Radiometer Copenhagen OSG 42b Oscilloscope Repair, From The 1950’ish

The previous owner of this Danish vintage oscilloscope had tried to plug it in and the only result was smoke! I was asked if I wanted it for repair or it would be thrown out. The Radiometer Copenhagen OSG 42b was repaired and saved!

Radiometer is a Danish company from 1935, started by the engineers Børge Aagaard Nielsen and Carl Schrøder, to develop measuring devices for the growing radio industry in Denmark.

Radiometer OSG 42b controls, screen and inputs

This is not a complete teardown, but a repair, to save a nice piece of vintage Danish measurement equipment.

The inside reveals a beautiful construction technique. All tube sockets, strip lines and components are mounted on both sides of a base plate in the middle, with the CRT crossing through diagonally. High voltage transformer is located at the bottom and the input stage is shielded off from the rest.

It turned out that 4x dual 20uF/450V electrolytic capacitors were defective, one of them had sprayed its dielectric all over the inside. Bad capacitors or dried out capacitors is a very common cause of malfunction in old electronics like this. I replaced them with newer/desoldered 33uF/450V electrolytic capacitors. The small transformer would not be able to handle larger capacitance that we normally use in smooth capacitance in modern power supplies with less ripple.