aria bass amp AB-30 schematic

Merry Christmas. HoHoHo.

I know this may not be the best of moments to ask, but does anybody have a schematic for the Aria AB-30 bass amplifier? Its the one that looks like a cube type with the controls (1x input, 1x high/low white push button, 7 red knobs, 1x headphone out) on the top end.

I searched the www and then all forums and couldn't find anything.

The thing is that after using it for a while (3 minutes hard playing and 5-7 min. soft playing) it 1st switches off and on a few times in short sequence and then off definitively. I re-soldered all joints hoping that it is just a cold solder. Since the symptom remains I'm starting to thing it may be an electrical component.

Any ideas?