[Vintage_RC]

There was one other test I had carried out which I forget to mention and which may move the investigation in a different direction. While Q3 was removed I injected a low level modulated 130KHz signal into each terminal of the IF transformer MF2 and the sound level from the speaker was monitored. The result was a healthy response at pin 6 but a very weak sound in the speaker when the signal was injected into pins 2 or 3. On reflection the O/P impedance of the sig gen is 50 ohms so there would have been a big mismatch which may have severely dampened the IF transformer.