So, I have this amp Epiphone Electar Tube 30. However, there was some milk, spilled into the input jack, and milk went all over the circuit board. At the first the amp wouldn't work anymore, then I waited a while, turn it on and it worked again. However, its a bit nosier, and dosen't sound as nice as it used too, so I was wondering is it ok If i wash the milk off the circuit board with a damp cloth then dry it again? Or do I have to buy a new amp?>
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dont ever turn the amp on when it is wet! as soon as something spills, unplug the amp, clean it, then let it dry before you attempt to use it. Your amp should be fine, just clean it up and you could use it again.
FS LTD EC-50 with GFS PowerRails Bridge pickup
..how do the milk get down the input?

try taking it in to get it professionally repaired at a music store, or at least see how much it would cost/whats wrong with it/if it's worth getting it fixed or just getting a new one.
There are harmful capacitors in there that could kill you if you try opening it... Take it to a tech.