[Andrew2]

Nice cartridges these are, especially for a ceramic type which were looked down upon by the moving magnet brigade.
In the early 70's I had an SP25 Mk2 in which I fitted a new 9TAHC, but the audio from one channel was intermittent. Usually it could be coaxed back into life by a gentle touch on the stylus.
In the end it became such a pain I just went out and bought a new one, but that one was the same - on the other channel!
So both of them went back to Sonotone with a (long and very studenty) letter. A couple of weeks later I received two new cartridges and an explanation of the fault, which sadly my memory cannot recall.