Try switching your speaker cables from right to left and left to right. If the cut out moves to the left channel, then you have a short in the cables. If not, try switching the interconnects. This will prove if the cables are the culprit.
If you are still experiencing right channel cut out, then I would guess it's the capacitors in the amplifier.
If you are still experiencing right channel cut out, then I would guess it's the capacitors in the amplifier.