Kenwood KT-747L Tuner

This Tuner does not have any audio output. Probing its ckts with the
Oscilloscope showed that at two identical IC's marked 5223 5711 the
audio is present at one pin only. It looks like the system is in a
MUTE mode or the signal is not switched to the output-jacks. The front-
End and Tuning ckts are OK.
I cannot find any data on the IC's , schematic of the KT-747L would be
very helpfull.........
Is there anybody out here who has some knowledge on this receiver?
TY
Bram
.