humming amp

amps used: fender princeton 112 plus and orange crush 10

my amps produce a terrible hum unless i plug them to 3-hole sockets. i only experience this when i use effects (chorus, delay, equalizer). no noise when i plug my guitar directly to the amp. i live in the philippines and not all power outlets have holes for the ground plug thats why i sometimes have to use a 3-prong-2 prong adapter when i bring any of my amps in gigs.

any remedies? ill appreciate any help.