Radiomobile 4200

[innellan House]

Last year, I acquired a 401. It is negatively earthed. The original radio and clock are not connected, presumably because they are positive ground. The radio is a Radiomobile 4200, and I cannot see any provision provided to switch its polarity. However, I understand that one can use a DC-DC converter, as a device to reverse polarity......so that the original radio or clock may still be used. Does anyone have practical experience of installing such a device?