A friend recently lent me a bass and amp on the condition I look at why the input jack crackles, pops and sometimes does nothing.
Turns out the solder joints on the 1/4" inputs had cracked and the connectors where loose.
It seems this is a common problem among Yorkville amps, as I have now just finished repairing a two more Yorkville amplifiers for this friend. These last two where a slightly different model, but the symptoms and problem were the same. Crackling, popping, dying inputs with fine cracks on the solder joints.
An hour of labour to disassemble, resolder, reassemble and test. Wish most fixes where this straight forward.