T-bone RB500 reribbon & upgrade

Ronnie at Diesel Studios in Italy sent in a pair of T-bone RB500 ribbon mics for service and upgrade. Ronnie asked for some photos of the process, and I thought they would make a nice photo-blog.

Here is one of the mics on arrival...

Inside the body, there is further screening to protect the ribbon, and the transformer sits in a metal can.

One of the old ribbons.

This one is not so great!

New 1.8 micrometer ribbons....

The old transformer has primary DC resistance of 90 milliohms, and 30 ohms for the secondary. Those laminations are not very well packed.

Winding new transformers for the mics.

Potting the transformers in the wax bath keeps the coils and laminations from vibrating....

The finished transformers. We may as well re-use the metal can for some extra screening.

Back together again