Main electrical wire cord and entry into the frame:

The wire (often insulated with «linen»)is almost in bad state, and must be replaced in many cases! If any doubt about the plug, replace it too. If the cable entry is directly into the frame, wire must pass into by means of a insulating rubber ring. Check it, and replace if destroyed. Take care at the wire cannot be tear out of the frame...

Main entry with connector:

If the entry is built with a little connector, and if in good state, leave it in place... Just replace the wire, if needed.

Transformer protection:

The supply transformer of each appliance must be protected against surges and short cuts. Size of the fuse is depending of the transformer power, not easy to evaluate. It's possible to know the approximative power of a transformer by looking at the numbers of tubes present in the radio... With 4-5 tubes, power is about 50W, it gives a 250mA fuse (for 230V supply). A radio with more tubes will have a bigger transformer, place a 500mA fuse. Those fuses will be slow-blow action.

Internal wiring:

Insulation of mains conductors inside the set must be checked, and the main switch too. Take care than some old radios were fitted with an auto-transformer: primary and secundary windings are connected, and the mains voltage is connected to the secundaries! Those radios are as dangerous as «all-currents» models, see bottom of this page!

Insulation test:

Faults (no contact between frame and conductors) can be checked with an ohm-meter, but a real insulation test must be done with a special tester, generating a high-voltage for testing. One of those testers on the photograph... Tube radios are class 1 appliances (needing earth connexion), the insulation must resist at 2120 Volts. This will not concern «all-curents» radios (or supplied by means of auto-transformer); see bottom... No current can flow between mains wires and frame! Your security depends of it!

You can see the building of a insulation tester (with schematic) on this site. Only in French, sorry...

Earth / ground connexion:

Old radios need earth connexion, for the security and for the «antenna flow». For this use, there is a plug hole on the frame. It's often interesting to made this connexion by means of the new power cord. Personally I use 3 wires cable and a 2 pole+ earth connexion plug. The green/yellow wire is used to link the frame and the earth connexion into the plug.

Mains capacitors:

Particularity in old radios is the presence of capacitors between the frame and the mains wires. In most cases, those are defective! Use here only Y1 or Y2 class capacitors: only those caps can be used between earth and mains lines. The capacity is limited at 4,7nF and are designed to never come in short-cut in case of failure. Never use here ordinary caps, or X - X1/X2 «mains» caps. Those are designed to be use only between mains lines!