Brian Gaff wrote:

Most of these are digitally tuned and the modulators in these computers
tend to drift. In the old sets the afc followed the drift, but not the newer
models. Often, its better to wire up a monitor lead and get the sound out as
audio.

No, it's not the modulator - I get it on the audio out too. And I don't
think it's the amplifier either, as a tone from a signal generator on
the right pin of the sound chip socket comes through very clearly.

Daniele