk" reduction took me years to acheive.
There are probably a dozen other examples where this helpful DIY article, written several years ago for a hobyist audience does not offer rigorous and comprehensive best-in-class solutions.
So I guess in summary I'm saying DIY is cool - I always support and encourage it. But don't expect to fine a cookbook-type recipe floating around the 'Net that is going to specify the part values, part types, part vendors and specialized procedures that will allow you to make a state-of-the art modification in a few hours of your spare time.
Cheers, Michael