[G6Tanuki]

The Germanium transistors used in these radios are prone to forming 'tin whiskers' with age, which causes an internal short-circuit.

This can be between the active electrodes of the transistor and the outer case. In your radio the outer case of the two output transistors is connected to earth via the copper heatsink-clips the transistors are fitted into - an internal 'tin whisker' short can therefore cause the transistors to pass an excessive current.

Try removing the copper heatsink-clip from its mounting screw and pulling it off the two transistors, so they are then left in free air. Then see if the problem continues.

[Note: if the radio then works, don't play it loud without the heatsink fitted, as the output transistors could overheat in other harmful ways].