Telefunken U-47 microphone refurbish project

Background

The Telefunken U47 tube condenser microphone is a well-known vintage studio microphone with a smooth and pleasant sound. It was introduced in the 1950s and quickly gained popularity in recording studios worldwide. Its exceptional ability to handle low frequencies, as well as its airy high-end and switchable cardioid/omnidirectional pattern, make it an excellent choice for both vocal and classical recordings. Additional information about this iconic microphone is available below. 

https://en.wikipedia.org/wiki/Neumann_U47

Although the manufacturing of these microphones and the V-14 Telefunken tube has ended a while back, there are still opportunities to purchase them, either as old or refurbished ones. Additionally, replicas that are built with newly made parts are also available. The three components that play a critical role in the original sound quality are the microphone capsule, the V-14 (M) tube, and the output transformer. Unfortunately, they are challenging to find, and if you come across original parts, they can be quite expensive. If you happen to have a non-functional U47 and can get your hands on spare parts, it is wise to repair it and either use it or sell it.

IMPORTANT WARNING:

Please be aware that the microphone and its cables contain lethal voltages. Failure to follow proper safety measures can result in serious injuries or even death. It's important to note that high DC voltages are particularly hazardous. Please take all necessary precautions to ensure your safety.

Fig.1 Main parts of the microphone before the build started. The black blob in the middle is the rare V-14 thermionic tube. It was originally designed for and used in WW2 field radios.