In a Yamaha TRS MS02 for a Yamaha Tyros 2 keyboard
3 ch , 19 pin hybrid chip. I cannot find the pinning . A 27MB SM out there
has full component level schema for the Tyros but not the powered speaker
add on . Strange use of screened signal lead carying the 2ch input signals,
to take 1ch back to the keyboard, separate lead for the other ch and woofer
in the box. I'm particularly after the standby or mute pin.
The STK433-240E is a different pinning, this one no suffix , ie not "A"
either. Cold tracing so maybe erroneous
-power p2
+power p3
ch A, p4+5 o/p
ch B, p6+7 op
gnd p9+10
p11 an input, assumed , as capacitor feed
p15 an i/p same C
p17 an i/p, same C
p18+19 chC, op
leaving 1,8,12,13,14,16 unplaced so far, LV supplies ? , FB ? etc