[Leon Crampin]

John, the circuit diagram supplied originally with the radio gives all the circuit references and the device type numbers. The information given above is broadly correct. T011 is listed as an AC121S but as stated above, it's not critical as it merely defines the inter-base voltage and hence the quiescent current of the output stage. A germanium device is needed to give a temperature coefficient with respect to voltage which matches the output pair. An AC128 would do.

You can make a reasonable check of these devices using the diode test facility on a DMM or an AVO on the Rx1 range. The b-e and b-c junctions should each test as a germanium diode with very little reverse leakage. Note than the AC187 is npn and will show reversed results.

There is a solder covered break in the track to T013 which allows the quiescent current to be set. It is important to ensure that the adjuster R650 is not intermittent - apply Servisol Super 10 and move the pot several times end to end before setting. The adjustment should give a quiescent current of 7.5 mA at a supply voltage of 9V (important - don't use the inbuilt power supply).

The other big weakness is the smoothing capacitor C806 which sees more than its rated 16V on 240V mains. Replace with a 2200uF 25V type, noting that there are 3 negative connections which need to be linked. A failure can cause damage if the 400mAT fuse is incorrectly substituted.

The tuning capacitor drive spindle bearing needs to be free (heat and light oil should do this) and the user push button switches will also need the Servisol treatment.

Good sets, well worth restoring.

Leon.