I found FREE operating manuals for the amp & tuner here,
but the manuals just mention connecting the control cable between tuner and amp, not what they are for.
http://safemanuals.com/
I have found a Technics SU-X955 amplifier and connected the tuner to it,
it works fine without any control cable between them.
The reason why it did not work with the original amp was that there was no antenna connected to the tuner, and therefore no output, not even hiss. The tuner is dead...
I have picked up a Technics LW/MW/FM Stereo Tuner, model ST-X999L that someone dumped with his other HiFi equipment.
The unit appears to be in perfect working order but I cannot get to give an output to my amp, I suspect it is because it needs some control signal from the amplifier. This...