Answer to "Always shows error of paper jam"cat pee is acidic. this must have caused some parts in the board to corrode and shorted out
Answer to "Why does my amp not produce a sound from the instrument's signal?"you could try checking for bad opamp/buffer chips near the input jacks.
Answer to "When I power on my pc, the light comes on for a second, then goes out."replace the power supply unit. this should be an easy job because the psu uses plugs that are simply inserted in and out.the plugs and sockets are also clearly marked corresponding to each other.replacement psu are quiet inexpensive and easy to obtain .