a continuance . . . .
The initial info was clarified by your confirmation that the system was indeed using that power IC.
Until you gave me the bottom of chassis foil pattern, it was not apparent that the manufacturer had deviated from that stock/data sheet schematic on the connections that were made and used with those 4 separate amplifier sections..
But, we now see that they opted to use different input/output sections, such that inputs 4 and 5 were used for the R+L inputs to then produce a bridged power output at 1 and 2 to drive to the sub woofer of the system.
That then left R and L inputs at 11 and 12 to then get power outputs to a Right and Left speaker pair.
This system was initially available as a high end soundsystem for Dell computers with 17 watts of power to each of a Right and Left speaker and a combined R+L 34watts to a central sub woofer.
Since you only seem to have what you have shown us . . . . . . .without case housing and the speakers ?
Particularly the satellite R and L speakers .
There just might be the possibility that at " end of life" , that this unit was performing intermittently or with one or more speakers not operating at all.
Using my photo if the POWER I.C. I can now clearly see that pins 1 and 2 are very solidly soldered to their foil solder pads.
I question the other solder connections to the square pins on further down toward pin 15.
Can you now VERY-VERY-VERY closely examine those other pin connections to confirm that there are being no "floaters" pins, in those 13 other connections.
I also need to know something of the two "knobs on one panel" ,of which, there is a large one and a smaller one.
Are both of them seeming to be rotatable controls . . .~ 270 degrees . . . . and is there any "click" type of action made at full CCW position . . .as signifying additionally incorporating a switch action ?
Or possibly,a pushbutton action was used, in which case that switch action would be created by push in, it locks in -push again- it pops out type of action from the knob.
Also can you confirm that my OVAL BLUE marked capacitors are being of an ~ 2200 ufd value ?
Stopping for feedback . . . . .
73's de Edd