The mod that we perform to the Oktava MK219 and MK319 is almost the same. The circuit and layout is very close and the same results are achieved.

• Mod the Grill to a more open and transparent brass wire mesh. In the 219, I cut out the grates across the capsule.
• Replace and bias the FET with a Neumann style fet.
• Two resistors are replaced with 1 Gigaohm resistors
• Replace the electrolytic capacitors with better capacitors.
• Replace the transformer coupling capacitor with a better capacitor.
• Retain the switches without adding capacitance ** (See citation below)
  
• Isolate the capsule from the capsule mount.
• Replace the wire with Mil. Spec.Teflon/ Silver coated stranded wire.
• Coat the interior of the body with a rubber compound. (Better than Silicone)
• Burn in the mic for three days and retest.

** mod inspired by Mark Fouxman, Samar Audio & Microphone Design

• Change two resistors out to 1 gigaohm resistors.
• Change the capsule coupling capacitor.
• Change select capacitors to improve frequency response and clarity.
• Change the FET to a Neumann style FET used in the U87 mic.
• Bias the FET to custom tune and optimize the performance of the microphone.